Where to buy very large heat sinks?

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gary350

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I have 2 IGBTs CM600HA-24H, 4 600A diodes A672384 and 30 7400uf 200v electrolytic capacitors to build an induction heater using a 225a 65v Lincoln arc welder as the power supply.

I want 2 heat sinks 14" x 18" with 2" fins for the IBGTs, data sheet says 4100w 1200v 600a.

I need 2 heat sink 8" x 14" maybe larger for the 4 diodes.

How much cooling will the diodes need compared to the IGBTs?

This unit will be used 30 seconds to heat 1 part then turned off. Might need to heat 5 parts in a row. Heat sinks will have safety preset 150 degree F thermostats to shut the unit down. Might need water cooling if I use it more than I am planning.
 
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Please list the parts you are going to use.
Post your schematic.
**broken link removed**
Here is one of many catalogs. I have 100s of pounds of heat sinks. I might have some that will work.
 
Why buy? If the voltage is relatively low (compared to the conductivity of ordinary water), just put them in a bucket of water, with or without a continuous flow.

John
 
If I was you I would get a few good sized aluminum bar stock pieces and cross drill them to work as liquid cooled heatsink.

Way smaller and far cheaper to make yourself.

Otherwise as Nigel pointed out just hit up one of use who works with the large industrial power supply gear. Like him I too have a few hundred pounds of high capacity heatsinks of which many are already milled and drilled to hold multiple IGBT brick modules and or diode packs like you are using.

$25 and cost of shipping will get you a huge inline heatsink from a massive VFD unit I scrapped out a while back that held something like 3 IGBT or massive power transistor bricks.

$100 will get you the same heatsink with the bricks and whatever else still on it.
 
There are some flaws in the circuit.
The maximum average current for the 1N5819 is 1A.
In the circuit the peak current is about 6.8A
The lower IBGT gets never on when the upper is conducting because the diode keeps its gate low.
Have you just tried to combine the old self oscillating circuit with a pwm driven circuit ? There will be problems if the pwm frequency and the resonance frequency are not in sync.
 
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You can use heatsinks used for PC cooling, they are common, cheap and cool well with fan assistance.
Heatsinks in free air can dissipate limited power, about 100W no matter how big.

ronsimpson said:
Distilled water! I have used transformer oil, or mineral oil but probably any oil works
Click to expand...
Remind them that the bucket has to be from metal, thermally insulated bucket will be useless.
 
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Les Jones said:
If you have doubts about using distilled water
Click to expand...
The post above me listed "water" and I was trying to push for "distilled water". The water out of my facet is some what conductive and will corrode metal.
Should I be drinking that?
 
gary350 said:
Click to expand...

gary350,

The schematic you show is a Frankensteinian concoction using part hardware PWM, and part self oscillating PWM. (but doesn't implement either one very well)

That creates two independent circuits that are both separately deciding when to turn the mosfets/igbts on and off. Which is a Very Bad Thing.

You can use one type of control, or the other, but you can't mix the two.
 
mineral oil and vegetable oil intended for transformers has a dielectric constant of ~2 which is far lower than water =80 and thus less leakage capacitance.
 
Tony Stewart said:
mineral oil and vegetable oil intended for transformers has a dielectric constant of ~2 which is far lower than water =80 and thus less leakage capacitance.
Click to expand...

I will use HV oil, I buy it at the local power company maintenance shop. A 2 liter soft drink bottle of HV oil is $2. It will be a while before I work on this project I have to remodel our house hope to be finished by April in time to go camping. We plans to spend, spring, summer, fall, camping in National Parks and State parks.
 
good stuff. It may be also possible to use drugstore mineral oil or sunflower oil which has lower organic (VOC) odor and may be suitable for low voltage thermal conductance.

FYI An extremely purified transformer oil is capable of >50kV/mm which can be reduced to 10kV/mm easily for example to the untrained user. Air is ~ 1kV/mm depending on RH% from flat smooth surfaces. So when they send samples for DGA analyis (dissolved combustible gas analysis) they always use very clean glass containers. Typically oil must pass 35kV/mm. It will have an odor that is hard to get rid of, so seal all containers. Get the oil part number and read the MSDS as well. Invisible dust, moisture particles measured in ppm will reduce the BDV thresholds in oil testers due to tribo-electric effects in the dielectric and DC charge buildup resulting in 25~50% reduced BDV or breakdown V thresholds. I have personally verified this. Invisible Iron core dust in oil is even worse for PD effects.

FWIW.
 
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I get new HV oil from the power company. They pump it out of new barrels. I did my own testing this is what I got, 1/8" spark gap will arc at 1000 volts in air but 15,000. volts arcs at 3/4" in air. 15,000. volts arcs at about 1/64" in HV oil. I built my own rolled polyethylene capacitors rated 40,000. volts .01uf for my 10" Tesla Coil. 3 capacitors in parallel with 14,000. volts at 12KW the TC produces 12 foot arcs, 27 foot circle of arcs and sparks from my 3 foot diameter sphere.
 
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Try to use metric for engineering data. Also report if it is AC or DC

The only different in breakdown for AC and DC is the accumulation of charged particles makes DC worse for most dielectrics, but charged particles also can occur to reduce BDV threshold.

- spark plugs are usually 25mil but you indicated 125 mil or 3.1mm thus 314 V/mm indicates sharp needle or dirty air and high RH would be consistent with your results.

- 15kV in 3/4" or 19mm is 790V/mm is also consistent with sharp points or wire and not flat smooth or large round surfaces.

What voltage arcs at 1/64"? (0.4mm)
Poor BDV is consistent as I said before with contaminated samples (non visible) If you can not get >10kV/mm then very contaminated sample. Industry expects >25kV/mm minimum

- polyethylene is capable of 19 - 160kV/mm depending on quality but drops rapidly with rising T and is poor for thermal conductance.

I have performed hundreds of different tests. and one like this with a needle plug in air and compared with transformer insulating Oil (NYNAS)


< mechanical shock induced arc

Other tests I have performed include up to 200kV AC and DC dielectric tests.
If you need info, I have some experience.
 
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