Electrical Lecture on Coke Pusher Cars

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Lecture Notes on Coal Loading and Coke Pushing Vehicle (Electric). The coal loading and coke pushing vehicle is the main machine used in side-loading coal solidifying coke ovens; it is responsible for tasks such as receiving coal from beneath the coal tower, carrying coal cakes, opening and closing the side doors of the oven, pushing out coke, and loading coal. I. Operating procedures for the coal loading and coke pushing vehicle: 1. The vehicle moves to beneath the coal tower, aligning the coal chute with the rammer on the solidifying machine; at this point, the front shield and the movable wall of the coal chute are in closed position. 2. The coal cakes are solidified, after which they are lifted to the highest position by the rammer. 3. Move the coke pushing vehicle to the carbonization chamber where coke extraction is to take place, and align the coal feeding device with the center of the carbonization chamber. 4. Activate the sliding door cylinder to move the coal feeding device forward so that it presses against the furnace door; then use the upper and lower screwing machines to loosen the bolts holding the crossbars of the furnace door. After that, activate the door lifting cylinder to lift the furnace door by 10–45 mm, after which the cylinder can be retracted. 5. Once the furnace door is open, operate the coal loading and coke pushing vehicle to align the coke pushing tip with the center of the carbonization chamber. The coke pushing operation can be carried out only after a signal to push the coke is given from the coke side or the furnace length. 6. Once the coke pushing operation is complete, start the coal loading and coke pushing vehicle in order to align the coal loading device (coal hopper) with the carbonization chamber. Move the inner and outer walls of the coal hopper back by 30 mm; the front cover of the coal hopper can be opened only when the signal light comes on. Coal loading can be carried out only after the furnace side or the furnace manager gives the signal to allow coal loading. After coal loading is complete, close the front baffle of the coal hopper, and then close the movable wall 7 of the coal hopper. After coal has been loaded, start the coal-loading and coke-removing vehicle, align the door-opening mechanism with the center of the carbonization chamber, actuate the door-moving cylinder to move the furnace door toward the carbonization chamber, lower the furnace door, and then use the upper and lower screwing machines to tighten the bolts holding the furnace door in place. Actuate the door-moving cylinder again to return the door-opening mechanism to its original position. Once the furnace door is closed, one cycle of operation for the carbonization chamber is completed. II. Electrical wiring of the coal-loading and coke-removing vehicle. 1. Traveling system of the coal loading and coke pushing vehicle. 2. Coal loading and coke pushing car door opening system. 3. Coke pushing system of coal loading and coke pushing vehicle. 4. Coal loading system for the coal-loading and coke pushing vehicle. 5. Coal loading and coke pushing car auxiliary system. III. Instructions for interlocking among various systems. a) Coal loading and coke pushing car traveling system. The traveling mechanism consists of four sets of centralized drive systems, each controlled by two Schneider frequency converters (ATV-68C10N4 AC380V, 75KW 142A) to drive the corresponding variable-frequency speed-regulated motors. The traveling speed can be adjusted within the range of 7.5 to 75 m/min. In the event that one of the drive systems fails, the other systems can still operate normally, ensuring the proper functioning of the coal loading and coke pushing vehicle. The drive for movement is based on gears, with all components being sealed for protection. The traveling balance vehicle features a 90° bearing structure, and its driving transmission uses hydraulic push rod brakes, offering flexibility and reliability as well as facilitating the alignment of the furnace door. Drive motor YZB255M-6, 30KW. Interlocking: Inverter start-up: ㈠ Conditions for powering the main circuit: ⑴ Main circuit breaker QF1 (QF2) is closed; ⑵ Contactors KM1 (KM4) are closed, as well as SA2 on the control panel. ㈡ Start signal for the control circuit: An output from KM1 (KM4) provides the start signal to the inverter. ※ Important: Interlocking with other mechanisms: rear limit switch of the coke pusher, rear limit switch of the door, lock switch of the rear partition, movable wall switch of the coal hopper, and hammer being in its original position. b) Coal loading and coke pushing car door system. The door operation system is a comprehensive system integrating electrical components, hydraulics, and PLCs. The main limits include: the rear limit for the door opening mechanism, the detection of the door lift hook, and the limits for fast and slow door opening speeds. The main interlocks of the door handling system are as follows: no movement. Key parameters: screwing motor with 2.2 KW power, tightening torque of 1200 N·m, loosening torque of 1400 N·m; maximum swing of the crosshead is 50 mm; total travel of the door lifting hook is 150 mm. c) Coke pushing system of the coal loading and coke pushing vehicle. The coke pushing system is an electrical control system. Interlock between the coke pushing system and other mechanisms: no movement, post-door opening limit, door hook detection. The limits of the coke pushing system include those on the main control panel: front limit, rear limit, front deceleration point, rear deceleration point, front extreme limit, and rear extreme limit. The eddy current brake is used in first and reverse gears, as well as for forward and reverse deceleration. During coke pushing (coal charging), an eddy current brake is used to regulate the speed throughout the entire process, thereby enabling impact-free coke pushing (coal charging). To prevent the coke pushing rod inside the furnace from being damaged due to sudden power outages or electrical failures, a manual device is installed on the planetary reducer. Under normal operation, the manual device is disengaged from the main rotating shaft; in case of a fault, gear meshing is used to pull the coke push rod out of the furnace. The braking of the coke pushing rod is achieved through an eddy current brake and a hydraulic push rod brake. Below, I will briefly explain the sequence