Main parameters of the inverter

1. Control method:

I.e., speed control, torque control, PID control or other means. After the control method is adopted, static or dynamic identification is generally performed according to the control precision.

2. Minimum operating frequency:

That is, the minimum speed of the motor running, when the motor is running at low speed, its heat dissipation performance is very poor, and the motor runs for a long time at low speed, which will cause the motor to burn out. At low speeds, the current in the cable also increases, which can also cause the cable to heat up.

3. Maximum operating frequency:

The general frequency of the inverter is up to 60Hz, and some even reach 400 Hz. The high frequency will make the motor run at high speed. For ordinary motors, the bearings can't run for a long time at the rated speed. Can the rotor of the motor withstand such a kind? Centrifugal force.

4. Carrier frequency:

The higher the carrier frequency setting, the higher the higher harmonic component, which is closely related to the length of the cable, the heating of the motor, and the heating of the cable heating inverter.

5. Motor parameters:

The inverter sets the power, current, voltage, speed and maximum frequency of the motor in the parameters. These parameters can be obtained directly from the motor nameplate.

6. Frequency hopping:

At a certain frequency point, resonance may occur, especially when the entire device is relatively high; when controlling the compressor, the surge point of the compressor should be avoided.

7. Acceleration and deceleration

The acceleration time is the time required for the output frequency to rise from 0 to the maximum frequency, and the deceleration time is the time required to fall from the maximum frequency to 0. The acceleration and deceleration time is usually determined by the frequency setting signal rising and falling. When the motor is accelerating, the rate of increase of the frequency setting must be limited to prevent overcurrent, and when decelerating, the rate of decrease is limited to prevent overvoltage.

Acceleration time setting requirement: Limit the acceleration current below the overcurrent capacity of the inverter, and do not cause the inverter to trip due to the over-speed. The deceleration time setting point is: prevent the smoothing circuit voltage from being too large, and the regenerative overvoltage stall is not caused. Let the frequency converter trip. The acceleration/deceleration time can be calculated according to the load. However, in the commissioning, the long acceleration/deceleration time is set according to the load and experience. The motor is observed by the start and stop motors to see if there is overcurrent or overvoltage alarm. Then the acceleration/deceleration setting time is gradually Shorten, the principle of no alarm occurs during operation, and repeat the operation several times to determine the optimal acceleration and deceleration time.

8. Torque boost

Called compensation torque, low speed to compensate for a motor stator winding resistance caused by the torque reduction, and the low-frequency range of f / V is increased method. When set to automatic, the voltage during acceleration can be automatically increased to compensate for the starting torque, so that the motor accelerates smoothly. If manual compensation is used, a better curve can be selected by experiment depending on the load characteristics, especially the starting characteristics of the load. For variable torque loads, if the selection is improper, the output voltage will be too high at low speed, and the phenomenon of wasting electric energy may even occur when the motor is loaded with load and the current is not high.

9. Electronic thermal overload protection

This function is set to protect the motor from overheating. It is the CPU inside the inverter that calculates the temperature rise of the motor based on the running current value and frequency, thus performing overheat protection. This function is only applicable to the “one-to-one” situation, and in the case of “one-to-one”, a thermal relay should be added to each motor.

Electronic thermal protection set value (%) = [motor rated current (A) / inverter rated output current (A)] × 100%.

10. Frequency limit

That is, the upper and lower limits of the inverter output frequency. The frequency limit is a protection function that prevents the device from malfunctioning or the external frequency setting signal source is faulty, causing the output frequency to be too high or too low to prevent damage to the device. In the application, it can be set according to the actual situation. This function can also be used for speed limit. If there are some belt conveyors, because the conveying material is not too much, in order to reduce the wear of the machine and the belt, the inverter can be driven and the upper limit frequency of the inverter is set to a certain frequency value. This allows the belt conveyor to operate at a fixed, low working speed.