Why do some DC moto...
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Why do some DC motors come with a capacitor across them while others do not?

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Topic starter

Hey guys,

I have purchased a lot of DC motors from different sources recently. Some of them have capacitors soldered across them, while some do not. Why is this so?

1 Answer

The presence of capacitors is all about dealing with electrical noise and interference.

1) When you spin a DC motor, it actually tries to fight back a little bit by generating its own voltage, called back EMF. This can cause some voltage spikes when the motor starts or stops. The capacitor helps absorb those spikes and keep the power supply happy.

2) Brushed DC motors, can generate sparks as the brushes switch between contacts. This sparking creates high-frequency electrical noise that can mess with nearby electronics and even cause radio interference (EMI). The capacitor acts like a tiny little battery, absorbing those quick bursts of current and smoothing things out.

Now coming to the question, why don't all DC motors have them?

Not all manufacturers include capacitors in their motors, especially in low-cost or basic motors where cost and simplicity are prioritized.

In some cases, you are expected to add your own capacitors based on the specific application needs.

TechSpark Topic starter 09/07/2024 9:14 am

@ankunegi Thanks for the explanation! If I want to add capacitors to a motor that doesn't have them, what specifications should I look for? Are there standard values or types of capacitors that work best for most DC motors?

Admin Admin 10/07/2024 4:57 am

@TechSpark No particular spec as far as I know. But the cap value, anywhere between 0.1 µF to 0.47 µF should work