By setting these 16 inverter parameters, 90% of the inverter debugging was completed successfully

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Inverter models have numerous setting parameters, each of which has a specific range of values. In practice, it is common for the inverter to fail to operate properly due to improper settings of certain parameters. Therefore, inverter tuning begins with correctly setting the inverter parameters. Changhui Instruments has summarized 16 basic methods for setting frequency converter parameters, to help everyone refer to them when making the correct settings. 1. Control method, namely speed control, torque control, PID control, or other methods. After adopting a control method, static or dynamic identification is generally required based on the control accuracy. 2. Minimum operating frequency refers to the lowest speed at which the motor can operate. When the motor runs at low speeds, its heat dissipation performance is poor, and operating it at such low speeds for an extended period can lead to motor damage. Moreover, at low speeds, the current in the cable also increases, which can cause the cable to heat up. 3. Maximum operating frequency: The maximum frequency of ordinary frequency converters is up to 60Hz, with some even reaching 400Hz. A high frequency enables the motor to operate at high speeds; for conventional motors, their bearings cannot sustain operation at speeds exceeding their rated values for long periods, and it is also uncertain whether the motor’s rotor can withstand such centrifugal forces. 4. Carrier frequency: The higher the carrier frequency set, the greater the higher harmonic components, which is closely related to factors such as cable length, motor heating, cable heating, and inverter heating. 5. Motor parameters: The frequency converter allows for setting the motor’s power, current, voltage, speed, and maximum frequency in its parameters; these values can be obtained directly from the motor’s nameplate. 6. Frequency hopping: At a certain frequency point, resonance may occur, especially when the overall level of the device is high ； When controlling the compressor, it is necessary to avoid its surge point. 7. Acceleration and deceleration time: The acceleration time is the time required for the output frequency to rise from 0 to the maximum frequency, while the deceleration time is the time required for it to drop from the maximum frequency back to 0. Generally, the rise and fall of the frequency set signal are used to determine the acceleration and deceleration times. When the motor accelerates, the rate of increase in frequency setting must be limited to prevent overcurrent; during deceleration, the rate of decrease must be limited to prevent overvoltage. Acceleration time setting requirement: Limit the acceleration current below the inverter’s overcurrent capacity, so as to prevent overcurrent from causing the inverter to trip ； The key point in setting the deceleration time is to prevent the voltage in the smoothing circuit from becoming too high, thereby avoiding stall due to regenerative overvoltage and causing the inverter to trip. The acceleration and deceleration times can be calculated based on the load, but during debugging, longer acceleration and deceleration times are often set initially based on both the load and experience, with the operation of the motor during start-up and shutdown used to check for any overcurrent or overvoltage alarms ； Then, gradually shorten the acceleration and deceleration setting times; by repeating this process several times while ensuring that no alarms occur during operation, the optimal acceleration and deceleration times can be determined. 8. Torque enhancement, also known as torque compensation, is a method of increasing the f/V ratio in the low-frequency range in order to compensate for the reduction in torque at low speeds caused by the resistance of the motor stator windings. When set to automatic, the voltage during acceleration can be increased automatically to compensate for the starting torque, ensuring smooth motor acceleration. When manual compensation is used, a suitable curve can be selected through testing based on the load characteristics, especially the starting characteristics of the load. For variable-torque loads, improper selection can result in excessively high output voltage at low speeds, leading to energy waste; it may also cause high current when the motor starts under load, preventing an increase in speed. 9. Electronic thermal overload protection: This function is designed to protect the motor from overheating. It works by having the CPU in the inverter calculate the temperature rise of the motor based on the operating current and frequency, thereby providing overload protection. This function is only applicable to the “1-to-1” configuration; in a “1-to-many” setup, thermal relays must be installed on each motor. Electronic thermal protection setting value (%) = ×100%. 10. Frequency limit: the upper and lower limits of the output frequency of the inverter. Frequency limitation is a protective feature designed to prevent the output frequency from becoming too high or too low due to accidental operations or failures in external frequency setting signal sources, thereby avoiding damage to the equipment. Set it according to the actual situation in the application. This function can also be used for speed limitation. In some belt conveyors, where the amount of material being transported is not large, in order to reduce wear on the machinery and the belt, an inverter can be used for drive, with the upper frequency limit of the inverter set to a specific value. This allows the belt conveyor to operate at a fixed, lower speed. 11. Bias frequency, also known as deviation frequency or frequency bias setting. Its purpose is to allow adjustment of the output frequency at the lowest level of the frequency setting signal, when the frequency is set by an external analog signal (voltage or current). In some inverters, when the frequency setting signal is set to 0%, the deviation value can range from 0 to fmax; some inverters (such as Meidenisho and Sanken) also allow for the setting of the bias polarity. If, during debugging, the frequency setting signal is set to 0%, the output frequency of the inverter is not 0Hz but rather xHz; in this case, setting the bias frequency to negative xHz will enable the inverter’s output frequency to be 0Hz. 12. Frequency setting signal gain: This function is effective only when the frequency is set using an external analog signal. It is used to address the discrepancy between the externally set signal voltage and the voltage inside the inverter (+10V) ； It also facilitates the selection of the signal voltage for simulation. During setting, when the analog input signal is at its maximum value (such as 10V, 5V, or 20mA), the frequency percentage that can be output in the f/V graph is determined, and this value is used as a parameter for setting ； If the external control signal is 0-5V and the inverter’s output frequency ranges from 0-50Hz, then setting the gain signal to 200% will suffice. 