240vac

[rkalstad54]

checking power on a mori lathe and getting 245 on a and c phases and o on the b phase to ground checked it back to the buss and its the same didnt find any fuses blown and machine wont power up.

 

[augie47]

What is your phase to phase voltage ? (The 0 to ground is "normal" on a corner grounded delta system..not real common but likely in your case).. no input on why...might be time for an electrical contractor

 

[don_resqcapt19]

Sounds like a grounded phase system. What are the line to line voltages? A to B, B to C, and A to C

 

[hillbilly1]

Most likely a problem in the control circuit.

 

[rkalstad54]

What is your phase to phase voltage ? (The 0 to ground is "normal" on a corner grounded delta system..not real common but likely in your case).. no input on why...might be time for an electrical contractor

245 phase to phase it had me confused never seen that before and i already changed the power supply for the spindle amp and a 24vdc power supply as well .

 

[augie47]

Sounds like you have a grounded delta 240v system (either intentionally grounded or an 'ungounded' system where one phase has become grounded)..
You might confirm the type system with your power supplier and if it is "ungrounded" or "corner grounded" run that info by the machine supplier. Some equipment will not 'play nice' with those systems.

 

[hillbilly1]

Is this a new install? Or existing? If new, the machine may have a phase loss/phase reversal relay that’s got it locked out. If it’s an existing install, is 24 volts leaving the E-Stop? Could be a faulty or not engaged safety interlock somewhere too.

 

[rkalstad54]

Sounds like you have a grounded delta 240v system (either intentionally grounded or an 'ungounded' system where one phase has become grounded)..
You might confirm the type system with your power supplier and if it is "ungrounded" or "corner grounded" run that info by the machine supplier. Some equipment will not 'play nice' with those systems.

thanks will do

 

[infinity]

What colors are the conductors? A corner grounded system should have one conductor identified as the grounded conductor.

 

[don_resqcapt19]

What colors are the conductors? A corner grounded system should have one conductor identified as the grounded conductor.

While that is a code requirement, I have never seen that in the field with any of the corner grounded systems I have worked on.

 

[infinity]

While that is a code requirement, I have never seen that in the field with any of the corner grounded systems I have worked on.

Me too. We typically see this in reverse wired Delta/Wye transformers which are corner grounded with 3 fuses in the fused disconnects.

 

[rkalstad54]

Is this a new install? Or existing? If new, the machine may have a phase loss/phase reversal relay that’s got it locked out. If it’s an existing install, is 24 volts leaving the E-Stop? Could be a faulty or not engaged safety interlock somewhere too.

no i just started here but theyre telling me machine was in production for a year or so.

 

[gar]

230517-1653 EDT

rkalstad54:

Specifically where are you located? In DTE areas of small business there are many locations with wild leg deltas being fed from two transformers.

These usually have one transformer with a center tapped secondary with the center tap grounded to supply single phase loads, 120-0-120 V. Then there is a second transformer providing the third phase.

.

 

[gar]

230519-1703 EDT

rkalstad54:

To add to my previous comment.

My son has a machine shop. This is supplied from a two transformer wild leg source. He has a 200 A 240 V source main panel.

On this supply he has 5 20 HP CNC lathes, 2 20 A CNC lathes, welding, a 20 HP belt sander, MIG welder, air conditioners, lights, and office equipment. The potential total is over 200 A per phase. No prolem running the shop. Has never blown the main breaker in over 20 years.

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