How to Control BLDC Motors

Brushed motors are simple and effective but only offer speed control through change in voltage. Brushless motors offer a greater degree of control through a small solid-state computer.

Instead of carbon brushes powering the spinning rotor, an internal 3-phase inverter and electronic control are used.

How Does a BLDC Motor Work?

All electric motors convert electrical energy into rotational motion. Different types of motors achieve this in different ways.

A BLDC motor has two main components:

• A stator or stationary component which, when powered, creates and a constantly shifting magnetic field.
• A rotor or moving component which contains fixed magnets that spin within the shifting magnetic field.

To produce the magnetic field, a 3-phase inverter is used to alternate the distribution of voltage to magnetic coils (poles) spaced along the stator. The inverter is a series of switches that direct positive and negative voltage to the proper pattern of coils. By commutating the correct phases, the inverter creates a constant motion; this is known as trapezoidal control due to the shape of its energy wave.

The rotor contains magnets evenly spaced at 60-degree intervals. When different pairs of coils in the stator are energized, they simultaneously attract and repel the magnets in the rotor. The result is a spinning motion born from being pulled towards one coil and being pushed by its paired coil. By continually shifting which coils are pushing and pulling, the rotor spins.

How Does a Controller Work?

When the voltage input to a motor is constant, it spins at a constant speed. A commutation logic circuit calculates the pattern of phases within the magnetic field and energizes them accordingly. The inverter distributes voltage evenly.

The addition of a controller allows for a change in voltage. If the controller reduces the amount of voltage used to energize the engine, it will slow down. Concurrently, if the voltage is increased the motor will speed up.

Benefits of Controllers on BLDC Motors

As explained above, brushless motors offer more control due to their use of a 3-phase inverter and voltage controller.

When you have applications that require a more refined level of control, a BLDC motor may be the best option. They have become increasingly prominent in a variety of industries including:

• Automotive
• Aerospace
• Building Automation
• Floor Care
• Food & Beverage Equipment
• Home Appliances
• Medical / Patient Mobility
• Power Tools

See our Brushless Motor Controllers

What Motor Is Best for My Application?

There are a lot of options available. We have sourced and designed quality electric motors, including BLDCs, for over 30 years. Put our expert knowledge and extensive customer service to work for you. Call 763-383-6936 or contact us to get in touch with a friendly sales representative.