13. Torque limitation can be of two types: drive torque limitation and braking torque limitation. It calculates torque based on the voltage and current values output by the inverter, using a CPU; this enables significant improvement in the load recovery characteristics during acceleration, deceleration, and constant-speed operation. The torque limitation function enables automatic acceleration and deceleration control. It is assumed that when the acceleration and deceleration time is less than the load inertia time, the motor can still accelerate and decelerate automatically according to the set torque value. The drive torque function provides high starting torque; during steady-state operation, it controls the motor slip to keep the motor torque within the maximum set value. Even if the load torque suddenly increases or if the acceleration time is set too short, this will not cause the inverter to trip. When the acceleration time is set too short, the motor torque will not exceed the maximum set value either. A high driving torque is beneficial for starting, and it is appropriate to set it at 80~100%. The lower the set value of the braking torque, the greater the braking force, which is suitable for situations requiring rapid acceleration and deceleration. If the set value of the braking torque is too high, an overpressure alarm will occur. If the braking torque is set to 0%, the total amount of energy regenerated and supplied to the main capacitor can be brought close to 0, allowing the motor to slow down to a stop without using brake resistors, thereby preventing tripping. However, with certain loads, such as when the braking torque is set to 0%, brief idling occurs during deceleration, which causes the inverter to start repeatedly and results in significant fluctuations in current; in severe cases, this can lead to the inverter tripping, so this phenomenon should be taken into consideration. 14. Acceleration and deceleration mode selection, also known as acceleration and deceleration curve selection. Generally, frequency converters have three types of curves: linear, nonlinear, and S-shaped; usually, the linear curve is the most commonly chosen ； Nonlinear curves are suitable for variable torque loads, such as fans ； The S-curve is suitable for constant torque loads, where the acceleration and deceleration changes are relatively slow. During setup, the appropriate curve can be selected based on the characteristics of the load torque; however, there are exceptions. When debugging the inverter for a boiler exhaust fan, I initially chose a nonlinear acceleration and deceleration curve, and as soon as the fan started operating, the inverter tripped. Numerous parameter adjustments proved ineffective, but once a S-curve was used, everything worked properly. The reason for this is that before startup, the induced draft fan rotates on its own due to the flow of smoke in the flue, and it rotates in the reverse direction, acting as a negative load. Therefore, an S-curve is used to slow down the increase in frequency at the moment of startup, thereby preventing the inverter from tripping. Of course, this is a method applied to inverters that do not have a DC braking function for startup. 15. Torque vector control: Vector control is based on the theoretical assumption that asynchronous motors and DC motors have the same mechanism for generating torque. The vector control method involves breaking the stator current down into a magnetic field current and a torque current, controlling each of them separately, and then outputting the combined stator current to the motor. Therefore, in principle, the same control performance as that of a DC motor can be achieved. By utilizing the torque vector control function, the motor can deliver maximum torque under various operating conditions, especially in the low-speed operation range. Most modern frequency converters use feedback-free vector control. Since they can compensate for slip based on the magnitude and phase of the load current, the motors thus exhibit very stiff mechanical properties, which is sufficient for most applications; there is no need to install a speed feedback circuit outside the frequency converter. For the setting of this function, you can choose either valid or invalid based on the actual situation. The function related to this is slip compensation control, which serves to compensate for the speed deviation caused by load fluctuations by adding a slip frequency corresponding to the load current. This function is mainly used for positioning control. 16. Energy-saving control: Fans and water pumps are both types of torque-reducing loads, meaning that as the speed decreases, the load torque decreases in proportion to the square of the speed. Inverters with energy-saving control functions come equipped with a dedicated V/f mode, which improves the efficiency of both the motor and the inverter. This mode allows the inverter to automatically reduce its output voltage based on the load current, thereby achieving energy savings. It can be enabled or disabled depending on the specific circumstances. It should be noted that the electronic thermal overload protection and frequency limitation are quite advanced features; however, some users are unable to activate these features during equipment upgrades – the inverter trips frequently when they are activated, while everything works normally when they are disabled. The reasons are as follows: ① The parameters of the original motor differ significantly from those required for a motor to be used with an inverter. ②There is insufficient understanding of the parameter setting functions; for example, the energy-saving control function can only be used in the V/f control mode and not in the vector control mode. ③Vector control mode is enabled, but no manual setting or automatic reading of motor parameters was performed, or the reading method was incorrect. Source: Changhui Instruments http://yunrun.com.cn/