# variable frequency power supply

#### relicmarks

Joined Oct 13, 2006
355
Whats the theory behind a variable frequency DC and AC power supply

1.) What controls the frequency to make it variable frequency in a AC to DC power supply?

2.) What controls the frequency to make it variable frequency in a AC to DC power supply?

Most in my electronic books the frequency in the power supply is FIXEd set to 50hz or 60hz , but how can i make it variable?

transformer,rectified section,filter section, regulator section

Half wave rectifiers are 50hz?
Full wave rectifiers are 60hz?

#### mik3

Joined Feb 4, 2008
4,846
Your question is not clearly understood at least by me. Write it better please.

#### SgtWookie

Joined Jul 17, 2007
22,201
The power company controls whether their AC power output is 50Hz or 60Hz; in the USA it's 60Hz, Europe is primarily 50Hz.

Linear power supply manufacturers design the transformers so that they can be used across a fairly narrow range of frequencies (say, 47-63Hz), but still be reasonably efficient.

Switching power supplies are different animals, and generally run at much higher frequencies (perhaps 50kHz-3MHz). Some newer designs are using FM to reduce narrowband EMI.

#### relicmarks

Joined Oct 13, 2006
355
Some power supplys DC power supply or AC power supplys have a variable frequency parameter knob

Most variable frequency DC or AC power supplys are to control AC or DC motors

How can you take a regular DC power supply and AC powers supply and add this variable frequency knob?

Power supply block diagram:
transformer,rectified section,filter section, regulator section

What sets the frequency? and how can i make it variable ?

A Half wave rectifier is at what frequency? before the filter caps
A Full wave rectifiers is at what frequency? before the filter caps

60hz 120 volts AC input into a Half-wave rectifier , the frequency would be 30hz? because it rectfied the 60hz into 30hz

A half wave rectifier LOWERS the input frequency right?
A full wave rectifier Increases the input frequency by double

60hz 120 volts AC input into a Half-wave rectifier , the frequency would be 120hz? because it rectified the 60hz into double a octave up

#### relicmarks

Joined Oct 13, 2006
355

#### mik3

Joined Feb 4, 2008
4,846

#### relicmarks

Joined Oct 13, 2006
355
no they aren't switching power supplies

They are variable frequency power supplies very different

#### Audioguru

Joined Dec 20, 2007
11,251

A variable frequency needs to have a variable frequency generator circuit that is called an oscillator. A current amplifier is added so it can drive an AC motor.
You can look on Google for a description of a half-wave rectifier and a full-wave rectifier that is completely different from what you say.

#### relicmarks

Joined Oct 13, 2006
355
the fundamental frequency of the ripple voltage is twice that of the AC supply frequency (100Hz) where for the half-wave rectifier it is exactly equal to the supply frequency (50Hz).

Thus when operated from a 60-hertz line, the frequency of the pulses is 60 hertz. This is called RIPPLE FREQUENCY.

The ripple frequency at the output of the full-wave rectifier is therefore twice the line frequency.

The higher frequency at the output of a full-wave rectifier offers a distinct advantage: Because of the higher ripple frequency, the output is closely approximate to pure dc. The higher frequency also makes filtering much easier than it is for the output of the half-wave rectifier.

::Ripple frequency chart::
Ripple frequency for half-wave rectifier is 50hz to 60hz
Ripple frequency for full-wave rectifier is 100hz to 120hz

#### scubasteve_911

Joined Dec 27, 2007
1,202
Going to have to agree with you on this one.. Honestly too many questions from one person to keep up with.

#### SgtWookie

Joined Jul 17, 2007
22,201
Trying to answer his questions reminds me of Heracles and the Hydra.

Anyone have a torch?

#### scubasteve_911

Joined Dec 27, 2007
1,202
Trying to answer his questions reminds me of Heracles and the Hydra.

Anyone have a torch?
lol, excellent analogy ! Maybe this is the torch of this thread? Or, perhaps he will continue undiminished.

You would think someone that determined to learn would pretty much know anything, unless it is a recent fad?

Steve

#### Audioguru

Joined Dec 20, 2007
11,251
Walters was banned from at least one website for making too many simple and stupid questions. He is (was) on a few forums with exactly the same du[plicated simple basic questions.

Maybe he should do flower decorations instead of electronics.

#### SgtWookie

Joined Jul 17, 2007
22,201
I sure don't mind people asking questions; after all, that's what this site is about.

But this particular poster seems to hammer away relentlessly, often in multiple threads. Then he'll reply to his own thread with some random items he found in searches, then ask more questions.

It's as if the answers given aren't quite registering, and meanwhile the goals keep changing.

I don't wish for him to be banned, but I certainly wish he would take more time to research subjects before simply posting a rapid-fire series of questions - and if he can't find an answer, then try to form the questions more completely.

There are plenty of folks that would like help with various things, and it seems that the helpers a tad busy this time of year. Better that we try to help more folks, than concentrate on one person.

#### relicmarks

Joined Oct 13, 2006
355

but there is a such thing as power supplys with variable frequency as i gave the hyperlinks too

i guess these special power supplys are some type of function generator

or they are using a function generator as a power supply

#### scubasteve_911

Joined Dec 27, 2007
1,202
lol, sorry for the questions, here's one more!

#### John Luciani

Joined Apr 3, 2007
477

but there is a such thing as power supplys with variable frequency as i gave the hyperlinks too

i guess these special power supplys are some type of function generator

or they are using a function generator as a power supply
The variable frequency power sources are AC power supplies. An AC power supply
is essentially an amplifier + function generator.

(* jcl *)