A 10KVA-rated step-up isolation transformer is used to connect a 480v-delta
resistive heater to 208v-Y supply.

Measured currents are:
- primary (208v) current ~35A.
- secondary (480v) current ~15A

If my math is correct this transformer is undersized by 20 percent, or so: - primary: 35A x sqrt(3) x 208v = 12.6KVA - secondary: 15A x sqrt(3) x 480v = 12.3KVA

All wires and the breaker are sized to handle the measured currents. While the windings seem quite cool, the laminations are uncomfortably warm to the touch.

The load is turned on for periods of up to 15 minutes at a time and disconnected for between 10 minutes to overnight, depending on the demand for the equipment.

There doesn't seem to be evidence of over-temperature in the windings and wires are sized properly. Is there a risk here?

Thanks.

Measured currents are:

If my math is correct this transformer is undersized by 20 percent, or so: - primary: 35A x sqrt(3) x 208v = 12.6KVA - secondary: 15A x sqrt(3) x 480v = 12.3KVA

All wires and the breaker are sized to handle the measured currents. While the windings seem quite cool, the laminations are uncomfortably warm to the touch.

The load is turned on for periods of up to 15 minutes at a time and disconnected for between 10 minutes to overnight, depending on the demand for the equipment.

There doesn't seem to be evidence of over-temperature in the windings and wires are sized properly. Is there a risk here?

Thanks.