Cogging toque is a natural characteristic of some permanent magnet motor design which is less desirable characteristic for many applications. It’s also known as ‘detent’ or ‘no current’ torque.

Cogging torque is the torque needed to overcome the opposing torque created by the magnetic attractive force between magnets on the rotor and the iron teeth of the stator. There are multiple rotor positions within a revolution where the cogging torque is high.

Cogging torque creates vibration and noise during operation and acts to disturb the motor away from its desired position when used in servo applications. The cogging torque frequency is also closely correlated with the production of rotor losses both with and without current supplied to the armature.

The cogging torque frequency is given by the least common multiple (LCM) of the stator slots and the rotor poles.

4Q-CTS Vertical Version

Our 4Q Cogging Test System (CTS) is a stand-alone system to measure the detent torque of PM and PMSM motors. The detent torque is composed from Friction Torque and Cogging Torque. The 4Q-CTS perform the measurement while rotating the MUT (Motor Under Test) at a very low speed with very high accurate geared motor.


The test system can rotate in a constant accurate speed from 0.5-30rpm. The 4Q-CTS enables stable and highly reproducible measurements. It measures and provides;


  • Peak-to-Peak of cogging torque
  • Friction torque
  • Position repeatability tests – Display up to 10 measurements overlapping for comparison and investigation of same position
  • Cogging torque frequency – least common multiple (LCM) of the stator slots and the rotor poles.
Test Results of BLDC motor

General specification:


  • Speed range – 0.5 to 30 rpm
  • Angle – 0.09° (4000PPR)
  • Rotation – Both direction (CW & CCW)
  • Test results
    • Numeric value of Cogging / Friction
    • Display of Torque Vs. Angle
    • Hormonic analysis – 1-150 order
  • Ambient temperature – 0 to 50℃
  • Surrounding Humidity – 90%RH or below
  • Power input – 230VAC 50/60Hz

Connection interface – USB-B 2.0

Cogging vs. Angle


Model Number4Q-CTS-504Q-CTS-1004Q-CTS-2004Q-CTS-500
Rated Torque50 [mNm]100 [mNm]200 [mNm]500 [mNm]
Accuracy Scale0.1% F.S0.05% F.S


The system is scalable to test bigger or smaller motors by adding a torque measurement unit to the system with fast replacement within a minute.

Ordering No:4Q-CTS-___- 01
4Q-CTS-050:   50[mNm]
4Q-CTS-100: 100[mNm]
4Q-CTS-200: 200[mNm]
4Q-CTS-500: 500[mNm]
Example:4Q-CTS-200-01 mean cogging torque system with 200mNm range and vertical version.
For more details contact us