for loading coal onto the coke pushing vehicle: Zero-position protection; the coal-moving bottom plate moves backward; the coal loading system operates in manual mode at I2.5; the switch for the coal loading system moves forward at I3.2; the coal loading system moves backward, as indicated by output Q4.1; the front shield opens at I5.5; the front limit of the coal loading system’s bottom plate is reached at I9.6; the interlock of the coal loading system is released at I3.0; the coal loading system moves forward, as indicated by output Q4.0; the rear shield of the coal loading system locks in place at I4.3; the switch for the coal loading system moves backward at I3.3; the back limit of the coal loading system’s bottom plate is reached at I9.7; the coal loading system’s bottom plate starts up again at I5.0; the interlock of the coal loading system is activated at I6.5; the coal-moving bottom plate moves forward; the coal loading system’s bottom plate moves forward (or backward), with the use of a time module to control the resistance levels; the switch for the coal loading system switches to the first level of resistance at I3.4; it switches to the second level of resistance at I3.5; to the third level at I3.6; and to the fourth level at I3.7; the coal loading system moves forward, as indicated by output Q4.0; the speed at the front end of the coal loading system decreases at I4.5; zero-position protection for the coal loading system is active at I3.1; the coal loading system moves backward, as indicated by output Q4.1; the second start-up of the coal loading system’s bottom plate is accompanied by a speed reduction at I4.6; the speed at the rear end of the coal loading system decreases at I4.7; the coal loading system’s bottom plate starts up again at I5.0; the rear shield of the coal loading system closes at I4.2; d) The coal loading system of the coke pushing vehicle. The limit points of the coal loading system include: front deceleration point, front limit, middle deceleration point, middle limit, rear deceleration point, and rear limit. The interlocks for moving the coal conveying plate forward include: front baffle opening, rear baffle opening after coal loading, front limit switch, no movement, rear limit switch after the door is opened, and overheating of the coal loading motor. e) Coal loading and coke pushing car auxiliary system. Auxiliary systems include: hydraulic station, air compressor, scraping trigger. IV. Precautions for operation. a) The maximum current during coke pushing shall not exceed the specified value of 350A, and the maximum current during coal loading shall not exceed 400A. If these limits are exceeded, it indicates an abnormal fault in the operation of the equipment. 4. Coke oven machinery: The coke oven machinery equipped in the 7m coke oven was developed based on advanced technologies from large-scale coke ovens both domestically and internationally, with the aim of improving operational efficiency, reducing labor intensity, and enhancing the working environment, following the principles of advancement, safety, and practicality. It has reached international advanced levels in terms of environmental protection control for coke ovens, automation level, high reliability, and low maintenance requirements. Each coke oven is equipped with one operator who operates it via the LCD touch screen of the industrial computer; an emergency operation panel is also provided, and the industrial computers are arranged in a dual-machine hot standby configuration. The coke oven is equipped with a operation management and oven number identification system. Based on the job plan and address signals transmitted by this system, the machinery of each coke oven can enable automatic movement and alignment of the vehicles. With an address detection accuracy of ±5 mm, the overall parking accuracy can reach ±10 mm. All operations within the coke oven machinery are equipped with comprehensive interlock controls; each unit is fitted with a fault alarm system, and interlocks are in place between the different units of the coke oven machinery. Reliable communication links, as well as data and information transmission systems, have been established between the various coke oven machines, and between these machines and the coke oven control room, the dry quenching control room, the coal charging dust removal ground station, and the coke discharge dust removal ground station. In addition to the “Job Management and Furnace Number Identification System,” the signal can also be transmitted via slip rings. The complete set of coke oven machinery operates according to a 5–2 coke pushing sequence, is controlled by unit programs, and is equipped with manual control devices. An emergency interlock device is installed between the coke pusher and the motor car. The main performance and features of the various coke oven machinery are described below. 4.1 Coal loading vehicle: The coal loading vehicle is a dust-removing type. Using single positioning, the devices and functions available are as follows: (1) Traveling device ； (2) Coal opening covers and guide sleeve devices ； (3) The feeding device is a screw feeder, equipped with a coal-sealing guide sleeve ； (4) The opening and closing of the coal tower’s discharge nozzle, as well as the operation for shaking the coal in the tower, are all controlled from the driver’s cabin ； (5) The gas collection system is equipped with automatic actuators; the coal loading vehicle can use these actuators to automatically close the water seal covers on the rise pipes in the gas collection system and to automatically open the water seal valves, as well as to switch to high-pressure ammonia solution, and to switch from the previous ammonia solution used in the furnace to low-pressure ammonia solution before loading coal ； (6) The dust collection system utilizes a combination of high-pressure ammonia water spraying and ground stations for dust removal during coal loading, and the coal loader is equipped with a sleeve that connects to the main dust collection pipeline on the coke side ； (7) The furnace top cleaning device is a mobile vacuum cleaner ； (8) The cab of the coal loading vehicle is located beneath the primary frame platform on the first floor; it features large windows that provide excellent visibility, allowing the driver to see in all directions. The driver’s cab and electrical compartment are equipped with stainless steel enclosures that provide insulation and are fitted with air