480v high leg motor issue

journeyman0217 said:
So is there such thing as a 480v delta high leg? If so, what would be your voltages?
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It is certainly possible to have 480V delta high leg.

You would need a transformer that provides a 480V delta, and one of the 480V coils would have a mid point tap. The midpoint tap would get grounded. If you set this transformer up this way, you would have 480V L-L for all 3 phases, and L-G voltages of 240V, 240V, and 416V.

There is a good diagram midway down this page: https://ctlsys.com/support/four_wire_delta_circuits/
 
journeyman0217 said:
Nobody could ever tell me what they were, thank you
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You are most welcome.

Here is a very typical nameplate from a common Delta -> Wye step down transformer, you can see the 2 dashed lines on the primary and secondary showing a 30 degree phase shift between them. The dotted line on the Delta Primary is "angled" up 30 degrees and the dotted line of the Wye Secondary (at X0) is straight across with zero "angle"

1755097031563.png

Your Delta to Delta coil setups are straightforward and as the current rises in any one primary coil, it does so at the same time in its secondary mate. So zero phase shift and the dotted lines in your nameplate at H1 and X1 show the same angle - with no shift between them.

This phase shift is mostly a nerdy thing and it is very common for them to get misinterpreted as some kind of grounding indications. But they are not, it's science yo ! ;)

Also, sorry this thread is sliding off the rails into the transformer weeds - I assume your motor problem is not related to your transformer.

Again - good luck!
 
MD Automation said:
You are most welcome.

Here is a very typical nameplate from a common Delta -> Wye step down transformer, you can see the 2 dashed lines on the primary and secondary showing a 30 degree phase shift between them. The dotted line on the Delta Primary is "angled" up 30 degrees and the dotted line of the Wye Secondary (at X0) is straight across with zero "angle"

View attachment 2579091

Your Delta to Delta coil setups are straightforward and as the current rises in any one primary coil, it does so at the same time in its secondary mate. So zero phase shift and the dotted lines in your nameplate at H1 and X1 show the same angle - with no shift between them.

This phase shift is mostly a nerdy thing and it is very common for them to get misinterpreted as some kind of grounding indications. But they are not, it's science yo ! ;)

Also, sorry this thread is sliding off the rails into the transformer weeds - I assume your motor problem is not related to your transformer.

Again - good luck!
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This is awesome…completely makes sense to me now. Thank you for taking the time to explain. Definitely didn’t derail because I’m understanding now what the overall scenario I have going on is. Just an update it seems as if the control coil to the contact is bad and not providing the necessary voltage to fully engage the contact, therefore closing our “low voltage” relay.
 
jim dungar said:
Not every transformer should be run backwards. As previously mentioned taps are an issue. Some small transformers, like machine tool units less than 3kVA may actually have compensating windings on their primary to account for losses in thier cheaper core construction. Finally there is the probability the increased inrush/energizing current may require primary side OCPD which exceeds the NEC limits.

[Soapbox]
The reality is the NEC has their restriction, for manufacturer approval, because too many installers do not follow manufacturers instructions, especially when they are not included with the equipment. This is similar to how SCCR requirements have been added to article 240, in addition to the historical ones in 110.9 and 110.10, or the specific prohibition of 2 grounded conductors I a termination that accepts 2 grounding conductors.[/soapbox]
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How many machines such as overhead cranes are both motors and generators depending on what they are doing? Although unusual I have put up 480 volt bridge cranes in buildings fed by 208 or 240 volt services and had to install a step up transformer.
 
Joethemechanic said:
How many machines such as overhead cranes are both motors and generators depending on what they are doing?
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In these cases the generation caused backfeed is for short duration and is occurring on an already energized transformer. Voltage regulation is also not an issue.
 
Joethemechanic said:
How many machines such as overhead cranes are both motors and generators depending on what they are doing? Although unusual I have put up 480 volt bridge cranes in buildings fed by 208 or 240 volt services and had to install a step up transformer.
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This point comes up in discussion of transformers for PV systems. The fact is that all transformer action is bidirectional. Power can flow in either direction and the transformer will work just fine.

IMHO the distinction between primary and secondary has more to do with which side gets energized first or which side 'defines' the voltage of the whole setup.

In the case of regenerating induction motors or line interactive PV inverters and the like, the transformer gets energized from the utility side. The utility is defining the voltage of the whole system. But then the power flows _two_ the utility. IMHO in this situation the primary side is the utility side even though power is flowing to the utility.

-Jonathan
 
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