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When the VFD is not used, the leakage current is generally small. When using the VFD, because the power module of the inverter switches at high speed, there are high-order harmonics in the output current. Because of the inductance between the cable and the ground and between the cables, a large leakage current (up to 10 times when the VFD is not used) is generated.

When the motor is started, the starting current corresponding to the capacity will flow, and the transformer on the stator side of the motor will produce a voltage drop. When the motor capacity is large, the voltage drop will also have a great impact. The VFD connected to the same transformer will make a judgment of undervoltage or instantaneous stop, so sometimes the protection function acts, resulting in stop.

Ordinary motor can realize variable frequency speed regulation. However, it is not recommended to use it under low frequency (below 30Hz) for a long time to avoid the rise of motor temperature.

If the voltage is reduced completely in proportion when the frequency decreases, the ground torque at low speed tends to decrease because the AC impedance becomes smaller and the DC resistance remains unchanged. Therefore, given V / F at low frequency, the output voltage should be increased to obtain a certain starting torque. This compensation is called enhanced starting.

3% to 4%

The electrolytic capacitor needs to be replaced after 30,000-40,000 hours of use.

In this case, first check whether the cooling fan operates normally by hand. When the fan operates normally, please check whether the ambient temperature is too high, whether the ventilation of the VFD is poor, or whether the temperature detection circuit is damaged.

SPI is an input phase loss detection fault.
1. When the input phase loss protection is enable, the input power supply is in phase loss
2. When the input phase loss protection is enable, the input phase loss detection circuit fails.
3. Check whether the power input is normal (phase loss or three-phase imbalance)

1. Check whether the input cable voltage is too low or the power supply voltage fluctuates too much. If so, adjust the grid voltage to the normal range.
2. Check whether the DC bus voltage displayed on the keypad is normal (1.35 times of the input voltage), and check whether the factory voltage level setting is correct. If it is not a standard voltage, adjust it to an appropriate voltage.
3. If the power is above 37kW, check whether the fan is normal. If the fan is stuck or burnt out, the contactor will not close and report UV.