# SRM Commutation

Generate switching sequences for *n*-phase switched reluctance
motor (SRM)

*Since R2022b*

**Libraries:**

Motor Control Blockset /
Controls /
Control Reference

## Description

The SRM Commutation block implements a commutation system that generates
switching sequences to energize the stator windings of an *n*-phase
SRM.

The block supports either a three-, four-, five-, or six-phase SRM.

For more details about the algorithm used by the block, see Algorithm.

## Examples

## Ports

### Input

### Output

## Parameters

## Algorithms

The block uses the electrical motor position
(*θ _{e}*), electrical turn-on position
(

*θ*), and electrical turn-off position (

_{eOn}*θ*) to generate

_{eOff}*n*switching sequences (a vector of size

*n*) for an

*n*-phase SRM.

Each switching sequence (that forms a pulse train) can be used to control (turn on or off) the corresponding motor phase.

Each pulse in a switching sequence represents the activation period of the phase. The
range of motor positions for which a phase activates is known as the dwell angle,
*θ _{dwell}* =

*θ*–

_{eOff}*θ*. When the motor electrical position falls within the dwell angle of a phase, the block outputs 1 to activate this phase.

_{eOn}For the first stator phase or phase A is as follows.

Block output | Condition | ||
---|---|---|---|

0 | if θ or
_{eOn}θ >
_{e}θ_{eOff} | ||

1 | if θ ≤
_{e}θ_{eOff} |

For subsequent phases, the block output (switching sequence) has an offset of
`(m⨯2π)/n`

for the `m`

motor
phase (^{th}*m* is a value between `0`

and *n*
and *n* is the total number of motor phases).

Therefore, for an *n*-phase SRM, the block output is a combination of
*n* such sequences (or pulse trains) that can be used with position sensor
feedback and control loops to control the motor speed.

The direction in which the motor rotates depends on the sequence in which you excite the
stator phases. You can use the block output to change this excitation sequence by providing
appropriate inputs at *θ _{eOn}* and

*θ*.

_{eOff}The block expects that the electrical motor position
(*θ _{e}*) input is aligned with the first phase of the
SRM (phase a or phase 1). The block internally computes the remaining electrical positions
aligned with the subsequent phases and generates switching sequences for them. For example,
for a 3-phase SRM, if you derive the

*θ*input from the mechanical motor position aligned with motor phase

_{e}*a*, then the block internally computes the required electrical positions for phases

*b*and

*c*and generates the commutation outputs for each of the three phases.

**Note**

The block inputs should have the same position units.

## Extended Capabilities

## Version History

**Introduced in R2022b**

## See Also

PI Controller | Switched Reluctance Machine (Simscape Electrical)