﻿ Determination of rated current of brushless motor_brushless motor and driver

# Determination of rated current of brushless motor

Author：奇沃无刷电机 Views：Close

2020-12-23 15:33

Rated current refers to the allowable current for long-term continuous operation of electrical equipment under rated environmental conditions (ambient temperature, sunshine, altitude, installation conditions, etc.).

Methods to determine the rated current of brushless motor:

1) . obtained from motor name plate or motor data book. (the motor should work under rated voltage)

2) When only the rated voltage and power of the motor can be obtained from the motor nameplate or motor data manual, the rated power can be divided by the rated voltage and then divided by the efficiency.

For 12V motor, the efficiency is usually 50% ~ 60%, we take 50%; for 24 V and higher rated voltage motor, the efficiency is usually 60% ~ 80%, we take 70%.

3) If we only know the rated voltage of the motor or the motor is working under non rated voltage, we can divide the locked rotor current of the motor by 3 as the rated current;

Or measure the internal resistance of the motor, divide the current obtained by dividing the working voltage by the internal resistance of the motor, and then divide it by 3 as the rated current (Note: when using the multimeter to measure the internal resistance of the motor, the indicated value of the internal resistance of the motor measured shall be subtracted from the indicated value of the internal resistance of the two probes of the multimeter which are directly short circuited).

Determination of motor starting current: the starting current of motor hard starting is about equal to motor locked rotor current. The locked rotor current is usually 3 ~ 5 times of the rated current. If the motor with rated current of 2a, the locked rotor current may be more than 6a, exceeding the maximum current that the motor can bear, then the motor hard start may burn the drive board