What are the requirements for inverter without load?

The technical requirements of inverter with motor no-load operation need to consider the working current of the inverter, set the maximum output frequency of the inverter, base frequency, set the torque characteristics and set the inverter to its own keyboard operation mode and so on.

Frequency converter with motor no-load running technical requirements

1、When setting the power and pole number of the motor, the working current of the frequency converter should be considered comprehensively.

2、Set the maximum output frequency, base frequency and set the torque characteristics of the frequency converter.

The selection of V/f type includes items such as maximum frequency, base frequency and torque type.

The maximum frequency is the highest frequency at which the inverter-motor system can run.Since the maximum frequency of the inverter itself may be higher, when the maximum frequency allowed for the motor is lower than the maximum frequency of the inverter, it should be set according to the requirements of the motor and its load.

The basic frequency is the dividing line between constant power control and constant torque control of the motor by the frequency converte and should be set according to the rated voltage of the motor.

The torque type refers to whether the load is constant torque load or variable torque load.

Users choose one of these types according to the V/f type diagram in the instruction manual of the inverter and the load characteristics.

 General-purpose inverters are equipped with several V/f curves for users to choose, users should choose the appropriate V/f curve according to the nature of the load.

In case of fan and pump loads, the torque operation code of the inverter should be set to variable torque and reduced torque operation characteristics.

In order to improve the low-speed performance of the frequency converter at startup, so that the motor output torque can meet the requirements of production load startup, the starting torque should be adjusted.

In the asynchronous motor frequency control system, the torque control is more complicated.

In the low-frequency band, due to the influence of resistance, leakage reactance can not be ignored, if still maintain V / f as a constant, the magnetic flux will be reduced, which in turn reduces the output torque of the motor.

For this reason, in the low-frequency band, the voltage should be properly compensated to enhance the torque. General inverter are manually set by the user to compensate. Hitachi J300 inverter provides users with two options: self-setting and automatic torque increase.

3、Set the inverter to the keyboard operation mode, press the run key and stop key, and observe whether the motor can start and stop normally.

4、Familiarize  with the protection code when the frequency converter runs into trouble, observe the factory value of the thermal protection relay, observe the setting value of the overload protection, and modify it when needed.

The user of the frequency converter can set the electronic thermal relay function of the frequency converter according to the instruction manual of the frequency converter.

The threshold value of the electronic thermal relay is defined as the ratio of the rated currents of both the motor and the inverter, usually expressed as a percentage.

When the output current of the inverter exceeds its allowable current, the overcurrent protection of the inverter will cut off the output of the inverter.

Therefore, the maximum value of the threshold of the inverter electronic thermal relay does not exceed the maximum allowable output current of the inverter.