Transformer help!!

[T.M.Haja Sahib]

Please explain how there can be current when no load has been placed on the transformer??????????????

Surely,there can be no current,when there is no load on the transformer.If the 120V loads on the 120V/240V single phase transformer are not balanced,the voltages across them would also be unbalanced,should the neutral be broken.The OP reported that the voltages normalized on connection of X2 X3 to the ground.It means that in addition to broken neutral,there might be ground fault of neutral wire also.This could easily be ascertained by checking the current in neutral-ground connection.

 

[don_resqcapt19]

Surely,there can be no current,when there is no load on the transformer.If the 120V loads on the 120V/240V single phase transformer are not balanced,the voltages across them would also be unbalanced,should the neutral be broken.The OP reported that the voltages normalized on connection of X2 X3 to the ground.It means that in addition to broken neutral,there might be ground fault of neutral wire also.This could easily be ascertained by checking the current in neutral-ground connection.

Read the posts, the system was never put into service and the voltages were the result of an open bonding connection.

 

[T.M.Haja Sahib]

..... the voltages were the result of an open bonding connection.

With due respect I want to submit,''It can't be.The OP might have misled. ''

 

[Besoeker]

With due respect I want to submit,''It can't be.The OP might have misled. ''

With all the respect deserved, might I suggest that you read what was written rather than making up your own version of events?

 

[don_resqcapt19]

With due respect I want to submit,''It can't be.The OP might have misled. ''

It can't be? A missing or open bonding connection cannot cause those voltages?????????????????????

 

[T.M.Haja Sahib]

It can't be? A missing or open bonding connection cannot cause those voltages?????????????????????

Here my point is disconnection of X2 X3 from ground would not result in unequal voltages to ground,unless there is insulation breakdown of any one phase conductors.

Here is an example.There exist, in addition to solidly grounded neutral 3 phase power supply systems,isolated neutral 3 phase power supply systems.As long as long there is no insulation breakdown of any one phase conductors,the voltages remain equal with respect to ground.The same applies in the present case.

 

[iwire]

Here my point is disconnection of X2 X3 from ground would not result in unequal voltages to ground,

Of course it could even without insulation break down.

 

[T.M.Haja Sahib]

Of course it could even without insulation break down.

I gave an example to support my claim.

What about yours? ( Do not state the OP's case as your example.It can not be accepted....... ).

 

[iwire]

I gave an example to support my claim.

What about yours? ( Do not state the OP's case as your example.It can not be accepted....... ).

Without any intentional connection to 'ground' the measured voltages from line to ground will be due to capacitance coupling of circuit conductors to ground. Unless the capacitance was the same on both lines the readings will be different.

 

[T.M.Haja Sahib]

Without any intentional connection to 'ground' the measured voltages from line to ground will be due to capacitance coupling of circuit conductors to ground. Unless the capacitance was the same on both lines the readings will be different.

See the voltages to ground as stated by the OP

.......... My issue is ...... I have ........ 130v from X1 to ground, but only 50 volts X4 to ground.........

the unequal capacitances between lines to ground can not vary this much........

 

[Besoeker]

I gave an example to support my claim.

Your claim is without basis.

From post #9:

If no part of the secondary is grounded there is no ground reference for the voltage measurements wrt ground. They are therefore indeterminate.
It's a simple concept. Or ought to be.

 

[iwire]

See the voltages to ground as stated by the OP

the unequal capacitances between lines to ground can not vary this much........

You don't get out in the real world much do you?

 

[T.M.Haja Sahib]

You don't get out in the real world much do you?

You are not giving an example to support your stand either.

 

[T.M.Haja Sahib]

You are not giving an example to support your stand either.

You can't.Because if you are right,then isolated neutral power supply systems can not exist,because of large unbalanced voltages at the load end even when there is no insulation breakdown.........

 

[Besoeker]

You can't.Because if you are right,then isolated neutral power supply systems can not exist,because of large unbalanced voltages at the load end even when there is no insulation breakdown.........

You seem to be completely misunderstanding the point. The unbalanced voltages measured were to GROUND. Not across the transformer windings nor the load.

And at the risk of repeating the same point ad nauseum, if no part of the winding is connected to ground, voltage measurements to ground are indeterminate. The very act of connecting a voltmeter from one end of an isolated winding to ground will itself change potentials. If you can't measure the voltage without changing it, you can't determine what it actually is.
Thus indeterminate. Same with your completely isolated hypothetical three phase system.

 

[Besoeker]

I gave an example to support my claim.

It doesn't.

 

[topgone]

You seem to be completely misunderstanding the point. The unbalanced voltages measured were to GROUND. Not across the transformer windings nor the load.

And at the risk of repeating the same point ad nauseum, if no part of the winding is connected to ground, voltage measurements to ground are indeterminate. The very act of connecting a voltmeter from one end of an isolated winding to ground will itself change potentials. If you can't measure the voltage without changing it, you can't determine what it actually is.
Thus indeterminate. Same with your completely isolated hypothetical three phase system.

This is a correct assessment, IMHO. You don't get a definite reading to ground when the measured quantities don't have any part of the source is "grounded".

 

[Besoeker]

This is a correct assessment, IMHO. You don't get a definite reading to ground when the measured quantities don't have any part of the source is "grounded".

Yes. Common sense.
Maybe common sense isn't as common as it's purported to be.

 

[T.M.Haja Sahib]

This is a correct assessment, IMHO. You don't get a definite reading to ground when the measured quantities don't have any part of the source is "grounded".

Even in an isolated neutral three phase system the neutral is unintentionally grounded through capacitive coupling.So there exist a definite phase to ground voltage in this case also.............

 

[Besoeker]

Even in an isolated neutral three phase system the neutral is unintentionally grounded through capacitive coupling.So there exist a definite phase to ground voltage in this case also.............

C'mon. You must know that simply doesn't hold water.