Hi guys

Since its not possible to megger a solenoid, is it possible to use an LCR meter to measure the induction of the coil to see if it got a shorted winding ?

 

Inductance depends upon frequency.

LCR meters offer one or a few fixed frequencies. These may or may not be suitable.

a Q meter would be a better bet, since these are tunable.

 

What is the best method to run tests on solenoids ?

 

Who says you can't megger a solenoid?

 

Who says you can't megger a solenoid?

Correct me if i am wrong. I cant see how a megger test on a solenoid coil can be done

 

Playing interrogator; By shorted coil, I'm guessing you mean turns of the coil shorted to themselves, not to ground?

Say you connect your coil to an LCR meter, it spits out a number. Does this number mean anything to you? Do you have manufacturer specs for inductance, capacitance, resistance? I'm guessing not. So what do you do? You probably at least have manufacturer's spec for amps. So if it were me, I would energize it, and if it doesn't actuate, or if it actuates weakly despite being mechanically easy to operate, or if it draws other-than-nameplate amps despite being fully actuated, then I call it garbage.

 

Playing interrogator; By shorted coil, I'm guessing you mean turns of the coil shorted to themselves, not to ground?

Say you connect your coil to an LCR meter, it spits out a number. Does this number mean anything to you? Do you have manufacturer specs for inductance, capacitance, resistance? I'm guessing not. So what do you do? You probably at least have manufacturer's spec for amps. So if it were me, I would energize it, and if it doesn't actuate, or if it actuates weakly despite being mechanically easy to operate, or if it draws other-than-nameplate amps despite being fully actuated, then I call it garbage.

I fully agree with you, that is the method i use and have always used, but i was thinking that there has to be some other way to do this with all these test equipment we got today

 

Correct me if i am wrong. I cant see how a megger test on a solenoid coil can be done

Im assuming you're coming from the stand point of meggering motors, where you check for leakage between phases. That still doesnt check for shorted turns within the motor windings. The other part of meggering a motor is checking for leakage to ground, which can still be done on a solenoid. Just attach your probe to the armature and other probe to the coil leads.

 

i have limited exp when it comes to meggering, i am very interested in knowing how to check for shorted turns

enlighten me

 

The easiest way to check a solenoid would be by knowing what it's rated 'pull' is supposed to be. either in grams or ounces, and checking for this rating with weights or spring scales. Calculating inductance or magnetic field strength is complicated and as others have said, it is not easy to measure these attributes.

The attachment is from an old book and the entire book is available as a free pdf downloadable from google books. It basically shows how to calculate magnetic force from data such such as current, turns of wire, radius and length of coils. It is not an easy calculation, but some provided charts make such calculations easier.

 

I can tell you a few things that do not seem to work.

Expected a jump in current from an ac solenoid with a shorted turn.
It takes a large number of shorted turns in relation to the total turns to see a meaningful difference.

LCR meter changed only from 182mH to 180mH on a 120vac solenoid when shorting 5 turns.

Not very helpful.

Was not successful building a growler with the junk on my bench.
It may merit looking into. Not sure how a solenoid could be coupled for testing.

 

And a picture...................................................

 

Any resultant effect will also be different on an AC than a DC version.
Max.

 

How does the industrial electrician guys test motors and transformers with turn to turn shorts

 

AC motors, transformers, usually with a current test, both in an off load or open condition.
Max.

 

I can tell you a few things that do not seem to work.

Expected a jump in current from an ac solenoid with a shorted turn.
It takes a large number of shorted turns in relation to the total turns to see a meaningful difference.

LCR meter changed only from 182mH to 180mH on a 120vac solenoid when shorting 5 turns.

Not very helpful.

Was not successful building a growler with the junk on my bench.
It may merit looking into. Not sure how a solenoid could be coupled for testing.

How about DC coils with LCR meters

 

AC motors, transformers, usually with a current test, both in an off load or open condition.
Max.

You mean they apply a voltage and see if they get the current that its rated for ?

 

A forum search reveals that shorted turns is a popular subject here, for example

http://forum.allaboutcircuits.com/showthread.php?t=38273&highlight=shorted+turns&page=2

see also this website

http://www.repairfaq.org/sam/flytest.htm

 

You mean they apply a voltage and see if they get the current that its rated for ?

This is about the most practical for AC devices, also if a frequency is applied to a DC device and the inductance is known.
A shorted turn on an AC device will be much more self evident in operation.
Max.

 

How about DC coils with LCR meters

I believe it would be the same.
Only a high number of shorted turns would be measurable.

Ringing works.
It takes a different test for each coil.
And a scope or ring tester.

To test a transformer or motor that has more than one winding, energize a winding with a few volts dc.
A neon bulb across a winding will flash when power is removed and field collapses.

If a winding is loaded or shorted neon flash will be diminished.

This test should work with a single coil like a solenoid. It does not in my tests with an external shorted coil.

Seems it should! I may not be coupled close enough. Magnetics are one of my weak points.