Speed Controller Repair


An speed controller is an electronic circuit designed with the goal of varying the speed and direction of an electric motor, and also to provide the possibility to act as a dynamic brake. This can be used for both DC motors (brushless or brushed) and also for AC motors (single or three phases).


Regardless of the type of motor, all speed controllers require feedback information from the motor.  This task is performed by devices called transducers used to accurately resolve and encode the position of a motor shaft  or linear movement on a machine. Through the history of machine development the common names adopted for these devices are the resolver and the encoder.



The resolver is basically a small transformer which effective turns ratio and polarity between the primary and the secondary winding varies depending on the angle of the shaft.  Due to changes in positions between the two windings of the resolver during the shaft rotation, the output signal will be two sinusoidal signals – one for each of the two windings – which will have a phase difference depending of motor speed value(analog output).



The incremental encoder generates two output signals using evenly slots  on an opaque disk. On one side of the disk is a light source and on the opposite side disk are two light detectors. The disk is mounted on the motor shaft while light source and detectors are stationary. As the disk rotates, each the detectors will sense changes when a slot appear in the path of the light. Each encoder depend on the number of slots on the disk. Encoders produce pulses (digital output) indicating movement over a short distance; by counting  these pulses information about speed can be obtained and by checking the order of pulses in the two channels will generate information about rotation direction.


Using these information the speed controller implement a very reliable closed loop system, with the following advantages:

  • Reducing errors by automatically adjusting the system input to get the desired speed;
  • Improving stability to external load conditions;
  • Enhancement of robustness against external disturbances to the process;
  • Producing a reliable and repeatable performance.


Depending of the level of control required and on motor power the electronics implemented in speed controller could vary from simple circuits (for DC motor for example) to very complex designs, with various interfacing and programming capabilities.


Our team of highly qualified technicians can perform professional speed controller repair. We have the experience required, and also the test equipment needed to find the problem of any unit, regardless of its complexity. After the fault is found we will provide you an estimation of the repair cost, leaving you to decide if the repair will be done. Usually the repair cost is less than 50% of the price of a new unit.


After the approval, we will repair the speed controller and test it properly to assure the customer that the unit will comply with all the manufacturer specified characteristics. We will guarantee our repair with up to a full year warranty.

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