SimElectronics™

Universal Motor

Model electrical and torque characteristics of a universal (or series) motor

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Actuators & Drivers

Description

The Universal Motor block represents the electrical and torque characteristics of a universal (or series) motor using the following equivalent circuit model.

Where:

R_a is the armature resistance.
L_a is the armature inductance.
R_f is the field winding resistance.
L_f is the field winding inductance.

When you set the Model parameterization parameter to By equivalent circuit parameters, you specify the equivalent circuit parameters for this model. The Universal Motor block computes the motor torque as follows:

The magnetic field in the motor induces the following back emf v_b in the armature:

where L_af is a constant of proportionality and ω is the angular velocity.
The mechanical power is equal to the power reacted by the back emf:
The motor torque is:

The torque-speed characteristic for the Shunt Motor block model is related to the parameters in the preceding figure. When you set the Model parameterization parameter to By DC rated power, rated speed & maximum torque or By DC rated power, rated speed & electrical power, the block solves for the equivalent circuit parameters as follows:

For the steady-state torque-speed relationship when using a DC supply, L has no effect.
Sum the voltages around the loop:
Solve the preceding equation for i_f and substitute this value into the equation for torque:

The block uses the rated speed and power to calculate the rated torque. The block uses the rated torque and rated speed values in the preceding equation plus the corresponding electrical power to determine values for R_f+R_a and L_af.

When you set the Model parameterization parameter to By AC rated power, rated speed, current & electrical power, then the block must include the inductive terms L_a and L_f in the model. This requires information about the RMS rated current and voltage for the total inductance.

The block models motor inertia J and damping B for all values of the Model parameterization parameter. The output torque is:

The block produces a positive torque acting from the mechanical C to R ports.

Dialog Box and Parameters

Electrical Torque Tab

Model parameterization

Select one of the following methods for block parameterization:

By equivalent circuit parameters — Provide electrical parameters for an equivalent circuit model of the motor.
By DC rated power, rated speed & maximum torque — Provide DC power and speed parameters that the block converts to an equivalent circuit model of the motor. This is the default method.
By DC rated power, rated speed & electrical power — Provide AC power and speed parameters that the block converts to an equivalent circuit model of the motor.
By AC rated power, rated speed, current & electrical power — Provide AC power and speed parameters that the block converts to an equivalent circuit model of the motor.

Total armature and field winding resistance

Total resistance of the armature and field winding. This parameter is only visible when you select By equivalent circuit parameters for the Model parameterization parameter. The default value is 132.8 Ω.

Rated speed (at rated load)

Motor speed at the rated mechanical load. This parameter is only visible when you select By DC rated power, rated speed & maximum torque, By DC rated power, rated speed & electrical power, or By AC rated power, rated speed, current & electrical power for the Model parameterization parameter. The default value is 6.5e+03 rpm.

Rated load (mechanical power)

The mechanical load for which the motor is rated to operate. This parameter is only visible when you select By DC rated power, rated speed & maximum torque, By DC rated power, rated speed & electrical power, or By AC rated power, rated speed, current & electrical power for the Model parameterization parameter. The default value is 75 W.

Rated DC supply voltage

The DC voltage at which the motor is rated to operate. This parameter is only visible when you select By DC rated power, rated speed & maximum torque or By DC rated power, rated speed & electrical power for the Model parameterization parameter. The default value is 200 V.

Electrical power in at rated load

The amount of electrical power the motor uses at the rated mechanical power. This parameter is only visible when you select By DC rated power, rated speed & electrical power or By AC rated power, rated speed, current & electrical power for the Model parameterization parameter. The default value is 160 W.

Maximum (starting) torque

Maximum torque the motor produces. This parameter is only visible when you select By DC rated power, rated speed & maximum torque for the Model parameterization parameter. The default value is 0.39 N*m.

Total armature and field winding inductance

Total inductance of the armature and field winding. If you do not have information about this inductance, set the value of this parameter to a small, nonzero number. This parameter is only visible when you select By equivalent circuit parameters, By DC rated power, rated speed & maximum torque, or By DC rated power, rated speed & electrical power for the Model parameterization parameter. The default value is 0.525 H.

Note You can set the Total armature and field winding inductance value to zero, but this only makes sense if you are driving the motor with a DC source.

RMS rated voltage

RMS supply voltage when the motor operates on AC power. This parameter is only visible when you select By AC rated power, rated speed, current & electrical power for the Model parameterization parameter. The default value is 240 V.

RMS current at rated load

RMS current when the motor operates on AC power at the rated load. This parameter is only visible when you select By AC rated power, rated speed, current & electrical power for the Model parameterization parameter. The default value is 0.8 A.

AC frequency

Frequency of the AC supply voltage. This parameter is only visible when you select By AC rated power, rated speed, current & electrical power for the Model parameterization parameter. The default value is 50 Hz.

Mechanical Tab

Rotor inertia: Rotor inertia. The default value is 2e-04 kg*m². The value can be zero.
Rotor damping: Rotor damping. The default value is 1e-06 N*m/(rad/s). The value can be zero.
Initial rotor speed: Speed of the rotor at the start of the simulation. The default value is 0 rpm.

Ports

The block has the following ports:

+: Positive electrical port.
-: Negative electrical port.
C: Mechanical rotational conserving port.
R: Mechanical rotational conserving port.

References

[1] Bolton, W. Mechatronics: Electronic Control Systems in Mechanical and Electrical Engineering 3rd edition, Pearson Education, 2004.