110v supply

[alkv23]

Hi there i have problem with my transformer power supply. The input is 415v and the output is 130v. Now i need 110v from the 130v, so how to get 110v from 130v? Only need to reduce 20v to get 110v. What electric part or electronic part to reduce this voltage???? Plz help to solve my problem. Thanks.

 

[MP1]

Not sure how much current you need from this, but you could use a capacitive divider in the same way you would use a resistive divider in a DC circuit. Two capacitors will divide the voltage and allow you to tap off at a lower voltage as needed. The formula is Vout = Vin*C1/(C1+C2) where C is in Farads.
The voltage output is not dependent upon frequency, however, if the reactance of the capacitors is not large at the frequency of interest (i.e. capacitance value not large enough), the output current capability will be very low.

MP

 

[Kevin Weddle]

I think using one transformer is ideal. Wanting 110vac when your stuck with 130vac might not be worth it.

 

[Gazza1]

Hi there i have problem with my transformer power supply. The input is 415v and the output is 130v. Now i need 110v from the 130v, so how to get 110v from 130v? Only need to reduce 20v to get 110v. What electric part or electronic part to reduce this voltage???? Plz help to solve my problem. Thanks.

How many KVA is your existing transformer?

 

[ante1]

Hi there i have problem with my transformer power supply. The input is 415v and the output is 130v. Now i need 110v from the 130v, so how to get 110v from 130v? Only need to reduce 20v to get 110v. What electric part or electronic part to reduce this voltage???? Plz help to solve my problem. Thanks.

The sensible thing to do (if possible) is to remove a number of turns on the 130V winding to get an 110V output.

 

[AN920]

sometimes it may be easier to wind some more turns in the opposite direction to subtract from the voltage.

 

[ante1]

Of curse, that would also work. These alternatives do not alter the VA rating as other solutions would, at least not noticeable.

 

[Kevin Weddle]

I attempted to wrap bundled magnet wire around a transformer core one time. In theory, the inductance of paralled magnet wire would be low, and it was. So I had a low inductance, low resistance, high current wire. To develop high current, the inductive reactance should not be high anyway, am I right. Sadly, I just couldn't get the impedance high enough to not blow the 20A circuit breaker with no load attached.

 

[audioguru2]

Kevin,
Take a length of wire and connect it directly to 110VAC. It will burn out or will blow the breaker.

Then take the same length of the same wire and wrap it around a transformer's core, making the primary winding of a transformer. What happens when you connect it directly to 110VAC?
Its high inductive reactance reduces its current to nearly nothing if it has enough turns and if the transformer's core doesn't saturate.

 

[Kevin Weddle]

I think a 20A circuit breaker is capable of more current. At the peak of 120vac, the reactance of the transformer is really low, only limited by resistance. I have always thought a fuse was rated for max. current, I know semiconductors like diodes have a surge current rating. I also know of slow blow fuses. I really think wires should be rated for maximum current, as they can only be destructed by a theshold current level, unlike diodes. I don't think a 20A circuit breaker is only capable of 20A, then it blows.

 

[audioguru2]

What are you talking about, Kevin?
The transformer without a load is an inductor with an inductive reactance determined by the inductance and the frequency, not the peak voltage. The reactance is a very high resistance so the current is very small.

A transformer is not supposed to saturate. It is supposed to remain inductive even at the peak voltage of the mains and at the peak current of the load. If it saturates then the inductor is just a piece of very low resistance wire without inductive reactance.

A 20A breaker is supposed to stay conducting with a 20A RMS current. If the current is higher then it blows, but the amount of over-current determines how soon it blows. If the current is 21A then it might take a few hours for it to blow. If the current is 100A then it will blow quickly.

 

[Gazza1]

You guys are thinking too hard. There are two solutions:


1.) If the transformer has "taps" on the winding, you can connect the output to the 85% tap.

110v / 130v = 84%

2.) Get a different transformer.

 

[Kevin Weddle]

Audioguru, you know the rate of change of voltage goes to zero at the peak of the input, it must in order to change direction. A 20A rms current rating sounds right, and I don't know the construction of a circuit breaker. But I thought that a regular piece of wire will break at a threshold current, beneath which is would last a long time. There is a recommended Amperehour rating for wire, but I believe it is because of insulation deterioration.

 

[audioguru2]

A fuse or a circuit breaker is supposed to pass its rated RMS current (the same heating power as DC). It will blow with a delay time according to the amount of overload. With a small amount of overload then the time will be long before it blows. With a high amount of overload then the time will be short.
Most fuses and circuit breakers can pass overload current from a motor starting or a large capacitor charging without blowing.

 

[Kevin Weddle]

Most fuses and circuit breakers can pass overload current from a motor starting or a large capacitor charging without blowing.

Okay, but a copper wire does have a threshold current, doesn't it? If the wire doesn't blow with the current it has through it, it will never blow.

You can't walk away from a wiring job, only to have the wire blow in a few hours.

 

[audioguru2]

In large buildings under construction the electrical inspector turn on everything then takes infrared photos of the breaker panel. Hot spots are shown that later might cause a fire.

An electrical wire has a small amount of resistance. Current in a resistance raises its temperature. Wire doesn't have "a threshold" value of current, it just gets hot and will melt of burn out if its temperature is too high due to too much average current.