I am using a hub motor around 800W and want to measure the resistance of the motor, but do not have the milli ohm meter and also want to understand if the below technique can work. It is 60V motor so my idea is to give 48V with current limit using DC power supply and manually hold the rotor to avoid back emf to U phase, V and W phases will be grounded, then the DC supply will display the current drawn by the motor. From that calculate the resistance using ohm's law. Due to inductance the current may raise slowly, once the current is stable i will do the measurement. Is it correct method and will it be accurate?
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\$\begingroup\$ Folks often want to characterize a motor. This can be done via measuring voltage, current, speed, and torque (and sometimes a temperature) under various conditions - varying the load torque and supplied voltage is pretty common. \$\endgroup\$Abel– Abel2025-09-30 18:14:09 +00:00Commented Sep 30 at 18:14
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[...] the DC supply will display the current drawn by the motor. From that calculate the resistance using ohm's law. Due to inductance the current may raise slowly, once the current is stable i will do the measurement. Is it correct method and will it be accurate?
This is a two-terminal resistance measurement whose accuracy is degraded by contact resistance and by the resistance of wires going back to the DC supply.
When winding resistance is less than a few ohms, you really want to try for a Kelvin-type (4-terminal) measurement. This will separate the current path from the voltage-measuring path. It requires a current source, and a separate voltage-measuring meter...many multimeters have sufficient voltage scale ranges to give you accuracy:
simulate this circuit – Schematic created using CircuitLab
Do be careful to clamp that motor shaft. And do be careful to turn up current slowly, and back down slowly...don't use its on-off switch.
