In practice, is the ganging of a large number of SCRs in parallel often more expensive than an equivalent hockey puck?

Question

In a separate but related question, I asked how EEs normally wire a large number of SCRs in parallel for high current applications. For this 1 example (sample size = 1), I found a single hockey puck to be more costly than an equivalent array of smaller devices.

That question made me wonder, "Is the work of ganging them in parallel of such difficulty that that justifies the price differential between lots of parallel SCRs and an equivalent hockey puck?"

For the purposes of this question, "equivalent" means equivalent off voltage and equivalent on current. For instance, a 10 x 10 array of 100 V, 100 A SCRs can handle the same current and voltage as a 1 kV, 1 kA hockey puck.

The specific scenario that motivated this question is an application powered by 3 kV DC which will conduct 10 kA into an inductive load. On time is 1 ms followed by > 10 ms off time.

My question is twofold:

1. Is it typical for a single hockey puck to be more expensive than an equivalent array of smaller devices? (I'm asking because, while I might be able to find 10 or 20 examples myself, that is small compared to decades of experience that career power electronics people have.)
2. If so, is the reason most likely due to lower demand, or is the work of ganging small devices in parallel so costly that you normally save money by going with the hockey puck? Is one way normally cheaper than the other, or is it one of those things that swings with market conditions? For example, "This week/month/year, hockey pucks are cheaper?" or vice versa.

Answer 1

Thyristors don't really like to be paralleled because it's like paralleling diodes each with a slightly different voltage drop. You need extra junk to make sure they current share properly or else things go awry. The one with the lowest voltage drop will cause all the current to go through it which will cause it to melt or explode.

Answer 2

For instance, a 10 x 10 array of 100 V, 100 A SCRs can handle the same current and voltage as a 10 kV, 10 kA hockey puck.

Herein lies your problem. A 10×10 array of devices has 10 columns of 10 rows.

The ten columns will create 10 paths for current, giving you at most an increase in current by a factor of 10.

With ten devices per column, they can withstand up to ten times as much voltage.

Your design can handle up to 1 kV, 1 kA. But you need 10 kV 10 kA. You need a 100×100 array.

I suspect the added expense of the extra 9900 SCRs will make the integrated "hockey puck" devices more cost efficient.