How to lower voltage on input of transformer

[philly]

We have a two winding single phase transformer that is rated 460V primary and 230V secondary in a control cabinet. Our distribution is 480V and this transformer was purchased incorrectly (European supplied cabinet) and is therefore providing a high voltage of about 260V on the secondary which is causing problems with controls and electronics.

Aside from the obvious answer of simply replacing the transformer I'm curious as to what other theoretical solutions exist.

The first one I can think of is finding a 20V buck boost transformer and wire it with the transformer to buck the voltage by 20V in order to supply the correct voltage on the secondary.

My second solution I dont know is possible, but can you install a reactor on one of the primary lines in order to drop the voltage across the reactor and thus present a lesser voltage at the primary of the transformer. The more I think about this solution the more I think it wont work, because the voltage drop across the reactor will be dependent on current in the primary which will change depending on the load on the secondary and therefore vary the voltage on the primary?

 

[gar]

100420-2255 EST

philly:

Buy a new transformer.

You could unwind turns from the secondary, but in your case that would not be satisfactory.

.

 

[Lcdrwalker]

Cost

Cost

There are several ways that you can lower the voltage although none of them would be safe. You have mentioned two of them and you are talking auto-transformer which is dependent on load. With the labor and safety I suggest an appropriate machine tool control transformer.

 

[zog]

We have a two winding single phase transformer that is rated 460V primary and 230V secondary in a control cabinet. Our distribution is 480V and this transformer was purchased incorrectly (European supplied cabinet) and is therefore providing a high voltage of about 260V on the secondary which is causing problems with controls and electronics.

Aside from the obvious answer of simply replacing the transformer I'm curious as to what other theoretical solutions exist.

The first one I can think of is finding a 20V buck boost transformer and wire it with the transformer to buck the voltage by 20V in order to supply the correct voltage on the secondary.

My second solution I dont know is possible, but can you install a reactor on one of the primary lines in order to drop the voltage across the reactor and thus present a lesser voltage at the primary of the transformer. The more I think about this solution the more I think it wont work, because the voltage drop across the reactor will be dependent on current in the primary which will change depending on the load on the secondary and therefore vary the voltage on the primary?

Change the tap?

 

[a.bisnath]

a matter of cost

a matter of cost

cost will determiine the course of action,there was a situation shere I used a a ballast type resistor/potentiometer with suitable wattage to drop the voltage in a control circuit in a 20 amp load control circuit it does get warm but it has been working for 20 years the book "electric wiring diagrams" by RH ladley may help,

 

[kingpb]

Perhaps you could provide more detail on how a single phase 2:1 ratio (460-230V) transformer is getting 260V on the LV side when 480V is applied to the HV side?

480V is only about 5% above the 460V rating so there shouldn't be an overvoltage rating issue. Hooking up 480V to the +5% tap on HV side would give you about 260V LV side though.

 

[wasasparky]

...talking auto-transformer which is dependent on load.

No, not as simple as that.

If applied at the end of a long feeder and the load cycles on/off, you could have higher than wanted voltages under no-load.

 

[mbeatty]

cost will determiine the course of action,there was a situation shere I used a a ballast type resistor/potentiometer with suitable wattage to drop the voltage in a control circuit in a 20 amp load control circuit it does get warm but it has been working for 20 years the book "electric wiring diagrams" by RH ladley may help,

I have seen resistor load banks used, but they put out a fair amount of heat and are probably not practical.

 

[ohmhead]

Well theres many ways to drop your voltage i see it differently than your point of load changes on secondary .
I also see that it is the wrong transformer as you stated buy a new one . Load is load resistor or no resistor that will not effect transformer everyday transformers see loads swings if that was to happen we would have bigg problems .

You will spend more in watts to lower it down on secondary
but if you want to spend more money buy a variac transformer and adjust to what you need and feed both transformers on that circuit if its just a control circuit and small load put both on it .

Most electronic power supplies have a voltage regulator in circuit 30 volts should not effect them how is it effecting them or is this some other control devices on this circuit thats the issue ?