Using transformer with 10% higher input voltage

[Jester]

Thoughts at using this transformer with 240V in at 220V terminal, and ~220V out at 200V terminal. Concern is over-excitation

Load is intermittent perhaps 20% duty cycle max. but will be near 1kVA at times.

[Zero999]

It should be fine, especially given the low duty cycle.

Did you get it from Europe i.e. a 50Hz region? If so, then it's even better, since the slightly higher frequency will reduce the flux, reducing the chance of saturation.

[BrokenYugo]

Japanese name and voltages make me think this is some sort of old boost transformer for using 220V (now 240) equipment on Japanese 200V power or vice versa, half of Japan is 50Hz so I wouldn't doubt it if it's happy on 240V 60Hz power. I'm no transformer expert but I would think checking the idle current at 240V would give a good idea.  EDIT: idle power, not current.

[johansen]

What are you worried about?

It will just warm up quicker.

Idle current is meaningless, you need a watt meter. or just weigh it, then put it in a well insulated box, leave it on for 1000 seconds (to make the math easier) and measure the temperature rise.