plate transformer

[scottdarling1221]

I have a plate transformer with a 220 primary tap but i have over 240 coming from the wall.
Its a stacked lamination style transformer made in the 80s.Can i run 240 on the 220 tap.

I wont be saturating the core

[KE6DF]

You should be OK. Most older 115 volt transformers run OK on the 120V+ most outlets have these days.

Also a transformer built in the '80 is relatively new compared to the 70 year old transformers many people run.

If you have a high current filament transformer that will run on 220 you could use it as a bucking transformer. Or two identical 115v filament transformers...

But I bet you will be OK without it -- especially since you are using it way under capacity.

[WD5JKO]

I wont be saturating the core

Just applying primary voltage can saturate any transformer. The primary volts for a given mains frequency, and number of turns around the core can only accept so many volts per turn before the primary excitation current ramps up extremely quickly. This has nothing to do with the VA rating of the transformer. I know you got a mule of a transformer. You need a way to crank up the primary voltage (0-240+) while looking at primary current. The excitation should be low and rise almost linearly until the core begins saturating. At this point the slope changes very quickly, primary current rises real fast, and the transformer may start buzzing.

Jim
WD5JKO

[KM1H]

In the 80's 230V was the norm but a lot of manufacturers called it all 220V because thats what people were used to for decades.

Ive yet to see any 220V plate xfmr even close to saturation at 240V but Id start being concerned at 245.

The many transformers Ive tested on the so called 110/115/117V or whatever you want to call it start to saturate at 123V especially for many Hallicrafter and others are happy at 125-130.

Carl
KM1H

[w4bfs]

Some of the the EF Johnson power transformers I have tested that are 110 V primary will start to run warm at 120 V with unloaded secondaries.  Connecting the 5 V fil winding in buck config cools it back off.  When I solid-state the power supplies of this type of rig I usually do this and it seems to help the transformers run cool (er).  Be sure to add appropriate fusing for each transformer to help protect dwindling sources of replacements.  73  John