Using the motor's data sheet, the user can
input the maximum motor electrical speed in Hz using the maxMotorSpeed parameter in
the System Configuration Page. If this data is not available, the user can input the
number of pole pairs and motor mechanical speed in RPM. The user can convert the motor
mechanical speed in RPM to motor electrical speed in Hz using Equation 10.
Equation 10.
Where:
- ωMechanical is the
mechanical speed in units revolutions per minute (RPM)
- fElectrical is the
electrical speed in units of hertz (Hz)
- nPolePairs is the
number of motor pole pairs
Note:
To determine the number of motor poles
without a motor data sheet:
- Use a lab power supply and make sure
the current limit is set to less than the motor rated current. Do not turn on the
supply.
- Connect V+ of the supply to phase A and
V- of the supply to phase B of the motor. Any 2 of the 3 phases can be chosen at random
if the phases not labeled.
- Turn on supply, The rotor settles at
one position by injecting current.
- Manually rotate the rotor until rotor
snaps to another settle position. Rotor settle down at various positions around one
mechanical cycle.
- Count the number of settle-down
positions for one fully mechanical cycle, which is the number of pole pairs. Multiplying
by two calculates the number of poles.
Be careful of gearing systems within a
motor. The gearing ratio determines how many rotor revolutions correlate to the shaft
mechanical revolution.