I need a transformer! 1

[crthompson]

I need a three phase 10VA, 1000V, step down transformer with either a 120V, 240V, 480V, or 600V secondary. I have been looking for hours with no luck... Does anyone know of a manufacturer off hand? All this transformer is going to feed is a small three phase voltage monitor... I can purchase these voltage monitors in 120v, 240v, 480v, and 600v models so any of these secondaries would be fine with me. Thanks in advance!

 

[ScottyUK]

Mining seem to like 1100V as a supply voltage so you might have some luck if you can identify a switchgear builder who does work for that industry.

An idea of your location would help - it's probably the US like everyone else who doesn't say, ha-ha - but if you're really stuck you might find (say) Baldwin & Francis in the UK would be prepared to sell you one or two as spares for their mining gear. You probably want 60Hz too, but at least the laws of physics are in your favour and you can likely run a 50Hz VT at 60Hz without major concerns.


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If we learn from our mistakes I'm getting a great education!

 

[crthompson]

Thanks Scotty! I actually work for a switchgear manufacturer that does work for the mining industry in the US... I was looking for this transformer to monitor the phases on a 1040V 3 phase feeder circuit... Not long after I made the post I found a manufacturer out of Italy called Fase and they have a single phase version of what I was looking for. I was thinking that if I can't find a three phase version that I might be able to connect two of them in an open-delta to achieve the same thing. I will look into Baldwin & Francis to see what kind of transformers they have... Thank you very much for your response!

 

[waross]

Use three 600 volt transformers in wye configuration. Each will see 577 Volts on a line to neutral circuit. That will give you 115 Volts on a 600:120 volt transformer, suitable for 115 Volt rated motors if you keep the lead resistance low.

Bill
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"Why not the best?"
Jimmy Carter

 

[davidbeach]

Bill, that works fine for a solidly grounded system, but if impedance grounded or, worse, ungrounded, the transformers when connected in wye must be rated for line-line voltage.

 

[waross]

Good point David, and good engineering. Thank you.
With a North American background I sometimes assume grounded wye systems.
As a kludge, and at that voltage, back in the day, we would consider the standard megger test of the time of twice working voltage plus one thousand Volts and give it a try. While not perfect, a balanced voltage and the onset of saturation will give some secondary voltage and phase angle stability. A delta connected secondary will give a level of stability related to the impedance of the transformers. (%Z x 3)

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[pwrengrds]

Why can't you buy 20/1 PT's and live with having nominal voltage of 50 volts, most meters should be able to handle it. They are standard off the shelf items. It would be rated 2400 volts nominal.

 

[crthompson]

All this transformer is going to feed is a small three phase voltage monitor... I will not be metering this circuit. I can purchase these voltage monitors in 120v, 240v, 480v, and 600v models so only these secondaries would work for me. This monitor detects undervoltage, phase loss, & phase sequence... The maximum load for the monitor is 6VA... I found an Itallian transformer manufacturer (Fase) that has a single phase version of what I need. I will have to bank 2 of them together as open-delta but I think they should do the trick! Just waiting on my quote to come back ... Thanks everyone!!