Is there a difference between 400/100 and 400:1.73/100:1.73 transformers??
- Thread starter Kaaud
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I, for one, don't recognize those ratios as transformer designations. I could make educated guesses, but, can you tell us more about them? Actual voltage ratings and winding configurations?
rcwilson
Senior Member
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- Redmond, WA
IEC voltage transformers may have a line-neutral rating listed as (Volts phase-phase)/ (sqroot 3). Instead of a 277V winding it would be listed as 480/ Sqroot3 or 480/1.73.
The two ratios you listed are the same.
In the ANSI world VT's are often supplied with a 120V/69.3V secondary to feed protective relays or meters. The 120V tap is for devices that need 120V phase-to-neutral. The 69.3 volt tap is for devices that need 120V phase-phase. The 100/1.73 rating would be for supplying the IEC standard secondary voltage of 100V phase to phase in a wye connected VT bank.
The two ratios you listed are the same.
In the ANSI world VT's are often supplied with a 120V/69.3V secondary to feed protective relays or meters. The 120V tap is for devices that need 120V phase-to-neutral. The 69.3 volt tap is for devices that need 120V phase-phase. The 100/1.73 rating would be for supplying the IEC standard secondary voltage of 100V phase to phase in a wye connected VT bank.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
In other words, they took something simple and made it more complicated. Gee. 
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