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Is Their Any Motor That Has Zero Back EMF?

10/14/2014 5:33 AM

1. I just want to ask that is their any motor that has zero back emf or can we get/make zero back emf from any motor ?

2. What will be the effect on the motor operation if their is zero back emf ?

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#1

Re: Is their any motor that has zero back emf?

10/14/2014 7:16 AM

1. No

2. Vastly increased efficiency, but see #1

Del

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#2

Re: Is Their Any Motor That Has Zero Back EMF?

10/14/2014 8:30 AM

if the windings are open there will b no back EMF. or rotation

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#3

Re: Is Their Any Motor That Has Zero Back EMF?

10/14/2014 8:48 AM

A shunt wound motor can have 0 back EMF. Once the motor is running, open the field windings. B4 doing this verify your life, disability, and unemployment insurance policies are current. As I've mentioned in previous posts " bad 'tings gonna hoppen mon"

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#4

Re: Is Their Any Motor That Has Zero Back EMF?

10/14/2014 8:50 AM

Yes. See air motors.

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#5
In reply to #4

Re: Is Their Any Motor That Has Zero Back EMF?

10/14/2014 9:46 AM

Ah but the motor that drives the compressor that drives.... oh you get it...

Del

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#6

Re: Is Their Any Motor That Has Zero Back EMF?

10/14/2014 12:49 PM

Internal combustion.

Then there is this:

No EMF, but you will have other things to contend with out the back.

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#7

Re: Is Their Any Motor That Has Zero Back EMF?

10/14/2014 2:47 PM

I believe a piezoelectric motor does not produce a back EMF. However these little motors are best suited for very small motions.

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#8

Re: Is Their Any Motor That Has Zero Back EMF?

10/14/2014 5:44 PM

Motor;

Motor;

Motor;

Motor;

Motor;

Motor(s);

Motor;

Motor;

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#9

Re: Is Their Any Motor That Has Zero Back EMF?

10/14/2014 11:44 PM

Why would you want a motor having no back EMF?

As back EMF in a motor is caused by the motor *also* acting as generator (at the same time it is 'being a motor') one way to eliminate back EMF is to lock the rotor so that it does not move. No motion --> no generation --> no back EMF. But what typically happens when you lock the rotor? Your motor's current goes way up. Do it for long enough and your motor burns up.

You've probably noticed the lights dim momentarily when an AC motor starts, say, your refrigerator's motor. Why do they dim only when the motor starts but not when it's running?

They dim because there is initially no back EMF to oppose the current. It's only when the rotor is turning that the current drops. In fact, without back emf most motors would probably overheat and burn up in a very short time.

So you see, it's not necessarily a bad thing as some have suggested. It's actually quite a good thing and it has practical uses beyond keeping motors from drawing excessive current. Because back EMF is a function of rotor speed, one common use of back EMF is to use it to infer the speed of a motor without the need for a tachometer.

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#10

Re: Is Their Any Motor That Has Zero Back EMF?

10/15/2014 1:59 AM

If it was possible, then running current (up to a possible 8 x of normal running current with a normal 3 phase induction motor) would be the same as starting/stalled rotor current!!

As no back emf to cut current! Overheating/Fire/melting!

Why would you want to do this.....?

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#11

Re: Is Their Any Motor That Has Zero Back EMF?

10/15/2014 10:34 AM

A couple of years ago when I retired I was interested in this problem and found a solution in the form of solenoid pulse motor form by modifying shape of solenoid core. I thought I might have stumbled on to patentable material. Nope already done, already patented. Another engineer beat me to it. Even put a video on the internet. I found it with a search for "electric motor secrets" The effect is higher efficiency. Building a motor in the form of dual rotary solenoid with shaped core also works. I wonder how long it will be for a major manufacturer to pick up development?

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