conditioning. (9) The main technical parameters of the dust removal coal loading vehicle are as follows: Number of coal hoppers – 4; Coal loading method – screw feeding; Travel speed – approximately 90 m/min; Track gauge – 8270 mm; Total motor power – approximately 470 kW. 4.2 Pusher machine The pusher machine is equipped with the following devices and functions: (1) Traveling mechanism ； (2) Mechanized coke pushing device. The rack of the coke pusher is equipped with a compressed air cleaning system, and the coke pushing current is displayed and recorded automatically ； (3) Mechanized coal leveling device. The small furnace door of the flat-coal furnace is equipped with compressed air sealing guides to measure the excess coal collected during the flat-coaling process in each carbonization chamber ； (4) Furnace door opening and closing device. The door opening mechanism features a position detection and memory system (including detection and memory of the tilt angle and height position) to ensure good repeatability when opening and closing the furnace door, thereby preventing damage to the blade edges ； (5) Mechanized cleaning device for the machine-side furnace door and furnace door frame. To ensure reliability over long-term use, the furnace door cleaning device employs a combination of mechanical cleaning and high-pressure water cleaning ； (6) Collect and purify the dust escaping from the furnace door on the slave side ； (7) Head and tail coke recovery device ； (8) Device for purging the graphite at the base of the rising tube ； (9) Device for removing graphite from the top of the carbonization chamber ； (10) Mechanical cleaning device on the machine side control panel ； (11) Emergency measures in case of power outage. A diesel-driven mechanical pulling device controlled by manual operation and a PC system can be used to withdraw the coke pusher or coal leveling rod from the carbonization chamber ； (12) The main technical parameters of the coke pusher are as follows: Steel structure frame type – Gate type; Travel speed – Approximately 60 m/min; Track gauge – 14 m; Total motor power – Approximately 840 kW. 4.3 Coke stopper The coke stopper is equipped with the following devices and functions: (1) Traveling mechanism. The first rail is installed on the coke-side control panel, while the second rail is placed on the civil engineering framework outside the coke quenching vehicle’s tracks ； (2) Mechanized focus guiding device ； (3) Furnace door opening and closing device. The door opening mechanism features a position detection and memory system (including detection and memory of the tilt angle and height position) to ensure good repeatability when opening and closing the furnace door, thereby preventing damage to the blade edges ； (4) Mechanized cleaning device for the furnace door and door frame on the coke side. To ensure reliability over long-term use, the furnace door cleaning device employs a combination of mechanical cleaning and high-pressure water cleaning ； (5) Head and tail coke recovery device ； (6) Furnace bed cleaning device ； (7) Dust collection device. Dust collection hoods are installed above the coke-side furnace door, on both sides and at the top of the coke guide grid, as well as above the coke drum or coke quenching vehicle, to collect the dust generated during coke extraction and direct it into the dust collection main pipe ； (8) The main technical specifications of the coke stopper are as follows: Travel speed: approximately 60 m/min; Track gauge: 9010 mm; Total motor power: approximately 410 kW. 4.4 Motor car: This motor car operates on the tracks used for coke stopping on the coke side of the coke oven, and is used to pull and control coke cars or wet coke stopping cars. This motor car can meet the requirements of both dry quenching and wet quenching processes, and features fast operating speed, good speed control performance, accurate positioning, and operational safety. The main technical specifications of the locomotives are as follows: Number – 2 units (1 in operation and 1 as a spare); Vehicle type – two-story, fixed double-axle trolley type; Track gauge – 2108 mm; Track profile – QU100; Power supply – AC3P, 380 V, 50 Hz; Towing capacity – approximately 215 t (when the tank is full); Travel distance per trip – 90–305 m; Turnaround time for the locomotives – ≤8.7 minutes; Travel speeds – approximately 180, 60, and 10 m/min; Speed control method – variable frequency speed control (VVVF); Alignment accuracy of the locomotives – ±100 mm; Braking methods – energy consumption braking, disc braking, and air brake on the carrying vehicle; Air compressor – screw-type air compressor; Air conditioning units – one for each of the driver’s cab and the electrical compartment; Mechanical connection method – rigid pin connection; Air and electrical connections – quick connectors; Weight of the locomotives – approximately 45 t; Total power of the locomotives – approximately 300 kW. 4.5 Coke quenching vehicle: This vehicle uses a fixed-point method for receiving coke; its container doors open and close via pneumatic control. The container has a fixed inclined bottom, resulting in a simple structure that allows water to flow away quickly, thereby reducing the amount of water attached to the coke after it has been quenched. The main technical specifications of the coking car are as follows: track gauge – 2108 mm (center of the track); inclination angle of the coking car’s bottom plate – 28°; effective length of the coking car’s carriage – approximately 7500 mm; maximum effective capacity of the coking car (for dry coke) – 30 tons. 4.6 Coking tanks: A coking tank car consists of coking tanks and a transport vehicle, with a total weight of around 92 tons. The coking drum mainly consists of a drum body, lining plates, a swingable bottom gate, and a lifting rod that is connected to the bottom gate via guide rollers. The main technical specifications of the coking tanks are as follows: Number – 3 units (2 in use and 1 as a spare). Type of coking tank – Bottom gate operated in conjunction with a lifting rod. Shape – Circular. Structure – Welded structure made of steel sections and steel plates. Effective volume of the coking tank – Approximately 27.5 tons of coke. Weight of the coking tank – Approximately 40 tons. Main materials: The tank body is made of Q235-B; the lining plates are made of heat-resistant ductile iron and heat-resistant cast steel. Insulation material – Ceramic fiber pads. Bottom gate – Stainless steel.

