Documentation

# Simplified PMSM Drive

Brushless motor model with closed-loop torque control

• Library:
• Simscape / Electrical / Electromechanical / Permanent Magnet ## Description

The Simplified PMSM Drive block represents a brushless motor model with closed-loop torque control. This block abstracts the torque-speed behavior of the combined motor and motor driver in order to support system-level simulation where simulation speed is important.

The block permits only the range of torques and speeds that the torque-speed envelope defines. In the default block configuration, you specify this data in the block dialog box as a set of speed data points and corresponding maximum torque values. The following figure shows a typical torque-speed envelope for a servomotor. Specify the torque-speed envelope for the positive torque region only, that is, quadrants 1 and 4. If you specify only for positive speeds (quadrant 1 or, equivalently, the motoring region), then the quadrant 4 torque envelope is defined by the block as the mirror image of quadrant 1. The servomotor torque-speed envelope has the same profile when the motor is operating in a reverse direction (quadrants 2 and 3).

Instead of providing tabulated torque-speed data, you can specify a maximum torque and a maximum power. This results in the torque-speed envelope profile shown below. The other three operating quadrants are constrained by this same profile. The block produces a positive torque acting from the mechanical C to R ports.

### Modeling Electrical Losses

The block allows both simplified and tabulated definition of electrical losses. The default, simplified, behavior is to model the losses as the sum of the following four terms:

• A series resistance between the DC power supply and the motor drive.

• Fixed losses independent of torque and speed, P0. Use this to account for fixed converter losses.

• A torque-dependent electrical loss kτ2, where τ is the torque and k is a constant. This represents ohmic losses in the copper windings.

• A speed-dependent electrical loss kwω2, where ω is the speed and kw is a constant. This represents iron losses due to eddy currents.

Alternatively, you can provide tabulated loss values as a function of motor speed and load torque. When using this option, provide data for all of the operating quadrants that your simulation will run in. If you provide partial data (for example, just for the quadrant 1 forward motoring region), then the other quadrants are assumed to repeat the same pattern of losses. This will normally be correct for the reverse motoring region, but may be an approximation for the braking/generating quadrants. The block does no extrapolation of loss values for speed and torque magnitudes that exceed the range of the table.

Finally, you can specify electrical losses by using tabulated efficiency data, instead of a single efficiency measurement or tabulated loss data. When using this option, also provide data for all of the operating quadrants that your simulation will run in. If you provide partial data (for example, just for the quadrant 1 forward motoring region), then the other quadrants are assumed to repeat the same pattern of losses.

The best practice is to provide tabulated loss data as a function of speed and torque, rather than tabulated efficiency data, because:

• Efficiency becomes ill-defined for zero speed or zero torque.

• Using losses, you can also account for fixed losses that are still present for zero speed or torque.

If you use the tabulated efficiencies option:

• The block converts the efficiency values you provide into losses and uses the tabulated losses for simulation.

• Efficiency values you provide for zero speed or zero torque are ignored, and losses are assumed zero when either torque or speed is zero.

• The block uses linear interpolation to determine losses. Provide tabulated data for low speeds and low torques, as required, to get the desired level of accuracy for lower power conditions.

• The block does no extrapolation of loss values for speed and torque magnitudes that exceed the range of the table.

When you provide tabulated loss or efficiency data, you can also specify it as a function of speed, load torque, and DC supply voltage. This option is useful when the supply voltage is not regulated and can vary during the simulation. One example is an electric vehicle drivetrain that does not have a DC-DC regulator upstream of the motor drive. Use the Simplified PMSM Drive block to model the motor drive and provide tabulated loss or efficiency values as a function of motor speed, load torque, and DC supply voltage.

### Block Variants

The block provides four modeling variants, accessible by right-clicking the block in your block diagram and then selecting the appropriate option from the context menu, under Simscape > Block choices:

• No thermal port — Basic model that does not simulate faults or thermal effects. This is the default.

• Show thermal port — Model with exposed thermal port. This model does not simulate faults.

• Faultable| No thermal port — Model with exposed fault control port. This model does not simulate thermal effects.

• Faultable | Show thermal port — Model that lets you simulate both faults and thermal effects. Both the thermal port and the fault input port are exposed.

### Thermal Ports

The block has an optional thermal port, hidden by default. To expose the thermal port, select one of the block variants that model thermal effects, as described in Block Variants. This action displays the thermal port H on the block icon, and exposes the Temperature Dependence and Thermal Port parameters . These parameters are described further on this reference page.

Use the thermal port to simulate the effects of copper resistance losses that convert electrical power to heat. For more information on using thermal ports in actuator blocks, see Simulating Thermal Effects in Rotational and Translational Actuators.

### Simulating Faults

You can use the physical signal input port F to simulate servomotor failure, as well as connecting and disconnecting the DC supply. You cannot simulate disconnecting the DC supply by simply opening a switch, because there must be a finite voltage on the servomotor terminals, producing the current that balances the electrical and mechanical power.

