Login Join Maker Pro

# Confused about SCR ratings in three phase bridges

I

#### Ignoramus11316

Jan 1, 1970
0
I am very confused about ratings of SCRs (silicon controlled
rectifiers) in three phase bridges.

Let's say that I have this rectifier:

http://www.ixys.com/l078.pdf

It says that its rating is 116 A at 85 degrees Celsius.

Does this mean that a three phase rectifier bridge, composed of three
such SCRs, can produce a current of 116*3 = 348 amps?

Even if the RMS current of the sum of the three currents is going to
be a little bit less, due to them being out of phase, am I correct
that such a bridge would still be able to produce 300+ amps?

This is for a welder that I am redoing. As an alternative to these, I
have three bigger SCRs with 180A ratings. So I could use bigger ones.

I would like the rectifier part to be capable of producing 300 amps.

thanks

C

#### [email protected]

Jan 1, 1970
0
Ignoramus11316 said:
I am very confused about ratings of SCRs (silicon controlled
rectifiers) in three phase bridges.

Let's say that I have this rectifier:

http://www.ixys.com/l078.pdf

It says that its rating is 116 A at 85 degrees Celsius.

Does this mean that a three phase rectifier bridge, composed of three
such SCRs, can produce a current of 116*3 = 348 amps?

Even if the RMS current of the sum of the three currents is going to
be a little bit less, due to them being out of phase, am I correct
that such a bridge would still be able to produce 300+ amps?

This is for a welder that I am redoing. As an alternative to these, I
have three bigger SCRs with 180A ratings. So I could use bigger ones.

I would like the rectifier part to be capable of producing 300 amps.

thanks

If you look at fig6 on your data sheet It tells you the current rating
and what heatsinks you need. 300A is around the maximum for these
devices.

I

#### Ignoramus11316

Jan 1, 1970
0
If you look at fig6 on your data sheet It tells you the current rating
and what heatsinks you need. 300A is around the maximum for these
devices.

Thanks, yes, the answer was right there. I think that I will use
bigger SCRs, just in case, and limit current to 200A, for now. I may
revise the current limit later.

i

Replies
5
Views
273
Replies
5
Views
826
Replies
18
Views
2K
Replies
1
Views
637
Replies
5
Views
803