4.7 Transport vehicles: These vehicles consist mainly of a trolley frame, a mechanism for rotating the coking tanks, and tracks for lifting and guiding the tanks. Their main technical specifications are as follows: Number – 3 units (2 in use and 1 as a spare). Structure – Saddle-shaped frame equipped with a mechanism for rotating the coking tanks. Structure – Welded structure made of steel sections and steel plates. Load capacity – Approximately 69 tons (when the tank is full). Rotation speed – Up to 7 rpm. Control method for rotation speed – VVVF. Motor used for rotation – Approximately 30 kW. Variable frequency speed control system for the overhead vehicles. By Xie Yong. Abstract: By making full use of the advancements in variable frequency speed control technology, general-purpose frequency converters are utilized in the speed control systems of overhead monorails. This approach enables thorough analysis and effective solutions to various technical issues related to vehicle starting, speed changing, and maintaining a constant speed. The system features advanced technology and high reliability, while reducing equipment costs and operation and maintenance expenses. ABSTRACT: Given the current technological advancements in VVVF technology, for the first time, a common inverter has been used in the drive system of single-track vehicles. This thesis analyzes in detail the technical challenges related to vehicle starting and speed control. The new control system offers high performance and reliability, while significantly reducing the costs associated with equipment, operation, and maintenance. 1. Introduction Riding the elevated sightseeing vehicles at Shenzhen Window of the World allows visitors to see famous sites from both ancient and modern times, as well as various exotic landscapes, making it one of the key attractions in the park. Through cooperation with Shenzhen Window of the World Co., Ltd., an advanced variable-frequency speed control system for overhead sightseeing vehicles was successfully developed. 　　Tourist buses frequently start, stop, go uphill, and go downhill while in operation; it is required that these actions be done smoothly and that the speed remain constant. The transmission control system is quite complex. As these vehicles are used to transport people, their operation must be safe and reliable. Moreover, due to exposure to sunlight and rain throughout the year, operating in harsh conditions, it is necessary that the variable frequency speed control devices have excellent performance and high reliability. 　　For transmission systems with high requirements for speed control, vector control systems with speed feedback have been used in the past, but they are expensive and difficult to maintain. Can it be achieved using a general-purpose frequency converter? Is it possible to keep a vehicle running at a constant speed without using a speed sensor? Based on the specific circumstances, through on-site inspections and analysis, we believe that it is entirely feasible to use Fuji’s latest FRENIC G9S series of general-purpose frequency converters. This is due to the development of AC variable-frequency speed control technology, which employs advanced control methods; as a result, not only is the speed control performance **improved**, but it also features intelligent functions such as parameter self-tuning and slip compensation control. II. System Solution The Fuji FRENIC G9S inverter boasts rich functions and excellent performance; it applies the concept of \"vector control\" to the operation of general-purpose inverters. It can automatically test motor parameters, calculate the motor’s output torque based on various load conditions, and then optimize the voltage and current vectors accordingly. Thanks to its high calculation accuracy and fast torque response, high-performance motor control can be achieved without the need for a speed sensor. 　　The power supply voltage for the elevated sightseeing vehicle is 3-phase 380V, supplied via cable busbars laid on the tracks through carbon brushes. There are 4 identical AC asynchronous variable-frequency motors, each driving one of the 4 wheels of the sightseeing vehicle. The track is circular and single-track, 450 mm wide, with a total length of 1800 m; the uphill and downhill sections each measure 300 m, and the maximum slope is 30°. There are 3 stations in total, and the travel time for the entire distance is about 15 minutes. The motor parameters are as follows: Rated power: 4.4 kW; Rated voltage: 380 V; Rated current: 11 A; Rated frequency: 40 Hz; Power factor: 0.76; Number of poles: 4. The total driving power of the tour vehicle is therefore 17.6 kW, with a total rated current of 44 A for the motors. However, calculations show that the 4.4 kW variable-frequency motor used is equivalent to a conventional motor with a rated power of 5.5 kW; accordingly, the total power of the four motors can be considered to be 22 kW. Since it is necessary not only to ensure that the sightseeing vehicle runs at full capacity, but also to be able to push a vehicle with a malfunction forward when such a vehicle appears ahead on the track, and to be able to restart the vehicle once it stops on an uphill slope, the capacity of the inverter must be chosen appropriately. The motor overload factor is generally 1.8 to 2.5, meaning the total current in the motor can reach 110A. After calculation and testing, it was decided to use one Fuji FRN37G9S-4 inverter, with a rated current of 75A and an overload capacity of 150% for 1 minute. An additional braking unit option is available to connect the brake resistor and enable braking functionality. The equipment selected is as follows: 1 frequency converter FRN37G9S-4, and 1 braking unit BU37-4B1. The brake resistors are installed under the tour vehicle to facilitate heat dissipation; they consist of 3 72Ω resistor units connected in parallel, resulting in a total resistance value of 24Ω for the brake resistors. 　　By utilizing the multi-level frequency setting function of the inverter, by setting the appropriate frequency values for each level and feeding the sensor detection signals through the inverter’s input terminals X1, X2, and X3, it is possible to easily achieve three speed levels required for the operation of the sightseeing vehicle: high speed for normal driving, medium speed when entering/exiting stations or on certain curves, and low speed when in manual mode. 　　Furthermore, the frequency detection signal FDT of the inverter, which is intended for motor brake control, has an open-collector output rather than a relay contact output, making it inconvenient to use. Since the relay contacts that generate the actuation commands AX1/AX2 on the power supply side are inactive, the AX1/AX2 signals on the inverter’s main control board are disconnected, while the FDT signal is connected to the drive circuit of the AX1/AX2 relays. As a result, AX1/AX2 become the relay contact outputs for the FDT signal. This eliminates the need for relay unit options, reduces system costs, and lowers the failure rate. III. Control Requirements and Measures According to the technical documentation for Fuji frequency converters, the main conditions for choosing torque vector control for the Fuji FRENIC 5000G9S/P9S frequency converter are as follows: one frequency converter can control only one motor, and it can be used in conjunction with motors of the same capacity or a lower capacity. Currently, the tour vehicle uses one inverter to control four motors, and the capacity of this inverter is two levels higher than the total capacity of those four motors. Is it possible to use torque vector control in this case? Can the technical requirements for vehicle operation be met? Since the frequency converters used in the tour vehicles are AC-DC-AC type voltage-based frequency converters, and the four motors have identical parameters and operate synchronously on the track, the frequency converters can fully utilize torque vector control if the parameters are set properly, thereby achieving their optimal performance. 　　