Isolation transformers

hello,

i think may be some problem is there in isolation transformer because voltage between phase and ground is not equal to the neutral and ground.

so, please check once before doing any further work on it.

in isolation transformer voltage on secondary side is same as primary side voltage because isolation transformer is having a turns-ratio of 1:1 with ferrite core.

You must be off your rocker, . . . a power transformer using ferrite core!

That is a new one!

TOPAZ transformers are typically 120/120 or a 240/240 volt, . . . double shielded - to provide good isolation even at higher interference frequencies.

The degree of isolation you get - depends on your connections - proper connections!

Obviously, there is something abnormal. You have mentioned that you have measured 115V between phase and earth and also between earth and neutral. but also you have mentioned that earth is kept isolated from both phase and neutral. Where is the third phase. Is this a single phase transformer. What is the current condition of the equipment.

Pl. give complete details of the conserned equipment and problem, when you raise any issue via post in any forum,

Many 3Ph star connected VT transformers up to 11KV only fuse red and blue phases on the secondary. Yellow being a link solidly earthed.

As many here have already mentioned, there just isn't enough information here to do a proper diagnosis. I don't know why people then jump on the idea that your transformer must have a fault. If these conditions are true then there may not be a problem with your transformer. But this is not the only combination of conditions that will give the symptoms you've described with a good isolation transformer.

• The primary voltage being applied to your single phase transformer is 230VAC RMS.
• The instrument you are using to measure this voltage has a very high input impedance.
• The secondary windings has a lower insulation resistance to ground than the input impedance of the meter.
• Somewhere downstream of your transformer there is a device with a balanced lower impedance to ground than your test instrument.

I think the first two conditions given by you are TRUE. I have connected 230V ac supply to primary. I am using a Fluke multi-meter with very high input impedance. (I have to check the specs to give you the exact value). the other two conditions also may be true because of the high impedance of the fluke multi-meter.

How about this? It's a 3 phase 208V Wye (star) secondary, the Neutral is grounded, but at a different location than the EGC (as it should be). But there is a ground potential difference that just happens to make the Neutral to Ground reading 115V. For example it has a Neutral Grounding Resistor.

isolation xformer ph & neutral are grounded with ir value, so it gives voltage as you are measured. draw ground connection with ir value with your ph & neutal of isolation xformer & study drawing. then you will understand why you are getting voltages.