"OVERCURRENT" causes and treatments in the inverter - Solutions - Huaqiang

Photocoupler

First, external reasons:
1. The motor load is abrupt, causing excessive shock and overcurrent.
2. The insulation between the motor and the motor cable or the relative insulation of each other causes a short circuit between the turns or the ground, thus causing overcurrent.
3. The overcurrent fault is related to the leakage reactance of the motor and the coupling reactance of the motor cable, so the motor cable must be selected according to the requirements.
4. There is a power factor correction capacitor or surge absorbing device on the output side of the inverter.
5. When the speed encoder signal is lost or abnormal when it is equipped with the speed encoder, it will also cause overcurrent. Check the encoder for its cable 2 and the inverter itself:
1. Parameter setting problem:
For example, the acceleration time is too short, the ratio P of the PID regulator, the integral time I parameter is unreasonable, and the overshoot is too large, causing the inverter output current to oscillate.
2. Inverter hardware problem:
a) The current transformer is damaged. The phenomenon is that the main circuit of the inverter is powered. When the inverter is not started, there is current display and the current is changing. This can judge that the transformer is damaged.
b) The main circuit panel current and voltage detection channels are damaged, and overcurrent may also occur.
Board damage may be: 1) Due to poor environment, conductive solid particles adhere to the board, causing electrostatic damage. Or there is a corrosive gas that causes the circuit to corrode. 2) The zero potential of the board is connected with the casing. Due to the strong arc during the welding of the cabinet and the ground, the performance of the board will be affected. 3) Due to poor grounding, the zero volts of the board will be disturbed, which will also cause damage to the board.
c) Because the connection plug-in is not tight and not secure. For example, if the current or voltage feedback signal line is in poor contact, there may be a phenomenon that is sometimes absent when an overcurrent fault occurs.
d) When the load is unstable, it is recommended to use the DTC mode because the DTC control speed is very fast, generating a set of accurate torque and actual value of the flux every 25 microseconds, and then comparing the motor torque comparator with the magnetic flux. The output of the device optimizes the pulsation selector to determine the optimal switching position of the inverter, so that there is a use to suppress overcurrent. In addition, the speed loop adaptation (AUTOTUNE) will automatically adjust the PID parameters, so that the inverter output motor current is stable.