To expose the fault control port, select one of the faultable block variants, as described in Block Variants. This action displays the physical signal input port F on the block icon, and adds the Faults tab to the block dialog box. This tabs are is described further on this reference page.

If a signal is connected to port F, then the block operates according to the parameter settings on the Faults tab. For example, if Fault condition is ```Faulted if F >= Fault threshold```, then when the signal at port F rises above the Fault threshold value, the servomotor stops operating, zero current is taken from the supply side, and zero current is supplied to the load side.

## Assumptions and Limitations

• The motor driver tracks a torque demand with a time constant Tc.

• Motor speed fluctuations due to mechanical load do not affect the motor torque tracking.

## Ports

### Input

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Physical input port associated with the reference torque demand.

Physical input port associated with the servomotor failure simulation.

#### Dependencies

This port is visible only when you choose the faultable block variant, as described in Block Variants..

### Output

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Physical output port associated with the mechanical speed.

### Conserving

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Electrical conserving port associated with the positive electrical DC supply.

Electrical conserving port associated with the negative electrical DC supply.

Mechanical rotational conserving port associated with the motor case.

Mechanical rotational conserving port associated with the motor rotor.

## Parameters

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### Electrical Torque

Select one of the following methods for block parameterization:

• `Tabulated torque-speed envelope` — Provide the vectors of rotational speeds and corresponding maximum torque values. This is the default option.

• `Maximum torque and power` — Define the torque-speed envelope by providing values for maximum permissible torque and motor power.

Rotational speeds for permissible steady-state operation. To avoid poor performance due to an infinite slope in the torque-speed curve, specify a vector of rotational speeds that does not contain duplicate consecutive values.

#### Dependencies

This parameter is visible only when you set the Parameterize by parameter to ```Tabulated torque-speed envelope```.

Maximum torque values for permissible steady-state operation. These values correspond to the speeds in the Vector of rotational speeds parameter and define the torque-speed envelope for the motor.

#### Dependencies

This parameter is visible only when you set the Parameterize by parameter to ```Tabulated torque-speed envelope```.

The maximum permissible motor torque.

#### Dependencies

This parameter is visible only when you set the Parameterize by parameter to `Maximum torque and power`.

The maximum permissible motor power.

#### Dependencies

This parameter is visible only when you set the Parameterize by parameter to `Maximum torque and power`.

Time constant with which the motor driver tracks a torque demand.

### Electrical Losses

Select one of the following methods for electrical loss parameterization:

• `Single efficiency measurement` — Model the losses as the sum of the four terms, listed in the block description, at a single measurement point.

• ```Tabulated loss data as a function of speed and torque``` — Determine the losses by two-dimensional table lookup based on the provided tabulated data for motor speeds, load torques, and corresponding losses.

• ```Tabulated efficiency data as a function of speed and torque``` — Determine the losses by two-dimensional table lookup based on the provided tabulated data for motor speeds, load torques, and corresponding efficiencies.

• ```Tabulated loss data as a function of speed, torque, and DC supply voltage``` — Determine the losses by three-dimensional table lookup based on the provided tabulated data for motor speeds, load torques, DC supply voltages, and corresponding losses.

• ```Tabulated efficiency data as a function of speed, torque, and DC supply voltage``` — Determine the losses by three-dimensional table lookup based on the provided tabulated data for motor speeds, load torques, DC supply voltages, and corresponding efficiencies.

See Modeling Electrical Losses for details.

The block defines overall efficiency as

`$\eta =100\frac{{\tau }_{0}{\omega }_{0}}{{\tau }_{0}{\omega }_{0}+{P}_{0}+k{\tau }_{0}^{2}+{k}_{w}{\omega }_{0}^{2}}$`

where:

• τ0 represents the Torque at which efficiency is measured.

• ω0 represents the Speed at which efficiency is measured.

• P0 represents the Fixed losses independent of torque or speed.

• $k{\tau }_{0}^{2}$ represents the torque-dependent electrical losses.

• kwω2 represents the speed-dependent iron losses.

At initialization, the block solves the efficiency equation for k. The block neglects losses associated with the rotor damping.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to `Single efficiency measurement`.

Speed that the block uses to calculate torque-dependent electrical losses.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to `Single efficiency measurement`.

Torque that the block uses to calculate torque-dependent electrical losses.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to `Single efficiency measurement`.

Iron losses at the speed and torque at which efficiency is defined.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to `Single efficiency measurement`.

Fixed electrical loss associated with the driver when the motor current and torque are zero.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to `Single efficiency measurement`.

The vector of speed values, to be used for table lookup when calculating losses.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to ```Tabulated loss data as a function of speed and torque```, ```Tabulated loss data as a function of speed, torque, and DC supply voltage```, ```Tabulated efficiency data as a function of speed and torque```, or ```Tabulated efficiency data as a function of speed, torque, and DC supply voltage```.

