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What is Pulse Width Modulation?

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Thu, Jan 12, 2017 @ 11:35 AM

What is PWM

The latest entry in the Magnet-Schultz of America Solenoid 101 blog discusses how pulse width modulation can be used to increase the power efficiency of solenoids and other devices. A more detailed analysis of these types of mechanisms has been previously published by MSA here. This recap will reduce the content to the simplest terms for a quick and clear understanding of the fundamental concepts. Check our blog history for information on more technical subjects and feel free to make suggestions for future posts.

 

What is Pulse Width Modulation?

Pulse width modulation, or PWM, is a way to digitally manipulate the power supplied to a solenoid or other device to increase efficiency. This is done by reducing the amount of power supplied during the portions of the operating cycle that do not require the full supply voltage.

While the solenoid is pushing or pulling a load, the power requirement peaks. The energy required to overcome the inertia of the load is much higher than what is required to hold the load after the plunger is fully seated. When using standard power supply the voltage is constant, so the voltage applied must match the peak power requirement. This means that the full voltage is also being applied through the full operating cycle of the device.  PWM allows for the manipulation of power so that the supply can be reduced while the plunger is fully seated.

A Magnet-Schultz of America PWM Unit

Pulse Width Modulation PCB

How Does PWM Work?

The PWM board modulates power by switching it off and on according to a specified duty cycle at a high frequency. The duty cycle is the ratio of on and off time. This ratio of on and off time creates an average output voltage which becomes the input voltage for the device. The frequency this cycle is repeated is fast enough that the device does not respond to the on/off switching and instead only responds to the average.

Generally, the amount of energy saved is not a significant enough benefit by itself to warrant the use of PWM. The secondary benefit of reduced coil heat is a greater advantage. Reduced heat means that the solenoid can operate at higher duty cycles or provide higher peak force without sacrificing performance. With a standard power supply increasing the duty cycle without reducing the force would require a larger unit. PWM is ideal for actuator devices that need increased performance in a constrained package size.

The PWM driver itself is a printed circuit board connected to the device. The two can be designed as a single self-contained unit or can be implemented separately. Magnet-Schultz of America can engineer and supply PWM boards custom suited to a particular actuator, guaranteeing optimum efficiency and ease of implementation.

Magnet-Schultz of America specializes in the custom engineering and manufacturing of solenoids, solenoid valves, electromagnets, voice coils, hydraulic tubes and coils, and locking devices. If you have any questions related to sourcing or manufacturing, please contact us. We will be happy to assist in the development of your application. Browse past blogs for a more in-depth look at solenoid functions and subscribe to the notifications for future posts!

Topics: Coil Temperature Control