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AKD – How to Determine Number of Motor Poles

Configuring an unknown motor, it might be necessary to determine the number of motor poles, if this is not given.

This analyze can easily be done within the AKD Workbench.

The following steps need to be done:

  1. Disable the drive: DRV.DIS
  2. Set drive into service mode and into torque mode: DRV.CMDSOURCE 0 and DRV.OPMODE 0
  3. Set motor poles to zero and motor phase to zero: MOTOR.POLES 0 and MOTOR.PHASE 0
  4. Enable the drive: DRV.EN
  5. Apply a torque to the motor: IL.CMDU X -> X needs to be set depending on your motor
  6. Afterwards increase the motor phase in 30 degrees steps and after each step read the actual position:
    1. MOTOR.PHASE 0 and  PL.FB
    2. MOTOR.PHASE 30 and  PL.FB
    3. MOTOR.PHASE 60 and  PL.FB
    4. MOTOR.PHASE 90 and  PL.FB……..
    5. …..
    6. MOTOR.PHASE 359 and  PL.FB
    7. MOTOR.PHASE 30 and  PL.FB 4455
  7. Disable the drive again and reset motor phase: DRV.DIS and MOTOR.PHASE 0

Due to the fact that you increased the motor phase in 30 degrees steps your motor provided one electrical revolution -> movement about one pole pair.

This means by taking the position delta of the first 30 degree measurement and the last 30 degree measurement will show you the movement for one revolution.

Based on this information you can now calculate the number of motor poles. Your base information is given from the unit screen, where you can get the position change for one rotation of your feedback device.  (e.g. UNIT.PROTARY 4 -> this means you are getting 16 bit per revolution)

Now you just need to devide the position information you expect for one revolution of your feedback device by the position delta and thus you are getting the number of motor pole pairs for your motor.

Example:

DRV.DIS

DRV.CMDSOURCE 0

DRV .OPMODE 0

MOTOR .POLES 0

MOTOR .PHASE 0

DRV.EN

IL.CMDU 1   this needs to be selected based on your motor

MOTOR.PHASE 0

PL.FB

0

MOTOR.PHASE 30

PL.FB

910,225

MOTOR.PHASE 60

PL.FB

1820,445

MOTOR.PHASE 90

PL.FB

2730,67

……..

MOTOR.PHASE 359

PL.FB

10922,67

MOTOR.PHASE 30

PL.FB

11832,895

Calculate the position delta:

  • PL.FB [30 (2. Measurement)] - PL.FB [30 (1. Measurement)] = 11832,895 – 910,225 =  10922,67

The unit screen shows that you are getting a 16 bit value per rev of your feedback device:

imageCalculate motor pole pairs

  • Motor pole pairs = [16bit]/10922,67 = 65536 / 10922,67 = 6
  • MOTOR.POLES = 12

If the setup of the motor poles is completed it might be necessary to determine the commutation angle by doing a Wake and Shake.