Thyristor Stack design
Thyristor Stack design
(OP)
I am in the process of retrofitting a 600 Amps Four Quadrant Thyristor Stack. During this process I noticed that I have to increase the spacing between the two halves of the heat sink to accommodate the bus bars which pass at the center of the heat sink.
One idea that had come up during discussion was to introduce aluminum filler disk (of diameter equal to or slightly greater than the thryristor itself) between the thryristor and the heat sink on both sides of the thyristor. This whole arrangement will be held together by a set of insulated bolt and nut arrangement. Of course I would have to apply heat sink paste at all the contact points.
Is this arrangement acceptable from the point of view of both thermal & electrical conductivity?
Thanks in advance!
One idea that had come up during discussion was to introduce aluminum filler disk (of diameter equal to or slightly greater than the thryristor itself) between the thryristor and the heat sink on both sides of the thyristor. This whole arrangement will be held together by a set of insulated bolt and nut arrangement. Of course I would have to apply heat sink paste at all the contact points.
Is this arrangement acceptable from the point of view of both thermal & electrical conductivity?
Thanks in advance!





RE: Thyristor Stack design
Keith Cress
kcress - http://www.flaminsystems.com
RE: Thyristor Stack design
Another thing I would worry about is the pretension. Is this stack running close to rated current? If only half, or so, I wouldn't be too worrie. But, if close to 100 %, I would think more than twice.
No other way of doing it? Other heat sinks?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Thyristor Stack design
I sure hope you are not using the white heatsink grease on these connections. It is an insulator and will impede current conduction through the device.
RE: Thyristor Stack design
Can you have a special bus adapter fabricated to transition to the bus you want?
RE: Thyristor Stack design
At 600 A, a few flex leads seem to be the best solution. As suggested by Jeff.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Thyristor Stack design
I guess I have to go for a different design. Will think of flex leads as suggested by Shogsgurra.
RE: Thyristor Stack design
Heck, tape the ends for the joints and then go to a motor shop and get a few layers of varnish put on the bar.
RE: Thyristor Stack design
The thermal resistance between the junction and the heatsink is a major factor in determining the maximum rating that you can get out of the stack assembly.
By adding another thermal junction, you are increasing the temperature rise of the silicon and that could be enough to have a major impact on it's long term reliability.
You need to ensure that the two surfaces of the disk are very parallel and very flat. This requires that they are accurately machined.
You need to ensure that a high quality heatsink paste is sparingly applied to the surfaces and that the clamping pressure is correct.
The thermal impdeance added to the thermal circuit comprises one extra thermal junction plus the conductive path of the disk which will have a higher thermal impedance due to is cross sectional area. A copper disk would be a better option than aluminium, but corrosion between the copper and the heatsink would be a potential issue. You would need to plate the copper to reduce the copper aluminium corrosion.
I would suggest finding an alternative route for the busbars.
Best regards,
Mark Empson
L M Photonics Ltd