The World Window elevated ride system operates autonomously, without a driver, running automatically under centralized monitoring. Appropriate sensor detection devices are installed on the tracks and vehicles to automatically control the entry/exit of the vehicles, as well as their acceleration/deceleration, and to ensure safety. Just as a car’s handling performance depends on its engine, the inverter, as the core component for driving and controlling tour vehicles, requires that its various parameters be not only calculated accurately but also adjusted repeatedly to achieve the optimal settings and thus the best performance. 　　The main operating modes of tour buses can be divided into: starting/accelerating, stopping/decelerating, traveling at a constant speed, and changing speeds. The requirements for the transmission control system and the corresponding technical measures are analyzed in detail below. Starting: To reduce the shock caused by acceleration/deceleration during starting/stopping, the inverter uses an S-curve acceleration/deceleration mode, allowing the output frequency to change smoothly in an S-curve pattern either when starting up and reaching the set frequency, or when decelerating and coming to a stop. This makes the start and stop of the tour bus very smooth, **improving the comfort for passengers. 　　According to literature, when motors are matched according to standard specifications and torque vector control is used, the inverter can achieve a high starting torque of over 150% at a setting of 1 Hz. However, during tests of restarting the vehicle while it was parked on an uphill section of the tour bus, it was found that the vehicle would first slide backward before accelerating forward, a phenomenon known as \"roll-back,\" and this occurred whether the test was conducted with an empty vehicle or with a loaded one. Despite repeated adjustments to the inverter parameters, this phenomenon could not be eliminated. 　　If the inverter uses V/F control, tests were also conducted on-site, and it was found that operation was acceptable when the vehicle was empty, but it could not start under full load with a steep slope, and this even caused severe vibration in the vehicle. This is because, under V/F control, the motor’s starting torque is insufficient; as the frequency output by the inverter increases gradually according to the set acceleration time, the motor remains stationary or even reverses direction, causing the motor current to rise rapidly. Under the current limitation feature of the inverter’s automatic acceleration function, the inverter reduces the output frequency and attempts to accelerate again, and this process repeats itself, resulting in vibration in the vehicle. It can be seen that the V/F control method cannot meet the requirements. 　　Based on this analysis, when torque vector control is used, although a \"sliding\" phenomenon occurs, the ride vehicle is still able to start smoothly. This indicates that the inverter can still generate sufficient torque output by the motor during low-frequency starting. The problem lies in the fact that it takes some time for the inverter to respond from receiving the start signal to enabling the motor to produce a high torque; as a result, at the beginning of startup, the voltage and current vectors are still being adjusted, and the torque output by the motor is insufficient, causing the vehicle to slide. This may not be a problem in most heavy-starting situations, but for tour buses, it is undesirable for there to be a loss of control and a descent. When the tour vehicle starts, the brakes are first released and then acceleration takes place gradually. The frequency detection function of the inverter can be utilized to set an appropriate frequency detection value, FDT LEVEL; when the output frequency exceeds this value, the FDT outputs an “ON” signal, which causes the brakes to be released. In this way, when the brake is released, the motor already possesses a certain driving torque, so the vehicle no longer slides down; this eliminates the phenomenon of \"vehicle rolling back.\" Even when pushing the vehicle or with it loaded, starting it again after stopping on an uphill slope is possible without any issues. 　　Stopping: When the tour vehicle receives a stop signal, the inverter gradually reduces the output frequency according to the set deceleration time, until the output is finally stopped. The setting of the deceleration time should be appropriate, ensuring that visitors feel comfortable while also allowing the vehicles to stop precisely in the designated areas upon entering the station, thereby preventing any instances of vehicles rushing past the designated stops. At the same time, to ensure the safety of vehicles and tourists, the tour bus should apply the brakes promptly after slowing down and stopping; otherwise, \"vehicle slippage\" may occur when stopping on slopes. However, the braking process requires a certain response time; therefore, the braking command should be issued in advance. When the output frequency drops to a certain value but has not yet reached 0Hz, the inverter sends out a \"zero-speed signal\" to command the motor to brake. “The “zero speed signal” is generated by the frequency detection signal FDT of the inverter. It can be set using the parameters FDT LEVEL for the frequency detection setpoint and FDT HYSTR for the lag amplitude of the frequency detection signal. Specifically, the frequency value of the “zero speed signal” is given by F ZERO = FDT LEVEL – FDT HYSTR. When the output frequency of the inverter falls below this value, FDT (which in this system corresponds to AX1/AX2) outputs an “OFF” signal. By calculating and testing the brake response time, and adjusting the frequency value of the \"zero-speed signal,\" it is possible to ensure that the ride vehicle slows down to zero while the brakes engage, thereby achieving the desired result. 　　Uphill: Under normal conditions, in the absence of speed feedback control, as the load on an asynchronous motor increases, the slip rate increases and the speed decreases. However, by using the slip compensation control function of the inverter, and by setting an appropriate slip compensation value based on the motor’s rated slip rate, when the motor’s load increases, the inverter automatically raises its output frequency, thereby keeping the motor’s speed essentially constant. Therefore, even when the tour bus is fully loaded and going uphill, its speed remains unchanged, just as it is when driving on flat ground. 　　Downhill: When driving downhill, under the effect of the vehicle’s own weight, the motor operates in generator mode, charging the main filter capacitor on the DC side of the inverter, thereby generating a braking torque. Inverter standards can provide 10–15% braking torque, while the use of braking units and braking resistor options enables 100% braking torque. When the voltage on the DC side of the inverter rises to a certain level, the braking unit activates automatically, connecting the brake resistors to enable energy-consuming braking, thereby controlling the monorail vehicle to move forward at a constant speed. Tests have shown that the vehicle speed remains stable when going downhill, and it can slow down properly and come to a stop even if it stops along the way. 　　