【Daily Question 20090315】Parameter Setting of Inverters (IX)?

It should be fine, I guess. Move a sofa over and wait; Reply: lol, it’s time to go to bed. . What kind of look is that? . Only after answering did I see the two characters \"Over\": [This post was last edited by ZJYSSF on 2009-3-15 00:50]

It’s fine under light load

It probably won’t work, because operating at high frequency for a long time could have a significant impact on the motor:lol

1 Selection of the V/f type: The selection of the V/f type includes parameters such as the maximum frequency, fundamental frequency, and torque type. The maximum frequency is the highest frequency at which the inverter-motor system can operate. Since the maximum frequency of the inverter itself can be high, when the maximum frequency allowed by the motor is lower than that of the inverter, the settings should be made according to the requirements of the motor and its load. The fundamental frequency serves as the boundary between constant power control and constant torque control of the motor by the inverter, and it should be set according to the motor’s rated voltage. Torque type refers to whether the load is a constant torque load or a variable torque load. The user selects one of the types based on the V/f type chart in the frequency converter’s instruction manual and the characteristics of the load. Based on the actual conditions and requirements of the motor, we set the maximum frequency at 83.4 Hz, and the basic frequency at the power frequency of 50 Hz. Load type: Below 50Hz it is a constant torque load, and between 50–83.4Hz it is a constant power load. 2 How to adjust the starting torque: Adjusting the starting torque is intended to improve the low-speed performance of the inverter during startup, so that the torque output by the motor can meet the requirements for starting up production processes. In the variable-frequency speed control system of asynchronous motors, torque control is relatively complex. In the low-frequency range, the effects of resistance and leakage reactance cannot be ignored; if V/f is kept constant, the flux will decrease, which in turn reduces the motor’s output torque. To this end, the voltage must be appropriately compensated in the low-frequency range to increase torque. However, the effect of leakage impedance depends not only on frequency but also on the magnitude of the motor current, making accurate compensation difficult. In recent years, some frequency converters capable of self-compensation have been developed abroad, but they require extensive calculations and involve complex hardware and software; as a result, ordinary frequency converters are usually adjusted for compensation manually by the user. For the frequency converter we use, it is appropriate to set the torque increase range between 1% and 5%. 3 How to set the acceleration and deceleration times. The operating equation for the motor: Where Tt is the electromagnetic torque ； T1 represents the load torque. The motor acceleration dw/dt depends on the acceleration torque (Tt, T1), while the rate of frequency change of the inverter during startup and braking is set by the user. When the motor’s moment of inertia J and the motor load change at a pre-set frequency rate, either accelerating or decelerating, it is possible that the acceleration torque may be insufficient, leading to motor stall. This occurs when the motor’s speed does not match the output frequency of the inverter, resulting in overcurrent or overvoltage. Therefore, it is necessary to set the acceleration and deceleration times appropriately based on the motor’s moment of inertia and the load, so that the frequency change rate of the inverter can be coordinated with the motor’s speed change rate. A way to check whether this setting is reasonable is to select the acceleration and deceleration time values based on experience. If overcurrent occurs during startup, the acceleration time can be appropriately extended ； If overcurrent occurs during braking, appropriately extend the deceleration time ； On the other hand, the acceleration and deceleration times should not be set too long, as excessive time will affect production efficiency, especially during frequent starts and stops. We set the acceleration time to 15s and the deceleration time to 5s. 4 Frequency skipping V/f control of inverters driving asynchronous motors in certain frequency ranges. The current and speed of the motor experience fluctuations; in severe cases, the system fails to operate. Overcurrent protection can even prevent the motor from starting properly during acceleration, and this problem is more pronounced when the motor is under light load or rotating at low speeds. Therefore, all variable frequency drives are equipped with a frequency skipping function, allowing users to set the skipping points and the width of these points on the V/f curve based on the frequency at which oscillations occur in the system. When the motor accelerates, it can automatically skip these frequency ranges to ensure the normal operation of the system. 5 Overload rate setting: This setting is used for overload protection of the inverter and motor. When the output current of the inverter exceeds the OL setting value determined by the overload rate setting and the motor’s rated current, the inverter provides overload protection (OL) based on a inverse-time characteristic; when overload protection is activated, the inverter stops delivering power. 6 Input of motor parameters: Among the parameter input options for the frequency converter, there are those related to the basic parameters of the motor, such as its power, rated voltage, rated current, rated speed, number of poles, etc. The input of these parameters is very important, as it directly affects the proper functioning of certain protection functions in the inverter. It is essential to enter the values correctly based on the actual parameters of the motor, in order to ensure the proper operation of the inverter.

According to the speed control formula for variable frequency, n=60F/P, it can be seen that the higher the frequency, the faster the motor speed. It should be fine for a short period of time; for longer durations, it’s better to choose one with a larger power margin.

It’s fine under light loads and for short periods of time, but it probably won’t work for long durations

It depends on the load of the motor, because the higher the frequency, the faster the motor speeds up. If it operates at high speed under overload for a long time, it will damage the motor.

It shouldn’t work; the normal operating frequency for such designs is 50 Hz. Therefore, many of the design parameters for motors are based on a frequency of 50 Hz. If the motor operates at a frequency higher than 50 Hz for an extended period, it’s possible that components such as the bearings could overheat and damage the motor. If you want to operate above 50 Hz, you can use this variable-frequency motor.