When the motor bearing begins to conduct electricity, the impedance of the bearing will determine the magnitude of the voltage. The impedance of the bearing is non-linear. It is related to the load, temperature, rotational speed of the motor bearing and the lubricating oil used. In all types of bearing currents, the switching frequency of the frequency converter will directly affect the failure rate of the motor. Increasing the modulation frequency of the frequency converter will accelerate the damage of the motor bearing within the limits of the bearing current that the bearing can withstand.

Solutions to reduce the insulation stress of the motor:

a) The output reactor can be used to limit the capacitive output current and reduce the voltage rise rate. In the output frequency of the inverter is less than 120Hz, iron core reactor can be used, and the inverter is the largest.

b) The modulation frequency is limited to 3 girls. Dry screw vacuum pump When the output frequency of the inverter is greater than 120Hz, a ferrite reactor can be used. The maximum modulation frequency of the inverter is limited to 6kHz.

c) Using the dy/dt filter, the voltage rise rate can be limited to below 5OO. This means that the capacitor charging current will be significantly reduced and the motor's spike voltage can be limited to 1.76 times the grid voltage.

d) The sine wave filter can make the output waveform of the inverter a perfect sine wave, which will reduce the stress on the motor insulation.

Ways to reduce the motor test motor bearing current:

a) Strengthen the insulation of the winding to improve the voltage insulation of the first gear motor.

b) Insulate the bearing to interrupt the circulation caused by the asymmetry of the magnetic path caused by the high frequency common mode voltage.

c) The motor shaft is grounded to suppress high frequency bearing current. The motor shaft ground can be installed separately or integrated into a rotary encoder.

d) Use elastic rubber or insulated serrated couplings, etc.