After intense installation and debugging, the system was successfully put into trial operation. However, during the hot weather of summer, the frequency converter would occasionally experience an overheating \"OH1\" fault, resulting in shutdown. Due to the limitations of the interior space, despite efforts to improve cooling measures, the results remain insignificant. Therefore, the automatic energy-saving operation function of the inverter was set to active; this function automatically reduces the V/F curve under light-load conditions, thereby reducing the motor’s excitation current and motor losses and enabling energy-efficient operation, while also decreasing the inverter’s own losses. Since most of the track is flat, the load on the vehicle is low at this time. By using the automatic energy-saving operation function, the output current of the inverter decreases, resulting in reduced losses. During continuous operation, the temperature rise of the inverter drops significantly, and there are no longer any shutdowns caused by the \"OH1\" fault due to overheating of the inverter. IV. Conclusion The variable frequency speed control system for the World Window elevated monorail ride makes full use of the capabilities of general-purpose frequency converters, meeting all control requirements. It has successfully withstood severe conditions such as high temperatures, vibrations, and humidity, and operates well. Its advantages include: 1. Advanced technology The frequency converter features advanced torque vector control methods as well as numerous intelligent functions, enabling high-performance motor control, high accuracy in output frequency, and fast dynamic response. 2. Easy operation and maintenance: Since there is no need for a rotary encoder to provide speed feedback, the hardware of the control system is relatively simple. Additionally, the parameter settings for the frequency converter are intuitive, and the advanced fault diagnosis functions enable fast and accurate troubleshooting. 3. Reliable and safe operation: The frequency converter boasts high reliability and comprehensive protection functions. Application of Emerson’s DC Bus AC Variable Frequency Speed Control System | ________________________________________ 1 Load characteristics of the back-drive unit in horizontal spiral centrifuges The speed control device installed at the small shaft end of the differential gear of a horizontal spiral centrifuge is referred to as the back-drive unit. These devices include: eddy current brakes ； Asynchronous motor ； Hydraulic motor ； Mechanical overload protection devices (with the speed of the small shaft at zero), etc. When the screw lags behind the drum, these devices apply a braking torque to the small shaft at the cost of consuming the centrifugal mechanical energy, thereby achieving the purpose of adjusting the speed difference. For the small shaft, the back drive device represents a negative load. In a general-purpose frequency converter speed control system, the motor connected to the output shaft of the differential gear is in a regenerative mode for an extended period of time, operating in the fourth quadrant. It receives mechanical energy from the centrifuge, feeds the energy generated by regenerative braking back into the DC bus of the frequency converter, and then that energy is dissipated through brake resistors. How to recover this portion of energy is a matter of great concern to centrifuge manufacturers both at home and abroad. By using a specially designed four-quadrant drive inverter (such as ABB’s ACS611 inverter), the regenerated energy can be fed back directly into the power grid. However, inverters are expensive, and their use is limited to steel mills in China. The DS706 model of large-scale sewage treatment centrifuges produced by Alfa-Laval in recent years features a dual-frequency variable-speed energy feedback-based energy-saving frequency control system (using ACS800 series inverters), and they are currently in use at the **Ang Shun Chau Sewage Treatment Plant. In China as well, some manufacturers use domestic frequency converters to apply AC frequency conversion technology to common DC buses in horizontal spiral centrifuges, enabling the recovery of most of the energy involved, and thus achieving good social and economic benefits. The promotion and application of this technology are undoubtedly of great significance, and this article discusses it. 　　2 Structure and characteristics of the AC variable-frequency speed control system with common DC bus 　　1 – Main frequency converter ； 2-Main motor ； 3-Centrifuge ； 4-Differential ； 5-Auxiliary motor ； 6-Secondary frequency converter ； 　　Structure: The centrifuge 3 is driven by the main motor 2, with the differential pinion shaft being coaxially connected to the auxiliary motor 5. The speeds of the main and auxiliary motors are controlled by frequency converters 1 and 6; their DC buses are connected in parallel, with the three-phase power supply being supplied to the main frequency converter 1. 　　Features: (1) Excellent energy-saving performance: When there is a spiral hysteresis, the regenerated energy is sent to the DC bus of the auxiliary inverter. Since the DC buses of the main and auxiliary inverters are connected in parallel, this energy passes through the main inverter and is utilized by the main motor. 　　For simplicity, assuming that the centrifuge operates at a constant torque and constant differential speed in a steady state (ignoring the effects of acceleration and deceleration torques during speed regulation), the energy recovered is given by: P = 0.8Mn/9550, where P represents power in KW; M is the torque on the small shaft in N.m; n is the rotational speed of the small shaft in r/min. The factor of 0.8 before M takes into account the fact that during regenerative braking, even without the use of braking resistors for discharge, 20% of the copper losses within the motor are converted into braking torque. 　　(2) Fast dynamic response: Some PID control systems often exhibit overshoot and a long transition time; for example, in eddy current brake speed control systems, the stabilization period can sometimes last several minutes. The torque response time of the variable-frequency speed control system is only 150-200 ms, resulting in significantly improved dynamic performance. 　　(3) It is easy to deal with the accumulation of material inside the drum caused by emergencies: when the auxiliary motor operates in reverse, it is in the first quadrant (motor mode), at which time the speed difference is significant: Δn = (n1 + n)/i, where n1 is the drum’s rotation speed in r/min and i is the gear ratio of the differential. Thanks to the frequency converter’s static starting torque, which is twice the rated torque, it becomes easy to remove the material that has accumulated inside the drum. 　　(4) It facilitates constant torque control: Certain materials, such as municipal wastewater, contain 60%-70% organic matter. The sludge is compressible, and its solid content changes continuously, which causes the screw feeding torque to vary with fluctuations in the feed flow rate and solid content. Therefore, the electrical system must adjust the feed volume or rotational speed in a timely manner in response to these torque changes; otherwise, blockages are likely to occur. 　　The key to constant torque control is the real-time and continuous measurement of the screw thrust torque; it is necessary to select torque sensing elements appropriately. In the hydraulic motor speed control system, a fluid pressure transmitter is used ； In the eddy current brake speed control system, resistive strain gauge torque sensors are used ； In the frequency converter speed control system introduced in this article, the torque current analog signal output by the frequency converter can be used directly, eliminating the need to install separate sensors. 　　