how to increase ac voltage without a transformer

Thread Starter


Joined Nov 1, 2011
In my country the supply voltage is 230v 50Hz,but normally it will be less than 200v in my area..
During peakload hours at evening supply voltage may even down to 140v...
My problem is that i want to increase the speed of my ceiling fan (rated at 230v and 75watts) during the low voltage hours...

Step up transformer is much can anyone help me by giving an alternate idea..


Joined Jan 11, 2009
Transformer is the way to go. You can use a 30 volt transformer ( cheaper than a step up trans. ) in series with the mains voltage. Be aware of current ratings. This type of project may be at odds with the site policy of keeping voltages safe.


Joined Mar 24, 2008
AAC will permit line voltages being discussed. This is not a power supply application, the normal culprit.

What the OP probably needs is a auto-transformer, where they can adjust the voltages manually. Problem is, if the voltages very a lot, this can be dangerous. In spite of the name, the component does nothing automatically, and if the power line voltage go to their normal voltage levels you could be dangerously overvoltaging your appliances.


Joined Nov 9, 2007
Don't know how much your budget is but a computer UPS (uninterruptable power supply might help). This would take the mains into a battery and output a reasonable mains for a motor in times of low mains.


Joined Jun 2, 2008
A UPS is an excellent solution but it depends on how long your voltage dips last for?

Another solution, although a little wasteful energy wise, would be to use a ATX power supply with a universal mains input to drive a 12VDC to 230VAC invertor?


Joined Nov 30, 2010
I like post#2. I have an overvoltage problem at my house and a cheap, 75 watt transformer in series with the line (in a buck configuration) is enough to knock down the voltage to 120 watts of HPS lights so they don't burn out the bulbs every 2-3 years.

Thread Starter


Joined Nov 1, 2011
Thank u all for your valuable suggestions...
l like post#2 and i am going to do that.
connecting a 30v 3A tranformer and a fan speed regulator in series with the line supply..
so that i can adjust the voltage to the fan according to the supply voltage fluctuations..

I know that while connecting the transformer in series with line supply both should be in same that the two voltage should be added up...

How is my plan..?
will it solve my problem...?