It is believed that many power practitioners are familiar with the inverter. Compared with the traditional electrical circuit control, the inverter has a high technology content, which is a combination of strong and weak current equipment. Therefore, its faults are various, so we can only summarize the experience continuously from practice combined with theoretical knowledge. Here are 15 common problems about the inverter (definition and part of frequency conversion terms Frequent failures), do you know all these?

1. What is the frequency conversion resolution? What's the significance?

For the frequency converter with digital control, even if the frequency command is an analog signal, the output frequency is also given in stages. The smallest unit of this difference is called the frequency conversion resolution. The frequency conversion resolution is usually 0.015 ~ 0.5Hz. For example, if the resolution is 0.5Hz, then the upper part of 23Hz can be changed to 23.5 and 24.0hz, so the motor action is also followed step by step. This creates problems for uses like continuous coiling control. In this case, if the resolution is about 0.015hz, it can also fully adapt to a level difference of less than 1R / min for a 4-stage motor. In addition, the given resolution of some models is different from the output resolution.

2. What's the significance of having models with acceleration time and deceleration time that can be given respectively, and models with acceleration and deceleration time that can be given together?

Acceleration and deceleration can be given separately, which is suitable for short-time acceleration and slow deceleration, or for small machine tools which need to strictly give the production time, but for fan drive and other occasions, the acceleration and deceleration time are longer, and the acceleration time and deceleration time can be given together.

3. What is regenerative braking?

If the motor reduces the command frequency during operation, the motor will change to asynchronous generator state and operate as a brake, which is called regenerative (Electrical) brake.

4. Can we get more braking force?

The regenerative energy from the motor is stored in the filter capacitor of the inverter. Due to the relationship between the capacity of the capacitor and the withstand voltage, the regenerative braking force of the general inverter is about 10% ~ 20% of the rated torque. If the optional brake unit is used, it can reach 50% ~ 100%.

5. Protection function of frequency converter?

The protection functions can be divided into the following two categories:

(1) After the abnormal state is detected, the corrective action will be carried out automatically, such as over-current stall prevention and regeneration over-voltage stall prevention.

(2) After detecting the abnormality, the PWM control signal of power semiconductor device is blocked to make the motor stop automatically. Such as over-current cut-off, regeneration over-voltage cut-off, semiconductor cooling fan overheating and instantaneous power failure protection.

6. Why does the protection function of the frequency converter act when the clutch is used for continuous load?

When the clutch is used to connect the load, at the moment of connection, the motor changes rapidly from the no-load state to the area with large slip rate, and the large current flowing through causes the over-current trip of the frequency converter, which can not operate.

7. In the same factory, when large motors move together, the frequency converter stops during operation. Why?

When the motor starts, it will flow through the starting current corresponding to the capacity, and the transformer at the stator side of the motor will generate voltage drop. When the motor capacity is large, the voltage drop will also have a large impact. The frequency converter connected to the same transformer will make a judgment of undervoltage or instantaneous stop, so sometimes the protection function (IPE) acts, resulting in the stop of operation.

8. What does stall prevention mean?

If the given acceleration time is too short, the output frequency of the frequency converter changes much more than the speed (electrical angle frequency), the frequency converter will trip due to the overcurrent, and the operation will stop, which is called stall. In order to prevent the motor from stalling, it is necessary to detect the current and control the frequency. When the accelerating current is too large, slow down the accelerating speed properly. This is also true when slowing down. The combination of the two is the stall function.

9. Is there any restriction on installation direction when installing frequency converter?

The internal and back structure of the frequency converter considers the cooling effect, and the relationship between the top and the bottom is also important for ventilation. Therefore, for the unit type in the panel and hanging on the wall, take the longitudinal position, and install it vertically as much as possible.

10. Inverter over voltage

The over-voltage alarm usually occurs when the machine is stopped. The main reason is that the deceleration time is too short or the braking resistance and braking unit have problems.

11. Converter temperature too high

In addition, the frequency converter has over temperature fault. In case of over temperature alarm, if the temperature sensor is normal after inspection, it may be caused by interference. The fault can be shielded. In addition, the fan and ventilation condition of the frequency converter should be checked. For other types of faults, it is better to contact the manufacturer to get a quick and feasible solution.

12. Over current is the most frequent phenomenon of frequency converter alarm

Over current phenomenon of frequency converter

(1) When it is restarted, it will trip as soon as the speed is increased. This is a very serious phenomenon of overcurrent. The main reasons are: load short circuit, mechanical part stuck; inverter module damaged; motor torque is too small and so on.

(2) When the power is on, it will jump. This phenomenon can not be reset. The main reasons are: the module is bad, the drive circuit is bad, and the current detection circuit is bad. When restarting, it does not trip immediately, but when accelerating, the main reasons are: the acceleration time setting is too short, the current upper limit setting is too small, and the torque compensation (V / F) setting is high.

13. Can the motor be directly put into a fixed frequency converter without soft starting?

It is possible at very low frequency, but if the given frequency is high, it is similar to the condition of direct starting of power frequency power supply. Large starting current (6~7 times of rated current) will flow, and the motor cannot be started because the converter cuts off the over-current.

14. What should be paid attention to when the motor operates over 60Hz?

Pay attention to the following items when operating over 60Hz

(1) The operation of machinery and devices at this speed shall be possible (mechanical strength, noise, vibration, etc.)

(2) When the motor enters the constant power output range, its output torque shall be able to maintain operation (the output power of fan, pump and other shafts increases in proportion to the cubic of speed, so attention shall also be paid when the speed is slightly increased).

(3) The problem of bearing life should be fully considered.

15. What happens if the frequency converter is not used for a long time?

1. The bearing lubricating fluid of frequency converter fan is dry, which affects the use.

2. High voltage filter capacitor is not easy to bulge for a long time, and low voltage electrolytic capacitor is easy to leak liquid.