Driving high inductive load with AC

[devonNash]

I am trying to drive a high inductive coil with at least ±3A at a frequency of around 100Hz.The purpose of this is to produce a large magnetic field.The reactance of the inductor is around 60ohms at the frequency of 100Hz.

The driving signal is sinusoidal and bipolar.

Any suggestion on the driving circuit for this would be greatly appreciated.

 

[Sceadwian]

Plug it into the wall? If the reactance is truly 60ohms at 100hz and the current is 3 amps, you would need to feed it 180volts sine wave. At 50/60hz mains you'd need to use perhaps a 2/1 transformer to up the voltage, that's upwards of 500 watts though, lot of big components.

 

[Diver300]

You could put a large capacitor in series. I think that you need about 2600 µF.

Then the coil and capacitor will be tuned to 100 Hz and you only need a fraction of the power. It wouldn't matter if you drove it with a square wave as the current will always be nearly a sine wave.

https://www.cde.com/catalogs/PSU.pdf

These motor capacitors go up to about 400 µF so you would need 6 of those or so. That would be big and expensive. However, the drive circuit would be far less powerful and easier to make.

 

[devonNash]

Hello Diver300, Thanks for your elegant solution.It's a nice idea to get the LC resonance match the driving frequency , so that the reactance of the inductor is negligible.So now the load only has copper resistance of around 8ohms so I can easily use +-30V power supply for the job.

One more thing.I want to test this system later on with wide range of frequencies, which means I need to find a voltage controlled variable capacitor which can work in the range of micro-farads.The varacator diodes which I found only works in the pico-farad range.Any suggestions.Thanks

 

[tcmtech]

Those motor start capacitors wont last very long though being they are designed for intermediate duty use. You would need motor run type instead which usually come in sized of 150 uf or less each.

Here is a link that may prove useful. LC Tank Calculator