Increase the frequency of AC current

Frequency multiplier circuits are conventional technology.

 

still not too much info forthcoming from you

Tell us about the electromagnet ...
its voltage and current rating ?.
Is it a commercial or home made electromagnet ?
what sort of AC power supply are you using?
why do you want to vary the switching speed ?
what do you think it will achieve .... ie ... what are your goals ?

Dave

 

Essentially you need to build a variable frequency signal generator that outputs the appropriate waveform for your application. That can drive an appropriate circuit to deal with the voltages and currents you require.

Depending on the frequency range and precision you desire there are many ways to do this, from microprocessor controlled PWM to digitally controlled numerical methods, to counter based DAC's to analog oscillators or multivibrators.

Look at application circuits for the 555 timer. (google 555 variable multivibratorand look at images)



We need more system requirements in order to pin down what is best for your level of expertise.

 

You need a cyclo converter or an AC source from Ametek or Chroma. Easier to buy it than to build it yourself if you have little experience in power electronics.

 

Start with rectifying the source AC. And use it as the power source.

A. Power a variable-speed motor driving an AC generator
B. Use analog sine oscillator with a variable frequency to drive a power amplifier
C. Use a variable frequency digital sine generator to create a sine wave to drive a power amplifier
D. Use a variable frequency digital generator to drive a set of switching elements to approximate a sine wave

I can go on like this for a long time. As noted above, I need more information to narrow the idea stream down