**Category: **Toolbox > eDrives >** **eMotors
(Legacy) **> **Controllers > PWM Control

**Inputs:**

•**inhibit:** Provides immediate inhibiting of the output signal and
can be used with limit switches for out-of-range control. Active when input is
less than 0.3 V (active low).

•**input:** The amplifier input must be a positive voltage. The
amplifier saturates beyond the range of 0 – 100% modulation. To avoid
operation beyond saturation the input should be limited between 0 V and the
supply voltage divided by the amplifier gain.

•**current limit:** Sets the maximum average output current the
amplifier will provide. .

**Outputs:**

•**motor (+):** Provides the PWM control signal.

•**motor (-):** Referenced at a constant 0 V.

**Description:** The PWM Brush Motor 2Q-Current Feedback
block simulates a brush DC motor unipolar PWM amplifier (2 quadrant) with
current feedback that can be used for unidirectional motor control. The control
logic simulates a two-device inverter that allows PWM swing from 0 to the
specified supply voltage over a 0 – 100% modulation range. An inhibit
control is provided to disable amplifier output for a control voltage less than
0.3 V (logic low). Control of the PWM is accomplished through current
feedback control. Motor current is fed back through a current sense (resistor).
The controller for the current loop is PI; the integral and proportional gains
can be specified by you. By selecting appropriate values of PI proportional and
integral gain, current loop dynamics can be adjusted for any motor. Logic is
provided that clamps the output to limit load current according to the specified
current limit. Anti-windup control is provided in the integrator.

To provide adequate simulation of PWM behavior, the simulation step size should be considerably smaller than the inverse of the selected PWM frequency; preferably at least 100 times smaller.

Direct access to the PWM can be accomplished by setting the current sense gain and current loop integral gain equal to 0, and the current loop proportional gain equal to 1. In this situation, current limiting is still available as long as motor current output is connected to the current sense input.

**Current Loop Integral Gain:** Typically sets the speed
and tracking accuracy (bandwidth) of the current control loop.

**Current Loop Proportional Gain:** Typically sets the
damping of the current control loop.

**Current Sense Gain:** Sets the gain of the current
feedback-sensing device.

**PWM Frequency:** sets the carrier frequency for the
PWM. Note that to provide adequate simulation of PWM behavior, the simulation
step size should be chosen to be considerably smaller than the inverse of the
selected PWM frequency; preferably at least 100 times smaller.

**Supply Voltage:** sets the voltage level output of the
PWM.

**Diagram name: **PWM Brush Amplifier 2Q WCF

**Location: **Examples > eDrives and Systems >
eMotors (Legacy) > Brush DC

This example illustrates how the PWM amplifier can be used to directly regulate a set current in a DC motor. Such a control loop may be used to control against torque disturbance since torque is directly proportional to motor current. Here the supply voltage is set at 180 V, and PWM frequency is 9000 Hz. Proportional gain is set at 0, so the control is pure integral with a gain of 50. The current sense gain is 1, so the average controlled current should approach the set current of 1.5 amps.