Zikodrive Motor Controllers - stepper motor drivers, brushless ESCs, bldc motor drivers, stepper motor controllers
Zikodrive Motor Controllers - stepper motor drivers, brushless ESCs, bldc motor drivers, stepper motor controllers

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How does back-EMF control of sensorless brushless motors work and what brushless motor controllers do I need to use this?


Back EMF stands for Back Electromotive Force. In simple terms, the Back EMF is an electromotive force which occurs as the brushless motor turns and acts like a generator. Critically the Back EMF generated by the brushless motor can be measured by certain types of sensorless brushless motor controller such as the ZDBL15 Brushless Motor Controller. As the frequency of the BACK EMF is directly proportional to the speed of the motor this then enables the sensorless brushless motor controller to know exactly what speed the BLDC motor is rotating at.

An intelligent motor controller such as the ZDBL15 brushless ESC can then read this force and use it to measure the actual speed of the motor. This speed can then be maintained using Back EMF as a reference to measure and adjust the speed. It is this method which enables a sensorless brushless motor controller such as the ZDBL15 to be able to deliver constant speed under a variable load.


A disadvantage of using this method is that no back EMF is generated when the motor is stationary, meaning that start up is affected by operating in open loop. As a result of this, the motor can take a small amount of time to settle and run efficiently. A second disadvantage is that at low speeds the back EMF is small and therefore can be quite difficult to measure accurately, which can result in inefficient operation. For situations where low speed is required it is worth considering either sensored motors or stepper motors.


Using back-EMF as a means of maintaining and accurately controlling motor speed in brushless DC motors is a much lower cost solution than brushless DC motors with sensors and is also much more reliable as there are less component parts which can go wrong. It is important to remember that a brushless DC motor with hall effect sensors and a brushless dc motor controller which is designed purely for use with sensors will become completely useless if the sensors begin to fail. However, a sensorless brushless motor controller such as the ZDBL15 will be able to continue reliably functioning without the risk of sensor failure because it does not need them.

To browse the range of ZDBL Series Brushless Motor Controllers which optimise back-EMF to deliver exceptionally accurate brushless motor control please CLICK HERE

If you have any additional questions please CONTACT US to discuss or have a look at some specific CASE STUDIES or FREQUENTLY ASKED QUESTIONS.

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Why not start by browsing some of the ZDBL Series of Sensorless Brushless Motor Controllers which feature BACK EMF as a key part of the way in which they operate. You can view the Vert Rotor case study to see how the ZDBL15 has been used in a high end compressor application and as always, if you have any questions, please CONTACT US.

Brushless Motors ControllersVert Rotor Case StudyZDBL10 - 10A Brushless ESC or BLDC Motor Driver with Sensorless Brushless Motor Controller using back EMF to maintain constant speed

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Frequently Asked Questions

Can I replace a DC motor with a brushless DC motor and controller?

How fast can a stepper motor go?

How complex can the programming on the Zikodrive stock range of motor controllers be?

Can sensorless brushless motor controllers be used in dosing applications?

Can a sensorless brushless motor be started efficiently under load?

Can I purchase the IP rights to a bespoke designed controller?

Do you offer on site support and assistance setting up a new controller?

What are the typical costs associated with modifying an existing stock stepper motor controller or brushless motor driver?

Can I run a motor at a fixed speed under a variable or changing load?