Transformer Voltage

ah, I can answer you from theory. somebody may answer you in practice.

I dont think there is any problem. there is a tolerence allowance in transfermer design, or say flux in the core. for example, 1.4T can be designed as 1.2 T. or 1.8T as 1.6T.

however, in this time, the currrent will be a bitter large than ususal.

the outpurt voltage will be (480/440) x 220 = *V.

winding will not be affected, but pay attation to sink heat.

generally speaking transformer has +-20% allowance voltage ripple.

You have to check the specs of the transformer as it permits +/- range in its input voltage.about the output voltage you can adjust the transformer taps and still get the output you require.

Approx 9% above means that if you have tappings i.e normally transformers will have 2% X 5 tappings( steps) if that is so with your transformer than you will need to adjust tha tappings to the lowest one .

Note: adjust tappings with power disconnected.

Good luck!

There's a couple of questions you need to answer to determine if you can do this and you still may need to consult your system engineer.

Is this transformer the only thing this generator is connected to? If it is then just lower the gen voltage. If the generator is servicing other 480Y/277v loads then you may have some difficulty. You'll need to be aware that you'll have higher than normal potentials when on the generator. Should be 240/138 on the secondary of your transformer. Depending on your loads this could be a bit hot.

Also verify your generator neutral connection. Probably should not be bonded to ground at the generator but at your main service.

As you are planning to use it for 480V in place of 440 V if you are using lowest tappings you will get some volage more than 220V at output (about 240V)

V1/ V2 = N2/ N1 as N2/ N1 is const as V1 will increase V2 will also increase. Check for your output volatage requirement tolarance. In your case V2 will be arout 240V.

Are you planning to use it on full load?

If you use it for full load them more heat will be genrated and then may cause some trouble.

If you do not need to use it at full load ( full Amp spec) and 240V is acceptable, put a braker on the output side of transfromer with ratings less than the rated current of the tranformer at 240V and little more than your demand current. (Note that rated current at 240V will be less than that of for 220V).

V1I1 = V2I2

V1 = 440V I1 = Rated input current (250KVA / 440V = 569A)

V2 = 220V I2 = 440 x 569 / 220 = 1138 A

when V2 = 240 I2 = 440 x 569 / 240 = 1041A

or I2 = KVA / V2 = 250K / 240 = 1041 A

Rated current at 240 V is 1041 Amp so put breaker with setting for current Less than 1041 Amp and little more than your demand 10% (say demand is 900A put breker settings for 900 + 10% of 900 = 909A)

In this case transformer will never get hated to it's therman ratings.

Do validate the calculations and formule before practically conneting things.

Good Luck.

Thanks,

Makarand

I agree with the above as far as the tap settings, try that first. If the tap settings do not get you where you must be (some piece of equipment is voltage sensitive), you might consider a buck-boost transformer set up. I have used them on single voltage motors, to get 230 when 208 was the only available voltage. They are small and inexpensive, but make sure they are connected correctly and the loads are balanced. If not the neutral can carry too much current and eventually overheat. You should probably check the major loads and make sure the voltage variation will not be detrimental or even destructive. In the US we try for +/- 5% on a 120 V base. That would be 114 to 126 VAC. Motor operation outside nameplate voltages will affect the starting and running characteristics. If there are resistance heaters or incandescent lights, probably no big deal. Some of the ballast assisted fixtures might suffer from high or low voltage. Effects can range from overheating to an irritating flicker.

Welcome to engineering!