Grounded L1 leg?
Grounded L1 leg?
(OP)
Ok here it goes we have a 3 phase machine that uses 4 three phase motors and one single phase motor there was a short in the receptacle that caused a phase to ground short after replacing the receptecle I megged the motors and checked each power phase from the contactor to ground I had a zero reading with a vom from L1 to machine ground this machine is using one leg L1 and ground to supply the single phase motor the power circuit for the single phase motor goes through a relay circuit not a contactor the only way the ground to L1 clears is if I disconnect the power feed wire for the 120Vac circuit from the L1 leg disconnecting the single phase motor makes no difference so I am wondering if this is normal why when i had the single phase motor electrically disconnected and the relay block for this motor power feed circuit removed from the enclosure but electrically connected i had a 15 meg reading L1 to ground. keepin mind this machine is a birds nest and there is now documentation on the wiring and controls.





RE: Grounded L1 leg?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Grounded L1 leg?
RE: Grounded L1 leg?
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Grounded L1 leg?
jcromwell; Please copy your question out add some periods "." and some CAPITALS and plaster it back in here. We really do want to help, we just aren't into masochism. (Well Skogs might be..)
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Grounded L1 leg?
Help
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Grounded L1 leg?
RE: Grounded L1 leg?
Hope this is better my apoligies.
RE: Grounded L1 leg?
Many normal AC loads will appear to be a short circuit when measured with a VOM. It is an instance of the difference between resistance and impedance. The VOM measures resistance but the impedance limits the current in an AC circuit.
The impedance is typically many times greater than the resistance at 60 Hz. Is the machine blowing the feed breaker after the repair? What is the current draw of L1 with the motor and relay connected but nothing running?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Grounded L1 leg?
RE: Grounded L1 leg?
As was mentioned any load like a lamp or a relay coil can appear to have nearly zero resistance with a meter (using DC).
Can you measure the from the "power feed wire" to case ground with your meter set to a very low range? So we can see the actual low resistance? Is it 1.3 Ohms? 0.4 Ohms? 10 Ohms? What exactly are you getting?
If you can tell us 2 or 3 ohms, or more, we can suspect it is a load. If it is less, than likely it is an unintentional short.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Grounded L1 leg?
RE: Grounded L1 leg?
I hope you can take the time to make sure that machine is safe. Sounds a bit sketchy.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Grounded L1 leg?
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Grounded L1 leg?
I have rectified several dangerous situations and will continue to do so as budget and time permits. This process will take a little while but I believe management sees the overall value. Thanks for the insight.
RE: Grounded L1 leg?
Happy hunting.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com