Rotary PM Motor Attributes

These are the motor configuration attributes that apply specifically to rotary motor types.

PM Motor Rated Torque

The PM Motor Rated Torque attribute is floating point value that specifies the nameplate continuous torque rating of a rotary permanent magnet motor.

PM Motor Torque Constant

The PM Motor Torque Constant attribute is a floating point value that specifies the torque constant, Kt, of a rotary permanent magnet motor in Newton-meters per RMS Amp.

PM Motor Rotary Voltage Constant

The PM Motor Rotary Voltage Constant attribute is a float that specifies the voltage, or back-EMF, constant of a rotary permanent magnet motor in phase-to-phase RMS Volts per KRPM.

If the optional PM Motor Torque Constant, Kt, is not explicitly supported in the implementation the value may be computed from the PM Motor Rotary Voltage Constant, Ke, according to this equation: Kt (N-m/A

rms

) = 0.01654 * Ke (V

rms

/Krpm).

PM Motor Rotary Bus Overvoltage Speed

This value corresponds to the rotary motor speed at which the back-EMF of the motor equals the maximum operational bus voltage of the drive. When the extended speed range of a PM motor is not permitted, this value can be used to limit motor speed to protect the drive from damage caused from bus overvoltage conditions that occur when disabling a PM motor at high speed.

When configured for Position Loop or Velocity Loop operation, this bus overvoltage protection includes limiting the magnitude of the velocity reference value allowed into the velocity summing junction to the Bus Overvoltage Speed Limit value using the velocity limiter function. If the signal entering the velocity limiter exceeds this velocity limit value, and the PM Motor Extended Speed Permissive is False, the velocity limiter clamps the velocity reference to this value and sets the Velocity Limit status bit. If the PM Motor Extended Speed Permissive is True, or the value of this attribute is 0, this limit is not applied.

When the extended speed range of a PM motor is not permitted, overvoltage protection is also provided through motor overspeed detection based on the Motor Overspeed Factory Limit and Motor Overspeed User Limit. Exceeding these limits results in a Motor Overspeed FL or UL Axis Exception. Overspeed detection is the only source of protection when the axis is configured for Torque Loop operation.

PM Motor Rotary Max Extended Speed

When the extended speed range of a PM motor is permitted (PM Motor Extended Speed Permissive is True), this value can be used to limit the speed of a rotary motor to protect the motor or load from damage due to an overspeed condition.

When configured for Position Loop or Velocity Loop operation, this overspeed protection includes limiting the magnitude of the velocity reference value allowed into the velocity summing junction using the velocity limiter function. If the signal entering the velocity limiter exceeds this velocity limit value, the velocity limiter clamps the velocity reference to this value and sets the Velocity Limit status bit. If the value of this attribute is 0, this limit is not applied.

When the extended speed range of a PM motor is permitted, overspeed protection is also provided through motor overspeed detection based on the Motor Overspeed Factory Limit and Motor Overspeed User Limit. Exceeding these limits results in a Motor Overspeed FL or UL Axis Exception. Overspeed detection is the only source of protection when the axis is configured for Torque Loop operation.

If the related optional attribute, Rotary or Linear Motor Max Speed, is supported, software will apply this maximum speed value as the Max Value for this attribute.