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Voltage/Current Noise

BSMechEng

New Member
Does noise (current or voltage) affect operation of a motor? I would assume so, to some extent, but my guess is that it is pretty small. Maybe it reduces motor efficiency by <5%?
 

whit3rd

New Member
The windings of a motor are a big filter inductor, as is the mass of the rotating parts. So, noise really doesn't enter a motor from the electric supply in any significant amount. Most
of the spectrum of a noise source is just too high frequency to affect motor parts.

Brush-type motors have intermittent electrical contacts, that can cause noise on their
power inputs, or even radio static.
 

BSMechEng

New Member
Thank you for your response. My question comes from having seen a device advertised that is supposed to reduce the amount of electricity required to operate appliances. In my mind, most appliances are essentially motors (compressors, blenders, microwave ovens, etc.). The reduction is due to eliminating noise. The claimed increase in efficiency is up to 90%, which I don't believe. The noise is purportedly eliminated by filtering noise out of the sine wave. But I don't think the motor is significantly affected by noise on the supplied voltage. Does this seem reasonable?
 

Visitor

Well-Known Member
It may help reduce power factor (V × A as opposed to watts). But generally, consumers are billed for watts used, irrespective of V × A, so it wouldn't reduce bills for most consumers.

The place this may make a difference to some people is if you are using a DC inverter to supply an AC load like a motor. In that case, you have to supply V × A. If the power factor is 0.5, you're generating twice the power than if the power factor was 1.

Found this out running a ¼ HP furnace motor from an inverter - it required way more power than expected.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
My question comes from having seen a device advertised that is supposed to reduce the amount of electricity required to operate appliances.
They are often just a small capacitor in a box, usually with lights to "show they are working".
Total scam, as Jim says.

Big Clive on youtube has done some serious analysis of such gadgets, with details of the effect they have (if any).
In reality they are as likely to increase running costs as decrease, and the effect is minuscule if it has any effect at all.

 

unclejed613

Well-Known Member
Most Helpful Member
The noise is purportedly eliminated by filtering noise out of the sine wave. But I don't think the motor is significantly affected by noise on the supplied voltage. Does this seem reasonable?
if it's one of the devices i'm thinking of, no they do almost nothing at all except add an additional few milliamps to your house's average current draw...
 

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