TRANSFORMERS

[dououie]

I had a call today and found that it was the secondary side of the transformer, had no voltage. My question is, Is there another way besides knowing no power is coming off to check if the transformer(primary or secondary)is damaged or blown.The Xfrm was a Marcus mct50.
600 volt primary, and 120/240 volt secondary. Some info on this would be great. Thanks. If anyone worked in the toronto area today, hope you kept warm.lol.

[fixerup]

Ohm it out it should have high resistance.No resistance it is bad.If you have a new replacement, ohm it out and record it for future reference.

[maxster]

i have seen secondary shorts blow the primary screw in fuses on Trane rooftops,and never screw in the primary line fuses for a TR like that with the power up.the draw will blow the fuse and it will be the 2nd one you put in that ruins your day.

[caosesvida]

a transformer is just two coils of wire, primary and secondary, just like the windings of a motor (more or less). to troubleshoot them (as stated in thread) You would do a continuity and resistance, and if you have one megger also. Either the wire is good or bad. As far as what resistance you should get, you could check an identical one or call the manufacturer.

[sigma]

Originally posted by dououie
I had a call today and found that it was the secondary side of the transformer, had no voltage.

My question is:
Did you check primary for presence of 600V?

[john dalton]

Dear Dououie,

Simple step down transformers, such as the one you’ve referenced, need to be replaced because of one of the following reasons:

1. Open primary circuit: (resistant check shows infinite reading when checked or open when continuity is checked across the primary leads).

2. Open secondary circuit: (resistant check shows infinite reading when checked or open when continuity is checked across the secondary leads).

3. Grounded primary circuit: (resistant check shows under 10,000 ohm reading when checked from either lead of primary to ground or closed when continuity is checked from either lead of primary to ground).

4. Grounded secondary circuit: (resistant check shows under 10,000 ohm reading when checked from either lead of secondary to ground or closed when continuity is checked from either lead of secondary to ground).

5. Shorted primary circuit: (resistant check shows reading higher than 10% or lower than 10% of the factory resistant reading across the primary leads).

6. Shorted secondary circuit: (resistant check shows reading higher than 10% or lower than 10% of the factory resistant reading across the secondary leads).

7. Mechanical problem such as transformer fluid leaking out of housing, burned areas of the transformer housing, primary or secondary insulation cracking or missing from leads, heavy burnt “cigar odor” coming from winding area(indicating weak or failed coil circuit insulation), and/or any other out of the ordinary observation you might make regarding the visual, feel, or smell aspects of your check.

Hopefully this will be of some valve to you.

Respectfully Submitted,
John J. Dalton





[Edited by john dalton on 01-20-2005 at 10:31 AM]

[dououie]

THANK YOU VERY MUCH FOR ALL OF YOUR HELP, KNOW I HAVE A BETTER IDEA WHEN I AM LOOKING AT ONE, I DON'T JUST LIKE TO FIND WHAT'S WRONG WITH IT, I'D RATHER FIND WHAT THEN WHY. SO AGAIN THANKS GUYS.

[dououie]

SIGMA

YES, I CHECKED THE VOLTAGE ON THE PRIMARY AND HAD 600V, DID NOT HAVE ANY SECONDARY VOLTAGE, I KNEW IT WAS NO GOOD, BUT FOR MY OWN REFERENCE WANTED TO FIND OUT HOW ELSE TO CHECK IT. THANKS

[chico-cool]

Many transformers have a safety swith,,, Is this the case?? because they open the circuit if there is overcurrent on it...