Hey everyone!

I have a very simple question, with it being more of a reinforcement to my knowledge (hopefully).
In the below circuit let's assume the following:
-120vAC 60Hz Input
-1,000w purely resistive load
-A 90 degree firing angle
What are the SCR ratings and values of the circuitry?


Now the course I am taking we have very simple formulas and may not be exact; however, this is what I have been lead to believe..
PIV/PRV Value = 120*1.414 = 169.68v
Edc = 120 * 0.45 = 54v
iLoad = 1000 / 54 = 18.52A

However, would it not be Edc = 27v and iLoad = 37.04A? Due to the firing angle of 90 degrees and half of your positve AC waveform is cutoff.
Thanks!

 

What's Edc represent?

Do you want peak current or average current for ILoad?

 

What's Edc represent?

Do you want peak current or average current for ILoad?

DC Voltage component that the load will see.

 

DC Voltage component that the load will see.

So the average or the RMS component?

 

So the average or the RMS component?

I'm unsure what you mean exactly. With using just the DC Voltage component can we not obtain the DC Current?

Like I said, we are doing very basic introduction into electronics and don't go to deep into it. However I'm in a stalemate with my Prof and classmates because I believe the answer is 27vDC and 37.04A DC. With them stating 54vDC and 18.52A DC.

 

This might be useful -

http://bitsavers.trailing-edge.com/components/ge/1972_GE_SCR_Manual_5ed.pdf


Regards, Dana.

 

However, would it not be Edc = 27v

Yes, the average voltage across the load will be equal to 27V.

iLoad = 37.04A?

Are you sure?

 

Yes, the average voltage across the load will be equal to 27V.

Are you sure?

If I did my math correctly yes I believe that is correct. As we see 27V DC across the purely resistive 1,000w load we should then see P=IE transpose to I=P/E, 1000w/27v = 37.04A.

 

 

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Thank you. That's what I thought, now trying to explain that to my professor and my classmates has proven to be very difficult.