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.