VFD (Variable-frequency Drive) variable frequency motor no-load test run and load test run

VFD (Variable-frequency Drive) variable frequency motor no-load test run and load test run

1. Frequency conversion motor with load test run

Manually operate the running stop key on the VFD (Variable-frequency Drive) panel, observe the process of the variable frequency motor running and stopping and the display window of the VFD (Variable-frequency Drive) to see if there is any abnormality.

If the VFD (Variable-frequency Drive) exhibits an overcurrent protection action during the process of starting and stopping the motor, the acceleration and deceleration time should be reset. The acceleration of the motor during acceleration and deceleration depends on the acceleration torque, and the frequency change rate of VFD (Variable-frequency Drive) in the process of starting and braking is set by the user. When accelerating or decelerating at a fixed frequency change rate, the acceleration torque may be insufficient, resulting in motor stall, that is, the motor speed and VFD (Variable-frequency Drive) output frequency are not coordinated, resulting in over-current or over-voltage. Therefore, it is necessary to set the acceleration and deceleration time reasonably according to the moment of inertia of the motor and the load, so that the VFD (Variable-frequency Drive) frequency change rate can be coordinated with the motor speed change rate.

The way to check whether this setting is reasonable is to first select the acceleration and deceleration time according to experience. If over-current occurs during startup, the acceleration time can be extended appropriately; if over-current occurs during braking, then Appropriately extend the deceleration time. On the other hand, the acceleration and deceleration time should not be set too long, as it will affect the production efficiency, especially when starting and braking frequently.

If the VFD (Variable-frequency Drive) is still protected within the limited time, the running curve of start P stop should be changed from straight line to S-shaped, U-shaped line or S-shaped, reverse U-shaped line. When the load inertia of the motor is large, a longer start and stop time should be used, and the type of operation curve should be set according to its load characteristics.

If the VFD (Variable-frequency Drive) still has operating failures, try to increase the maintenance value of the maximum current, but the maintenance cannot be canceled, and at least 10% to 20% maintenance margin should be left. If the VFD (Variable-frequency Drive) fails to operate, it should be replaced with a VFD (Variable-frequency Drive) with a higher level of power.

2. No-load test run of frequency conversion motor

The variable-frequency motor runs without load. When setting the power and number of poles of the variable-frequency motor, the operating current of the VFD (Variable-frequency Drive) must be considered comprehensively.

Set the maximum output frequency, base frequency and torque characteristics of VFD (Variable-frequency Drive). General VFD (Variable-frequency Drive) has multiple VPf curves for users to choose, and users should choose the appropriate VPf curve according to the nature of the load when using it. For fan and pump loads, the torque operation code of VFD (Variable-frequency Drive) should be set to variable torque and reduced torque operation characteristics. In order to improve the low-speed performance of VFD (Variable-frequency Drive) startup, so that the output torque of the motor can meet the requirements of production load startup, the startup torque should be adjusted.

In the frequency conversion speed regulation system of asynchronous motor, the torque control is more complicated. In the low frequency band, the influence of resistance and leakage reactance cannot be ignored. If VPf is kept constant, the magnetic flux will decrease, thereby reducing the output torque of the motor. For this reason, the voltage should be properly compensated in the low frequency band to increase the torque. Generally, VFD (Variable-frequency Drive) is manually set by the user to make up.

Set the VFD (Variable-frequency Drive) to the built-in keyboard operation mode, press the run key and stop key, and observe whether the motor can start and stop normally.

Familiar with the maintenance code when the VFD (Variable-frequency Drive) fails, observe the factory value of the thermal maintenance relay, observe the setting value of the overload protection, and modify it if necessary. Users of VFD (Variable-frequency Drive) can set the electronic thermal relay function of VFD (Variable-frequency Drive) according to the instruction manual of VFD (Variable-frequency Drive). When the output current of VFD (Variable-frequency Drive) exceeds its allowable current, the overcurrent protection of VFD (Variable-frequency Drive) will cut off the output of VFD (Variable-frequency Drive). Therefore, the maximum threshold value of the VFD (Variable-frequency Drive) electronic thermal relay does not exceed the maximum allowable output current of the VFD (Variable-frequency Drive).