Basic methods and steps of VFD (Variable-frequency Drive) debugging

Basic methods and steps for VFD (Variable-frequency Drive) debugging:

1. No-load power-on test of VFD (Variable-frequency Drive)

1 Ground the ground terminal of the VFD (Variable-frequency Drive).

2 Connect the power input terminal of the VFD (Variable-frequency Drive) to the power supply through the leakage protection switch.

3 Check whether the VFD (Variable-frequency Drive) display window is normal at the factory. If it is not correct, it should be reset, otherwise it is required to return.

4. Be familiar with the operation keys of VFD (Variable-frequency Drive). A general VFD (Variable-frequency Drive) has 6 keys such as run (RUN), stop (STOP), program (PROG), data P confirmation (DATAPENTER), increase (UP, ▲), decrease (DOWN, ") and so on. , The definition of different VFD (Variable-frequency Drive) operation keys is basically the same. In addition, some VFDs (Variable-frequency Drive) also have monitoring (MONITORPDISPLAY), reset (RESET), jog (JOG), shift (SHIFT), etc. function keys.

2. VFD (Variable-frequency Drive) with motor no-load operation

1. To set the power and number of poles of the motor, the working current of the VFD (Variable-frequency Drive) should be comprehensively considered.

2. Set the maximum output frequency, fundamental frequency and torque characteristics of the VFD (Variable-frequency Drive). Universal VFD (Variable-frequency Drive) is equipped with multiple VPf curves for users to choose, and users should choose the appropriate VPf curve according to the nature of the load. For fan and pump loads, set the torque operation code of VFD (Variable-frequency Drive) to variable torque and reduced torque operation characteristics. In order to improve the low-speed performance when VFD (Variable-frequency Drive) starts, so that the torque output by the motor can meet the requirements of starting the production load, the starting torque should be adjusted. In the variable frequency speed regulation system of asynchronous motor, the control of torque is more complicated. In the low frequency band, since the influence of resistance and leakage reactance cannot be ignored, if VPf is still 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 and compensated by the user.

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

4. Familiar with the protection code of VFD (Variable-frequency Drive) operation failure, observe the factory value of thermal protection relay, observe the set value of overload protection, and modify it if necessary. The user 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 the VFD (Variable-frequency Drive) exceeds its allowable current, the overcurrent protection of the VFD (Variable-frequency Drive) will cut off the output of the 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).

3. Trial operation with load

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

2. If the VFD (Variable-frequency Drive) has overcurrent protection action during the process of starting P and stopping the motor, the acceleration P 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 the VFD (Variable-frequency Drive) in the process of starting and braking is set by the user. If the moment of inertia of the motor or the load of the motor changes, when the acceleration or deceleration is carried out according to the preset frequency change rate, there may be insufficient acceleration torque, which will cause the motor to stall, that is, the motor speed and the VFD (Variable-frequency Drive) output frequency. coordination, resulting in overcurrent or overvoltage. 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 frequency change rate of the VFD (Variable-frequency Drive) can be coordinated with the speed change rate of the motor.

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

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

4. If the VFD (Variable-frequency Drive) still has operating failure, try to increase the protection value of the maximum current, but the protection cannot be cancelled, and at least 10% to 20% of the protection margin should be reserved.

5. If the VFD (Variable-frequency Drive) operation failure still occurs, the inverter with a higher power level should be replaced.

6. If the VFD (Variable-frequency Drive) drives the motor to fail to reach the preset speed during startup, there may be two situations:

(1) Electromechanical resonance occurs in the system, which can be judged from the sound of the motor running.

By setting the frequency jump value, the resonance point can be avoided. General VFD (Variable-frequency Drive) can set three jump points. When a VFD (Variable-frequency Drive) controlled by VPf drives an asynchronous motor, the current and speed of the motor will oscillate in certain frequency ranges. In severe cases, the system cannot run, and even overcurrent protection occurs during the acceleration process, making the motor unable to start normally. , more serious when the motor is lightly loaded or the moment of inertia is small. Common VFDs (Variable-frequency Drive) are equipped with frequency jumping function. Users can set jumping point and jumping width on the VPf curve according to the frequency point where the system oscillates. When the motor accelerates, these frequency segments can be automatically skipped to ensure the normal operation of the system.

(2) The torque output capacity of the motor is not enough. Different brands of VFD (Variable-frequency Drive) have different factory parameter settings. Under the same conditions, the load capacity is different, and it may also be due to different VFD (Variable-frequency Drive) control methods. , resulting in different load carrying capacity of the motor; or due to different output efficiency of the system, resulting in different load carrying capacity. In this case, the value of the torque boost amount can be increased. If it cannot be reached, the manual torque boost function can be used, do not set too large, the temperature rise of the motor will increase at this time. If it still doesn't work, a new control method should be used. For example, Hitachi VFD (Variable-frequency Drive) adopts the method of constant VPf ratio. Torque output capability. For fan and pump loads, the torque reduction curve value should be reduced.

4. Debugging of VFD (Variable-frequency Drive) and the host computer

VFD (Variable-frequency Drive) is connected to the host computer for system debugging. After the manual basic setting is completed, if the system has