For example, the Emerson TD3000 inverter offers two operation modes: torque control and speed control. When torque control is selected, the output frequency of the inverter is automatically adjusted based on the output torque signal; when the torque required to push the sludge increases, the output frequency is reduced and the differential is increased, thereby pushing the sludge out of the drum more quickly ； Conversely, increasing the output frequency and reducing the differential increases the torque. This ultimately stabilizes the screw thrust torque around the set value. 　　3 Design of the speed control system 　　(1) Selection of the frequency converter: No special requirements are imposed on the main frequency converter, while the auxiliary frequency converter must be capable of suppressing input phase-loss protection. If the centrifuge requires constant torque control, a vector-controlled frequency converter should be used. 　　(2) Power matching of the main and auxiliary frequency converters: Not any frequency converter with arbitrary power can be connected as shown in Figure 1; when selecting the power of the main frequency converter, it is necessary to take into account the capacity of the auxiliary frequency converter to draw power from the main frequency converter when the auxiliary motor is in motor mode. 　　(3) Selection of auxiliary motor: The rated output torque of the auxiliary motor should be sufficient to meet the torque required for screw feeding. Since the torque M transmitted by the differential pinion is i times the screw feeding torque M2, the rated torque of the auxiliary motor should be greater than M2/i ； When performing the specific calculations, the adjustable range of the differential speed should be taken into account ； Factors such as the motor connection method. A standard three-phase asynchronous motor is used, with a speed control accuracy of 0.5%-0.1%; whereas an inverter-driven motor equipped with an encoder is employed, and when the inverter operates in PG vector control mode, the speed control accuracy can reach 0.1%-0.05%. Design example: Table 1 shows the power matching for the main and auxiliary inverters, as well as the selection of auxiliary motors, for more than a dozen different models of urban sewage treatment centrifuges in four series ranging from φ350 to φ720, produced by Haishen Mechanical and Electrical Factory. The main inverter uses Emerson TD2000, while the auxiliary inverters use Emerson TD3000. All auxiliary motors are 4-pole inverter-driven motors, equipped with OMRONE 6C2-CWZ6C type 600-wire optical encoders. 　　Taking the LW430W centrifuge as an example, its operating speed is n1=2200 r/min; the rated output torque of the differential is 4000–5000 N·m, with a gear ratio of i=91; the adjustment range for the differential speed is Δn=2–20 r/min (with a normal operating speed of 10–12 r/min). The auxiliary motor is directly connected to the small shaft of the differential, and the differential speed is calculated using Δn=(n1-n)/i. The values shown in Table 2 fully meet the process requirements. 　　The output torque decreases when the differential speed is below 7.7 r/min, as the variable-frequency motor operates in constant-torque mode below 50 Hz ； Above 50Hz, it is constant-power speed control; however, a low differential speed occurs only when the feed concentration is particularly low or at the beginning of feeding into the centrifuge, and the thrust torque is also low at such times. 　　4 Application Examples 　　Schematic diagram of the electrical control for the LW520 high-speed centrifuge used in the separation of soy protein extract. The main frequency converter U1 is used to drive the centrifuge, allowing its rotation speed to be adjusted continuously from 0 to 3500 r/min. The output frequency of the frequency converter is set via terminals X1 and X2. S1 is the switch for selecting the operating mode of the centrifuge; when S1 is set to position X1, the centrifuge operates at the separation frequency, while when it is set to position X2, it operates at the flushing frequency. The separation frequency is set to 45 Hz at the time of manufacture (drum speed: 3150 r/min), while the washing frequency is set to 5 Hz at the time of manufacture (drum speed: 350 r/min). If it is necessary to change these operating frequencies, the parameters F58 and F59 of the inverter can be adjusted. 　　U2 is an auxiliary frequency converter used to adjust the difference in speed between the centrifuge drum and the screw, that is, the differential speed. By changing this differential speed, it is possible to modify the speed at which sludge is pushed out by the centrifuge, which in turn affects the amount of sludge that can be processed per hour by the centrifuge. The DC buses of the main and auxiliary frequency converters in this machine are directly connected, resulting in excellent energy-saving effects. 　　PR is a speed display instrument used to show the speed of the centrifuge drum and the differential speed. There is a switch inside the tachometer used to select the synchronization alarm point; the options are 1 r/min, 5 r/min, and 10 r/min. When the speed difference falls below the set alarm value, the normally open contacts of the relay installed inside the tachometer close first, after which relay K1 activates and the auxiliary motor stops. Through the external contact of relay K1, the user can connect an audible alarm system, cut off the feed valve in case of an alarm, or communicate with a remote control system. 　　The time relay KT is used to address the issue of the low differential speed during the startup phase of the centrifuge, when this speed falls below the set alarm value. The advantages of this design lie not only in its simple circuit and easy operation, but also in the fast and accurate adjustment of the differential speed, with stability reaching ±0.1 r/min. 5 Conclusion The DC bus AC variable-frequency speed control system effectively solves the problem of recovering the regenerative energy from the drive motor of horizontal spiral centrifuges, bringing significant benefits to users. Taking the Longhua Water Treatment Plant in Shanghai as an example, it currently treats 100,000 tons of urban wastewater per year, using 2 LW430W centrifuges. Assuming a operating speed difference of 10 r/min and a torque on the small shaft of 15 N.m, it can be preliminarily estimated that one centrifuge can save 1.5 KW in energy consumption. With an operation time of 10 hours per day and 300 days per year, the annual energy savings amount to 4500 kWh. At a electricity cost of 0.631 yuan per kWh, the annual savings in electricity costs amount to 2839.5 yuan. The 2 centrifuges saved a total of 5,679 yuan in electricity costs. 　　This speed control system has strong viability and is worth promoting for widespread use. At this point, the fault should be identified and eliminated before proceeding with operations; forced overloading must not be attempted to avoid damaging the equipment. b) The pressure indicated by the oil pressure gauge in the hydraulic station should be within the range of 5–6 Mpa. c) During power outages or maintenance, the main electrical switch must be turned off, and all operation switches as well as the handles of the control panels must be in the zero position. d) During movement, the pusher rods, coal dragging plates, and door frames of the door-opening device must not move. e) The traveling mechanism must not move during coke pushing, coal loading, and door operation. V. Common Faults
1. The pusher car deviates from its intended path due to the zero-position switch malfunctioning.
2. The hydraulic system of the door-opening mechanism does not function (it works normally after the emergency stop button is reset).
3. The pusher car can still move forward even when the automatic selection is set to zero position (as K1 remains powered continuously).
