I'm trying to design a solid-state circuit breaker for a 3-phase AC system with a rating of 690 V, 1000 A.

As the stray inductance contributes to the voltage peaks in the system I'm trying to protect the power electronic devices in several fault conditions. Currently I'm simulating several topologies of the same with Simetrix.

It is, however, difficult to find practical values like stray inductance, resistance etc. in the system, to get more practical results from simulations. I've been simulating with a lumped inductance of about 10 mH until now.

What are the factors that I need to keep in mind while designing the same? Also, where can I find the required values to model the circuit efficiently?

enter image description here

This is the single-phase equivalent. Ignore the values of the devices for now.

  • 6
    \$\begingroup\$ Trying to design protection at 1000A when you don't know the inductance is like trying to design brake pads when you don't know whether they'll be fitted to a bike, a car, or a truck. You need to create a specification for the maximum inductance your breaker is designed to handle before you can progress, or you risk expensive (bill of materials) over-design, or expensive (replacement under warranty) under-design. Of course if that specification matches typical power systems, then so much the better. \$\endgroup\$
    – Neil_UK
    Apr 3, 2017 at 8:40
  • \$\begingroup\$ If you could put up a diagram of your model at the moment it would give us an idea of where you have got to in your thinking and help us to help you. \$\endgroup\$
    – RoyC
    Apr 3, 2017 at 8:41
  • 2
    \$\begingroup\$ Usually we put circuit breakers (fuse, magnetic CB,..) to protect from fire caused by some solid state device failure. Now you want to use a solid state device for protection? IMO that is not gonna happen for long time yet. \$\endgroup\$ Apr 3, 2017 at 8:49
  • \$\begingroup\$ @Neil_UK, Thanks for your answer. That's the problem I'm facing, I need specifications for typical power systems to start off with. I'm not trying to implement anything on hardware right now, it's just a small assignment. I'm not able to find any data for the specifications and I myself do not have sufficient experience to know the same. :/ \$\endgroup\$
    – Pujitha
    Apr 3, 2017 at 9:16
  • \$\begingroup\$ @RoyC, In the circuit I'm just switching of the circuit at a certain time and observing the transients. \$\endgroup\$
    – Pujitha
    Apr 3, 2017 at 9:25

1 Answer 1


Start with a standard voltage level, say 33 kV (3 phase LL). Then model your load to get the 1000 A. Use a standard X/R ratio. For a system with significant motor loads - it may be around 10. In such scenarios, you may be able to neglect the line inductance.


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