This solid-state thyristor (SCR) switch circuit is perhaps the simplest means of reversing a 3 phase motor. “Static” is a catch-all term that essentially means without moving (mechanical) contacts –the traditional means of reversing is via a pair of contactors that swap two of the three AC lines. However, there are disadvantages to contactors as they are expensive, and have a finite life in repetitive reversing applications. Note that this circuit does not provide speed control as the motor runs at its base speed, nor does it provide zero voltage switching.
Static Reversing 3 Phase SSS Schematic
Gate Driver Control Schematic
How it works
The SCRs that are to be conducting are given a repetitive gate pulse train that both turns them on and keeps them conducting. The gate pulses are generated via a 555 oscillator and isolated via a 4secondary pulse transformer. There