4. The main gear shaft experiences excessive wear due to incorrect positioning of the pusher control, resulting in gear damage.
5. Power outage occurs because the scraper fails to make proper contact with the rails.
6. The coal-carrying bottom plate cannot move forward or backward.
7. There is no low-speed mode for loading coal.

Due to quality issues with the original control controllers (LK4—685 with a gear ratio of 1:30), many faults occurred. As a result, these original controllers were replaced with electronic control units such as GH6—06QDJ (with a gear ratio of 1:30 and 24V operation) and GH6—06QXJ (also with a gear ratio of 1:30). Now, faults related to the control controllers have been largely eliminated.

Previously, the No. 1 coal-loading pusher car could only load coal on the side of Furnace No. 1. Thanks to the combined efforts of our electrical and mechanical technicians, both No. 1 and No. 2 cars can now load coal for each other; similarly, the dust removal vehicle and the coke stopper vehicle can also operate together.

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Interlocked Control System for the Three Main Vehicles in Coking Ovens

With the continuous development of modern technology, new technological advancements are being applied more and more in the field of industrial process monitoring and control. This is also true in the coking industry. We know that without interlocked control, operating the three main vehicles in coking ovens can easily lead to serious accidents such as red coke falling to the ground, the coke stopper vehicle derailing, and damage to the furnace itself, with potentially severe consequences including the shutdown of the coking oven. Therefore, the operation of the three major vehicles in coke ovens urgently requires a interlocking control system for these vehicles, in order to prevent incorrect operations during their use and thus avoid accidents resulting from the lack of such interlocking that could lead to injuries or damage to personnel and equipment. However, due to the characteristics of the coke oven production process and various economic factors, the interlocked control of the three main equipment types in coke ovens is difficult to implement on a large scale. Thanks to the continuous efforts of the many professionals in the field of coking automation in our country, the chain control technology for the three types of vehicles used in coking plants has become increasingly mature, with a wide range of options available. Positioning technology and wireless communication technologies are employed in large coking plants in our country to enable communication between various mobile devices within these plants, thereby facilitating the chain control of these vehicles and the management of coking plant operations. However, due to high costs, such technologies are difficult to implement in smaller coking plants in our country. The Benxi Science and Technology Development Center has a large number of scientific and technical professionals, including senior engineers at the professorial level who have long been working in the coking industry; it has developed numerous achievements that have won awards for scientific and technological progress from Liaoning Province and Benxi City. Among them, the inter-chimney mobile equipment communication in the coke oven system is achieved using power line carrier technology for its interlocking control system. Thereby achieving interlocked control of the three main vehicles in the coke oven. This device boasts outstanding advantages such as low investment costs, reliable control, and easy maintenance. It has been operating stably on multiple coke ovens at the Coking Plants of Benxi Steel and Beigang Steel for many years, and is widely welcomed by coke plants in China, especially those of small and medium scale. I. System principle: The signal transmission between the three workshops of the system utilizes existing power lines and their conductors to transmit signals. The signal frequency ranges from 10 to 150 KHZ, which is quite different from the power frequency; moreover, the transmission frequency remains stable. The control cabinets installed in the three vehicles each contain transmitters, receivers, and logic control devices. A signal indicating that the coke stopper car is in position is sent manually; once the coke quenching car receives this signal and the coke stopper car is in place, it sends a signal to the coke pusher car indicating that it is ready to push the coke, and simultaneously releases the interlock on the coke pusher car. Completing a coke pushing process involves the use of carrier communication technology in the three-car interlock system, which enables signal transmission between the three cars and thus facilitates the interlock control of these cars in the coke oven. II. Main equipment and materials for the interlock system of the three major vehicles in coke ovens 1. For machine-type coke ovens: 1 pusher control cabinet ZZBK-00 per oven, 1 stopper control cabinet LZBK-00, 1 quenching control cabinet XJBK-00, 2 high-intensity anti-fog lights; 2 automatic switches, cables, and related materials. Furnace bank (2 coke ovens): Pusher control cabinet ZZBK-01: 2; Stopper control cabinet LZBK-01: 2; Coke quenching control cabinet XJBK-01: 1; High-intensity anti-fog lights: 4; Automatic switches, cables, and materials. 2. Clean coke oven: 1 coke pushing control cabinet ZZBK-00, 1 coke quenching control cabinet JXBK-00, 2 high-intensity anti-fog lights, automatic switches, cables, and materials. Blast furnace unit (2 coke ovens): Pusher control cabinet ZZBK-00, 2 units; Quenching control cabinet JXBK-00, 1 unit; High-intensity anti-fog lights, 4 units; Automatic switches, cables, and materials. III. External dimensions (in mm, length × width × height): Control cabinet for coke blocking vehicle: 500×400×850; Control cabinet for coke quenching vehicle: 500×600×850; Control cabinet for coke pushing vehicle: 500×600×850; Control cabinet for coke quenching and blocking: 500×600×850. IV. Main technical specifications: 1. Power supply: AC220V/380V ； 50HZ. 2. Appropriate impedance for line transmission: 5–600 ohms. 3. Signal frequency: 11KC–145KC. 4. Transmitting power: adjustable from 150 mV to 800 mV when the line impedance is 100 ohms. 5. Receiving sensitivity: adjustable from 20 mV to 800 mV. 6. Operating temperature range: -40 to 60 degrees Celsius. V. Main technical requirements: 1. The joints between the various rails of the power supply sliding wire must be reliably welded using metal with a cross-sectional area of more than 100 square millimeters. 2. When installing a variable-frequency speed control device on the heavy machinery, it is necessary to purify the power supply by adding reactors. (1) The ground resistance between the rails on which the three vehicles move is less than 10 ohms. (2) At least one of the rail gaps along the rails on which the three vehicles move is connected and welded with metal. (3) The 380V power supply lines for the three vehicles must indicate the phase sequence.