Thyrisor drive for a dc motor

[laplace]

i am doing a project to design a thyristor drive for a dc motor, does anyone have some circuits to help to get some ideas. Thanks

 

[Ubergeek63]

put a triac before a bridge rectifier. It is not good for the motor, but it will work. We do it but it takes a huge expensive filter to make it kind to the motor. Actually we use two SCRs as part of the bridge.

Thyristors need to drop to 0A to turn off so you can not use them to control a DC motor from a DC rail.

Dan

 

[crutschow]

Thyristors need to drop to 0A to turn off so you can not use them to control a DC motor from a DC rail.

It's not well known, but there is a circuit called a Jones Chopper that uses two SCRs in a DC PWM type circuit. It was originally described in the old GE SCR Manual. It requires an autotransformer and capacitor as part of the circuit. The autotransformer charges the capacitor which is discharged by the second SCR to momentarily reverse bias the first SCR and turn it off. The complexity of this design has limited its application, but it is an interesting circuit.

 

[Ubergeek63]

It's not well known, but there is a circuit called a Jones Chopper that uses two SCRs in a DC PWM type circuit. It was originally described in the old GE SCR Manual. It requires an autotransformer and capacitor as part of the circuit. The autotransformer charges the capacitor which is discharged by the second SCR to momentarily reverse bias the first SCR and turn it off. The complexity of this design has limited its application, but it is an interesting circuit.

better off with just a FET or an IGBT

 

[crutschow]

better off with just a FET or an IGBT

No argument with that.

 

[laplace]

thanks. what about for field and armature control and btw do you have workable circuits.

 

[Ubergeek63]

thanks. what about for field and armature control and btw do you have workable circuits.

there is not normally a field winding on a DC motor