Hi Guys,

I need some help to design the SPDT switching between capacitor and inductor in a solid state way. I am now using a mechanical relay which is not efficient especially when frequency is increased. In fact I want to control the switching frequency from a control circuit (like an arduino or 555 timer...etc) for tuning to resonance but I need to know how to make this SPDT solid state switch with mosfets.

desired voltage and current are 500V 40A

If such SPDT solid state relay exists in the market it would be nice also.

 

Look for IGBTs. They are best suited for high voltage switching. It is also recommended that optocouplers are used for better isolation if you have low voltage parts you need to protect.

 

ok thanks. But how to wire them.

 

Some basics -

https://www.google.com/url?sa=t&rct.../slua618.pdf&usg=AOvVaw2iuo-DEdY01npKFn-UdmVA

At those power levels you need to do a thermal design as well. And a plan on circuit
wiring to manage ground currents.

Regards, Dana.

 

Here is a good video on the subject of IGBTs. It talks about many of the things you need to know, from basic wiring to power consumption. For NPN IGBTs, you connect the grounds together at the collector. Then apply your signal to the gate. It will connect your load to ground when powered. But there are certain requirements to have it act like a closed mechanical relay. The video explains it well.

 

If you directly connect a low-impedance voltage source to a capacitor the current will be limited only by the source impedance, switch resistance, wiring resistance, capacitor resistance and stray inductance. At 500 volts the instantaneous current could be hundreds to thousands of amperes.

Beyond that - if you are playing with voltages and currents of the magnitudes stated and asking how to do the switching, I will not offer any suggestions, as it is clear to me you don't know enough to go anywhere near such a circuit. This is orders of magnitude more dangerous than several things that are banned as topics at AAC.

 

For resonance you should not disconnect capacitor from inductor.
Use this simple circuit:

 

20 kW is a lot, and 1 kV FETs do not have the ultra-low Rdson and fast switching frequencies of their lower-voltage cousins. What is your max switching frequency and (if not a 50% square wave) the minimum on or off pulse widths?

Between the Rdson and the transistor bandwidth limits, the devices will be dissipating some serious heat. At 99% overall efficiency (a very difficult number to achieve) it would be at least 200 W. Also, you probably will need multi-amp gate drivers.

ak

 

need to know how to make this SPDT solid state switch with mosfets.
desired voltage and current are 500V 40A
If such SPDT solid state relay exists in the market it would be nice also.

POWEREX KD221K05 Dual Darlington Transistor Module 50A 1000V
This module contains 2 switches, exactly what you need.
But It is easy to obtain resonance and desired voltage with simple, low power circuit (see simulation below).
Average current from 12V power supply in this circuit is 25mA.