230v to 110v ac using non polarized capacitor

[chandima283]

I want to get 110v ac from 230v using a capacitor. The load will be about 1000w
Can u please tell me what capacitance values should I use for that?

 

[canadaelk]

I do not know the value of such a beast but I think it would be about the size of a VW Beatle. Depending on what you are trying to do, you may be able to use a circuit similar to a light dimmer. E

 

[JimB]

I want to get 110v ac from 230v using a capacitor. The load will be about 1000w
Can u please tell me what capacitance values should I use for that?

You should use a transformer.

Using a capacitor for an application like this is just a fools errand.

JimB

 

[Diver300]

You should use a transformer.

Using a capacitor for an application like this is just a fools errand.

JimB

I agree with JimB

If you used about 3 of these https://uk.farnell.com/1789707 in parallel, and as long as your load is 1000 W, and is purely resistive, and the mains frequency is 50 Hz, you will get about 110 V out.

There are so many things that are likely to go wrong with that.

If you use one of these:- **broken link removed**

Then the voltage will be close to 110 V, whatever the load is (up to 2 kVA), whatever the power factor, and it's isolated.

 

[colin55]

230v to 110v - you only get 3.5mA per 100n That's 35mA per "u" That's 3.5A per 100u

 

[Diver300]

230v to 110v - you only get 3.5mA per 100n That's 35mA per "u" That's 3.5A per 1,000u

Those numbers aren't quite consistent.

35 mA per μF is 35 A per 1000 μF.

I worked on the basis of a resistive load. A resistive 110 V in series with a capacitive 202 V adds to 230 V, because the phases are at 90° to each other. With 202 V across the capacitor, you get 63 A per 1000 μF

For 9 A you only need 142 μF. 3 x 40 μF will give about 7.6 A. In the highly unlikely event that anyone puts that together, they could always trim it with a few smaller capacitors.

 

[colin55]

you get 63 A per 1000 μF

You don't get 63 A per 1000 μF because the cap is not fully charging and discharging.

 

[Diver300]

If the load is resistive, the voltage across it will be in phase with the current.

A series capacitor has the same current in it, so the same phase.

The voltage across a capacitor is out of phase by 90° to the voltage, so the voltage across the capacitor is 90 ° out of phase to the voltage across a resistive load.

The voltages can be thought of as the adjacent sides of a right-angled triangle, so using the sum of squares:-

V[SUP]2[/SUP] + 110[SUP]2[/SUP] = 230[SUP]2[/SUP]

Solving that for V gives the voltage across the capacitor as 209 V, which gives 63A for 1000μF at 50 Hz

 

[colin55]

You are forgetting that the output will be constantly at 110v via an electrolytic and the capacitor will not fully charge/discharge.
This is the argument I had with a designer who charged $9,000 for a design for a customer of mine, and when the capacitor-fed power supply did not deliver the current, he never asked for his fee.

 

[tcmtech]

You would be far better off using a common 115/230 auto transformer. It would only need to be about half the VA rating of your load to work and will solve all your load problems at the same time.

 

[Diver300]

You are forgetting that the output will be constantly at 110v via an electrolytic and the capacitor will not fully charge/discharge.
This is the argument I had with a designer who charged $9,000 for a design for a customer of mine, and when the capacitor-fed power supply did not deliver the current, he never asked for his fee.

I don't think that I was forgetting that the capacitor won't be charged to 230 V.

If a capacitor is connected directly to the mains, the voltage across it is 230 V so the current is 72 A per 1000 μF

If there is a 110 V resistive load, the voltage across the capacitor is 209 V so the current is 63 A per 1000 μF

If there is a 110 V capacitive load, the voltage across the other capacitor is 120 V so the current is 37 A per 1000 μF.

Of course, this sensitivity to the power factor of the load is one reason that I agree with JimB and tcmtech that a transformer would be so much better.

 

[chandima283]

oh
Im willing to power up an 110v air conditioner.
so, can I use a triac for that?

 

[Reloadron]

As mentioned early on in this thread the best, safest and all around way to do this is using a transformer designed for the load. That would include the air conditioner compressor motor. I lived in Europe for years using 220 mains through a transformer powering all my US appliances including a large refrigerator and freezer.

Ron

 

[Diver300]

While it might be possible to use a triac, it would be very difficult to get working correctly, and you would probably get additional heating in the 110 V motor, which would reduce the efficiency of your air conditioner.

You need a transformer. You could use an auto-transformer, which is smaller for the same rating but does not isolate, so any part of your circuit could be at 230 V.

You might be able to modify a microwave oven transformer, but that is quite complicated, and you would need to know what transformers do.

 

[alec_t]

If the 1kW load is a motor or other inductive load you could have major problems trying to drive it via a capacitor used as a 'voltage dropper'. Because of resonances, instantaneous voltage across the motor/load can actually be increased and be much higher than 350V, with risk of insulation breakdown.

 

[chandima283]

I was using an auto transformer. But it gets heated after about 1 hour operation and gives a burning smell. So before re winding it to bear a greater load I searched for something cheaper than the coil ( capacitor or triac ). But now I think re winding it, is better.
Thanks for the replies.

 

[tcmtech]

I was using an auto transformer. But it gets heated after about 1 hour operation and gives a burning smell. So before re winding it to bear a greater load I searched for something cheaper than the coil ( capacitor or triac ). But now I think re winding it, is better.

Rewinding wont do any good if its just too small to do the job which if it overheats after an hour means it probably is.