How to Control Electric Motors: A Guide to Motor Control for AC and DC Motors

KEY TAKEAWAYS

1. Motor controllers are vital in achieving precise control over electric motors for various applications.
2. Different types of motors, such as AC, brushed DC, and brushless DC, require specific control methods and corresponding motor controllers.
3. Motor controllers optimize energy consumption, improve motor efficiency, and extend motor lifespan.
4. The choice of motor controller depends on factors such as motor voltage, power requirements, control functions, and dimensional considerations.

Motion controllers, or motor controllers, for electric motors, are the brain of every motion control system. Their main task is to communicate to the motor precisely what it should do based on the desired outcome you would like from the motor. Motor controllers are used to maintain a set motor speed (speed control) or move to and hold a given position (position control) using feedback devices such as encoders that provide the necessary actual speed or position information.

At DNH we offer a wide range of controllers for maxon motors. These include motion controllers, motor controllers (current, speed & position), and positioning controllers.

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What are Motor and Motion Controllers?

Motor and motion controllers are used to operate the start, stop and run of a motor in a programmed manner. These controllers are used to gradually start or increase the speed of a motor, reverse the motor’s rotational direction, or increase the torque of a motor. Furthermore, they can be used for braking quadrants where the motor is decelerating. Controllers receive supply voltage information and provide signals to the motor drive.

Efficient motor control is important for optimizing the performance of motors and energy consumption. It can help reduce energy consumption and improve the efficiency of the motor. Efficient motor control can also help reduce wear and tear on the motor, which can help extend its lifespan. By optimizing the performance of motors, you can improve the overall performance of your system.

How are Motors Controlled?

An AC motor controller changes the frequency of the current to control the speed of the motor. The motor controller first turns that AC to DC then turns the DC back into AC at the right frequency. It uses a device called a rectifier to make DC current. The final step is making AC power at the right frequency. 

A brushed DC motor uses a controller to start and stop the rotation, change its direction, and manage the speed and torque. This is done by varying the supply voltage, varying the flux, and varying the current through the field winding. Brushed DC motors use brushes and commutators to switch the direction of the current. To perform these functions, a BDC motor controller regulates the current and voltage injected into the motor.

The speed of a brushless DC motor is controlled by the voltage and the torque is mainly controlled by the current. This is done by using a power transistor operating as a linear voltage regulator. Using a matching motor driver to change the output voltage of the driver to control the speed of the brushless motor. Motor controllers help you control the torque or speed of your brushless motor.

Positioning controllers are used for moving to and holding a given position (position control) or maintaining a set motor speed (speed control) using feedback devices such as encoders that provide the necessary actual speed or position information. To control the position of an AC motor, you can use an encoder. Encoders make motion control possible by sensing the motor’s speed and position and sending feedback signals to control components.

Sensors

To control speed, torque, position etc. you need sensors relaying actual motor information to the controller. There are various sensors: Encoders, tachometers, and resolvers. These sensors allow you to accurately evaluate the speed and angle position of your motor while providing a framework for high-precision, fine-tuned control loops.

Tachometers are instruments that measure the rotational speed of a shaft or disk. They usually display the revolutions per minute (RPM) on a calibrated analogue or digital display.

A resolver is an electromagnetic transducer that can be used in a wide variety of position and velocity feedback applications which includes light duty/servo, light industrial or heavy-duty applications. Resolvers are commonly used in servo motor feedback applications due to their good performance in high-temperature environments. Because the resolver is an analogue device and the electrical outputs are continuous through one complete mechanical revolution, the theoretical resolution of a single-speed resolver is infinite

Encoders, also known as rotary encoders or shaft encoders, are devices that convert mechanical motion or angular position into electrical speed or position information.

Read more about electric motors here

In conclusion, motor controllers are essential components in motion control systems, allowing precise regulation of speed, torque, and position outputs of electric motors. They facilitate efficient motor control, optimizing energy consumption and improving motor performance. The choice of the right motor controller depends on factors such as motor type, voltage, power requirements, and control functions. Additionally, feedback devices such as encoders, tachometers, and resolvers play a crucial role in providing accurate speed and position information for fine-tuned control. By selecting the appropriate motor controller and utilizing feedback sensors, one can achieve optimal motor performance and enhance the overall efficiency of the system.