The inverter has single phase 220V and three-phase 380V, and the input phase loss is only in the three-phase product. The diagram shows the main circuit of the inverter, R, S, and T are the three-phase AC input, and when one of the phases is disconnected due to the failure of the fuse or breaker, the phase loss fault occurs.
1) Check whether the motor is overheat
If the temperature rise of the motor is not high, the electronic thermal protection function of the inverter should be checked first. If the inverter still has surplus capacity, increase the preset value of the electronic thermal protection function. If the temperature rise of the motor is too high, and the overload appears to be normal overload, the overload of the motor is explained. At this point, the transmission ratio should be properly increased to reduce the load on the motor shaft, increase the transmission ratio if possible. If the transmission ratio cannot be increased, the capacity of the motor should be increased.
2) Check the three phase voltage balance on motor side
If the three-phase voltage on the motor side is unbalanced, the three-phase voltage of the output end of the inverter should be checked again. If it is not balanced, the problem is in the inverter. If the inverter output voltage is balanced, the problem lies in the line between the inverter to motor, we should check all the terminal screws are tightened, if there are other electrical contactor or appliances between the inverter and the motor, check whether the connection terminals have been tightened, and the contact condition of contact is good.
In the operation of the motor, the running current exceeds the rated value, but less than the over-current limit value, the operation time is longer, such phenomenon is called overload. The basic characteristics are: Although the current overload exceeds the rated value, but the exceeding range is small, generally do not form a large surge current (otherwise it becomes overcurrent fault), another prominent feature is the overload is accumulated, and the overload fault will be reported only the accumulation time is reached.
1) Mechanical overload
The main features is that the motor is heated up which can be sensed by hand touching; or read the running current from the inverter screen, and compare it with the rated current to judge the overload situation.
2) Unbalanced three-phase voltage
Overload trip occur due to running current of a certain phase is too large, its features is that motor heating is uneven which cannot be found by reading the running current (as many inverter display displays one phase current only); the effective method is to use the voltage meter to measure the three-phase output voltage of the inverter, thus determining whether there is phase loss or imbalance voltage.
The current detection part of the inverter breaks down, and the detection of the current signal is too large, leading to overload trip
The current detection part of the inverter has a fault, and the detected current signal is too large, resulting in overload trip