rtac/rtaa

[socotech]

can you test a screw with a megger? another tech in my company claimes he checked a compressor that was throwing the breaker with a megger against a compressor that was working ok and got the same readings.???????

[zw17]

You can check any motor windings with a megger.

What makes you think he's lying?

[milkyway]

dont meg in a vac., and dont over voltage the meg tool with the applied voltage .,

example: 208 motor
meg with 208 not 600 volt

[R123]

and dont over voltage the meg tool with the applied voltage .,

example: 208 motor
meg with 208 not 600 volt

What??????

Can you please enlighten us on this????

[Nuclrchiller]

The same rules apply as to any other motor. But with an RTAC you will probably see lower readings than you would expect. I suspect that has more to do with the POE oil than it does with the motor.

[henpeck]

Yes you can and what were the megger readings???? Was the one tripping the breaker grounded, or pulling LRA?


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[always looking]

You can get a bad meg reading on a good rtaa screw compressor. If the compressor has the old style terminals and is rusty under the motor terminals insulators. I have had them go as low a .5 megaohms.

[milkyway]

What??????

Can you please enlighten us on this????

Well I can try, haha
I know for a fact that not supposed to meg n a vac
As far as my example : we'll that may be wrong example.,
Guess what I was trying to say was if you compressor motor volt rating is 600 volt, not supposed to meg at a higher voltage., am I correct in typing this??

[Entropie]

It`s not the voltage that kills a motor. It`s always the current. I haven`t seen an compressor motor killed by megging him. But most compressor manufacturers recommend not to megger with a system in deep vacuum.

[R123]

Well I can try, haha
I know for a fact that not supposed to meg n a vac
As far as my example : we'll that may be wrong example.,
Guess what I was trying to say was if you compressor motor volt rating is 600 volt, not supposed to meg at a higher voltage., am I correct in typing this??

You are correct that you are not supposed to meg in a DEEP vacuum but I've never heard about not to meg at a higher voltage. As a matter of fact, my megged doesn't go below 500 volts and I meg 230 volt motors all the time.

[R123]

Mlk, after researching this, you are right about not to meg at a much higher voltage than the voltage rating of the motor.

[supertek65]

you should set the voltage at twice the rated voltage,
I almost exclusively work on 480 stuff
i always meg at 1000 volts.

Mlk, after researching this, you are right about not to meg at a much higher voltage than the voltage rating of the motor.

[jayguy]

you should set the voltage at twice the rated voltage,
I almost exclusively work on 480 stuff
i always meg at 1000 volts.

i meg everything at 1000 VDC...even 115 VAC motors...no problems. i have also megged motors in 500 micron vacuums without issue...my megger tops out at 0.002 ADC...not gonna hurt anything.

applying line voltage to a motor in a deep vacuum...now that's a youtube video I want to see!

[supertek65]

LOL!!!!!!!!!!!!!

i will post it

i meg everything at 1000 VDC...even 115 VAC motors...no problems. i have also megged motors in 500 micron vacuums without issue...my megger tops out at 0.002 ADC...not gonna hurt anything.

applying line voltage to a motor in a deep vacuum...now that's a youtube video I want to see!

[maxster]

the winding sensor short out if megged in a vac,also for what a CCH on the screws is even with Yorks Hellicals. if they are stone cold you will read a shorted winding to ground,and have had then tripped the unit mounted breakers during winters.