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scr firing circuit for ac motor speed control


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hi guys
Can anyone who is knowledgeable in power electronics or just any field help me.I want to build and simulate the scr firing circuit for ac motor speed control,for my project.This firing circuit should involve switching to operate a high current device.My circuit is comprise of op-amps,pulse transformer,scrs and other components and I am simulating with Pspice vol 9 or 10 (refer to attached cct).But questions are what are factors need to consider in designing such circuit?Do I have to define my amout of voltage or maximum current?Ok,suppose the supply ac voltage is 240volts and 50Hz,single phase.

Secondly,I've simulated the circuit in blocks,where i generated the square waves(14volt peak-to-peak) in the inverted and noninverted op-amps(uA741)=>
shave or shape it with bjts,capacitors and op-amps into sawtooth=>summed the sawtooth signals in the mixer.But the problem comes in the last bjt(bc 547) to pulse transformer,scrs,ac load or motor and supply in triggering the circuit to generate the pulse(refer to figure of the required pulse,attached).

Can anyone help me in this circuit in configuring,triggering scrs,generating the pulse,related general info on firing circuits,factors to consider in designing this kinda circuit,in fact any information related to this topic is welcome...my email is [email protected] kindly assist me.

Waiting for assistance


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