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Motor Filter Reactors & Chokes

Motor filter reactors (or chokes) filter motor voltage and current, thus improving motor life and electrical noise levels within the application. Please contact us if you have problems with motor temperature or motor insulation life.

We provide reactors from low to very high frequency motor applications, up to about 1000 Volts and 1000 Amps. If sized properly, the application with motor filter reactor is practically always better than the application without one.

Motor filter reactor selection depends not only on motor current, voltage, frequency and type of application, but sometimes also on the length and type of motor wires or cables. SPINDEL Electronics uses modern simulation tools and an abundance of experience to specify an optimal reactor for every application.

Improper specification of motor filter reactor may result in application problems and even motor failure or failure of filter reactor itself.

spindel motor filter reactors chokes

Voltage and Insulation Issue

Short life of motor insulation can be a big problem in applications with long motor wires, but can also be an issue with short motor wires. Older motors, which were not originally designed for modern and aggressive transistor switching, typically do not have the insulation, which can run directly from a PWM drive.


With motor filter reactors, the voltage peaks of fast-switching modern PWM drives (over-shoot) and the rate of rise of voltage (dv/dt) are both reduced, making motor winding insulation last longer.

Motor Current Ripple (Harmonics) and Motor Temperature Issue

No drive output current is perfectly sinusoidal, resulting in additional motor losses. In some applications these additional losses are minimal, while in others are overwhelming.


Additional motor losses are caused by current ripple (current harmonics). The motor current ripple level depends on the drive which is used, motor data (motor equivalent circuit values), and filtering of drive output, if used.


Motor current ripple may or may not be a problem in a particular application, depending on motor load level, design margins, abundance of cooling, ambient temperature, and duty cycle.

spindel filter reactor


SPINDEL Electronics has the expertise and experience to provide the needed solutions to support your demanding applications. Our high frequency and spindle drives increase power efficiency and can lead to less down time on your production line.

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