The vector of speed values, to be used for table lookup when calculating losses.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to ```Tabulated loss data as a function of speed and torque```, ```Tabulated loss data as a function of speed, torque, and DC supply voltage```, ```Tabulated efficiency data as a function of speed and torque```, or ```Tabulated efficiency data as a function of speed, torque, and DC supply voltage```.

The vector of DC supply voltages, to be used for table lookup when calculating losses.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to ```Tabulated loss data as a function of speed, torque, and DC supply voltage``` or ```Tabulated efficiency data as a function of speed, torque, and DC supply voltage```.

Tabulated values for electrical losses as a function of speed and torque, to be used for 2D table lookup. Each value in the matrix specifies the losses for a specific combination of speed and torque. The matrix size must match the dimensions defined by the speed and torque vectors.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to ```Tabulated loss data as a function of speed and torque```.

Tabulated efficiency values, in percent, as a function of speed and torque, to be used for 2D table lookup. Each value in the matrix specifies the efficiency for a specific combination of speed and torque. The matrix size must match the dimensions defined by the speed and torque vectors. Efficiency values you provide for zero speed or zero torque are ignored, and losses are assumed zero when either torque or speed is zero. The block uses linear interpolation to determine losses. Provide tabulated data for low speeds and low torques, as required, to get the desired level of accuracy for lower power conditions.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to ```Tabulated efficiency data as a function of speed and torque```.

Tabulated values for electrical losses as a function of speed, torque, and DC supply voltage, to be used for 3D table lookup. Each value in the matrix specifies the losses for a specific combination of speed, torque, and DC supply voltage. The matrix size must match the dimensions defined by the three vectors.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to ```Tabulated loss data as a function of speed, torque, and DC supply voltage```.

Tabulated efficiency values, in percent, as a function of speed, torque, and DC supply voltage, to be used for 3D table lookup. Each value in the matrix specifies the efficiency for a specific combination of speed, torque, and DC supply voltage. The matrix size must match the dimensions defined by the three vectors. Efficiency values you provide for zero speed or zero torque are ignored, and losses are assumed zero when either torque or speed is zero. The block uses linear interpolation to determine losses. Provide tabulated data for low speeds and low torques, as required, to get the desired level of accuracy for lower power conditions.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter to ```Tabulated efficiency data as a function of speed, torque, and DC supply voltage```.

The equivalent resistance used in series with the DC supply to model electrical losses that are proportional to the driver supply current. The block assumes that the DC supply current is approximately constant under constant load conditions.

### Faults

Selects whether the fault is triggered by a signal that is high or low:

• `Faulted if F >= Fault threshold`Simplified PMSM Drive block is disabled if the signal at port F rises above the threshold value.

• `Faulted if F <= Fault threshold`Simplified PMSM Drive block is disabled if the signal at port F falls below the threshold value.

The threshold value used to detect a fault.

### Mechanical

Rotor resistance to change in motor motion. The value can be zero.

Rotor damping. The value can be zero.

Rotor speed at the start of the simulation.

### Temperature Dependence

Parameter α in the equation defining resistance as a function of temperature, as described in Thermal Model for Actuator Blocks. This parameter is visible only if the Parameterize losses by parameter on the Electrical Losses tab is set to `Single efficiency measurement`. The default value is for copper.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter on the Electrical Losses setting to `Single efficiency measurement`.

The temperature for which motor parameters are defined. If you parameterize electrical losses by tabulated loss data, then this is the temperature for which the Corresponding losses, P(w,T) are given on the Electrical Losses tab.

The temperature for which the Corresponding losses, P(w,T), at second measurement temperature are given.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter on the Electrical Losses setting to `Tabulated loss data`.

Iron losses at the second measurement temperature, corresponding to the speed and torque tabulated values on the Electrical Losses tab.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter on the Electrical Losses setting to `Tabulated loss data`.

Tabulated efficiency values, in percent, at the second measurement temperature, corresponding to the speed and torque tabulated values on the Electrical Losses tab.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter on the Electrical Losses setting to ```Tabulated efficiency data as a function of speed and torque```.

Iron losses at the second measurement temperature, corresponding to the speed, torque, and DC supply voltage tabulated values on the Electrical Losses tab.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter on the Electrical Losses setting to ```Tabulated loss data as a function of speed, torque, and DC supply voltage```.

Tabulated efficiency values, in percent, at the second measurement temperature, corresponding to the speed, torque, and DC supply voltage tabulated values on the Electrical Losses tab.

#### Dependencies

This parameter is visible only when you set the Parameterize losses by parameter on the Electrical Losses setting to ```Tabulated efficiency data as a function of speed, torque, and DC supply voltage```.

### Thermal Port

Thermal mass of the electrical winding, defined as the energy required to raise the temperature by one degree.

The temperature of the thermal port at the start of simulation. The default value is `25``°C`.