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Old 04-26-2011, 10:38 AM   #61 (permalink)
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Originally Posted by dcb View Post
yup, that is peak current to drive a gate. We are talking about some very large IGBT's that need to get their gate capacitance saturated/unsaturated very quickly or risk being fried.
MMMmmmm....I'll take mine medium-well.

Looking forward to the PCBs for this, if they will be produced. Hope we can gets some picts of the working machine for us EV groupies : )

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Old 05-19-2011, 04:43 AM   #62 (permalink)
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Getting my head around IGBTs

At the risk of sounding like a complete dill, my understanding of IGBTs is that 1 IGBT module of a suitable capacity (that is another issue) coupled with 1 IGBT driver board can replace the 10 Mosfets, 10 diodes, 16 power caps, the 3 poly caps & the big chunk of copper that is the heat spreader that is currently my power section.
I guess the IGBT module would need to be bolted to the controller case heat sink.
Is an IGBT power section more efficient, more reliable & generate less heat than a Mosfet power section?
Does each IGBT module need its own driver board or can a driver board run several modules?
I dont have big current requirements. The Cougar 511A capacity is enough but I am looking for maximum reliability.
Am I on the right track here?
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Old 05-19-2011, 12:56 PM   #63 (permalink)
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Originally Posted by ianbartie View Post
At the risk of sounding like a complete dill, my understanding of IGBTs is that 1 IGBT module of a suitable capacity (that is another issue) coupled with 1 IGBT driver board can replace the 10 Mosfets, 10 diodes, 16 power caps, the 3 poly caps & the big chunk of copper that is the heat spreader that is currently my power section.
I guess the IGBT module would need to be bolted to the controller case heat sink.
Is an IGBT power section more efficient, more reliable & generate less heat than a Mosfet power section?
Does each IGBT module need its own driver board or can a driver board run several modules?
I dont have big current requirements. The Cougar 511A capacity is enough but I am looking for maximum reliability.
Am I on the right track here?
You're not a dill! I feel the same way, if it helps. Here's what I can tell you, that is correct as far as I know. If it's not, I hope JackBauer comes in and kicks me or something!

IGBT + Driver Board DOES replace the MOSFETS, diodes, heat spreader, and power board.

It does NOT replace the capacitor bank.

One driver board can run a LOT of IGBTS. However, Paul says that he found a way to replace the driver board and it's expensive VLA500-01 drivers ($50 each!) with a $10 solution. I'd wait to hear more about that from him.
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Old 05-19-2011, 01:00 PM   #64 (permalink)
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Ya! I ordered the parts for it, and the digikey stuff came yesterday, but the rest should be here today or tomorrow. Then I'll test it and make a new driver board.
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Old 05-19-2011, 08:30 PM   #65 (permalink)
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Which IGBT to use

Would 2 of the Mitsubishi CM400DU-12F IGBTs driven by 1 VLA500 driver board be a suitable replacement for the standard 500A Mosfet driven Cougar power board?
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Old 05-20-2011, 04:08 AM   #66 (permalink)
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Curiosity has me on the edge of my seat!

MPaul... What is your new design for the IGBT design? Sounds exciting!
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Old 05-20-2011, 08:00 AM   #67 (permalink)
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Fran explained it to me a bit, and I'm trying to fill in the details. Basically, you use a $3 line filter, which is a 3mH 1:1 transformer with thousands of volts of isolation from primary to secondary..

On the primary side, you send a 15v AC signal (or 12v or 24v or whatever you want). The AC signal is the output of a mosfet driver, at about 50kHz to 100kHz. I'm going to just use a 555 timer to generate the pulses that will be the input to the mosfet driver.

Now, the secondary side will have an AC signal, so then you just rectify it with 4 schottky diodes, and clamp it with a zener diode, and then you use a good bulk capacitor so that you now have nice clean isolated DC power. That DC power can be used to power an optocoupler and then a driver for the IGBT or Mosfet bank. Fran's used it for years, and it is WAY cheaper than a vla501 or whatever. It will be a particularly good cost savings for the AC controller, since you need 4-6 isolated supplies in that case.
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Old 05-20-2011, 09:31 AM   #68 (permalink)
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Originally Posted by MPaulHolmes View Post
1:1 transformer with thousands of volts of isolation from primary to secondary..
Hi Paul,

Question, couldn't a simple DC switcher power supply accomplish basicly the same thing

The simple switcher pulsed DC power is also isolated through a 1:1 transformer primary to secondary too ??

SIMPLE SWITCHER Power Modules, Voltage Regulators, & Controllers | National Semiconductor

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Old 05-20-2011, 09:56 AM   #69 (permalink)
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The purpose of the isolated supply is to power an isolated gate driver, so it has to have tiny capacitance since it's going to also be the supply for high side igbts. The DC-DC that the version 2C controller uses doesn't work as a high side isolated supply. YOu have to use a vla15151 or something similar, which is always out of stock and is around $18 each. I'm not sure if the simple switcher would work as a high side isolated supply, or how much they cost. One of the main goals is to lower the price of the AC controller board by a lot, since the mosfet version had 6 of the vla15151. The other goal is to make a replacement driver board for the IGBTs with parts that aren't out of stock. It's a small parts count, and it's only around $5-$6 for the isolated supply part.
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Old 05-20-2011, 10:43 AM   #70 (permalink)
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Quote:
Originally Posted by MPaulHolmes View Post
The purpose of the isolated supply is to power an isolated gate driver, so it has to have tiny capacitance since it's going to also be the supply for high side igbts.
Paul, what is the power budget that you have for the output side of the isolation supply? I'm guessing since the IGBT's are off board from the driver that you have quite a bit of inductance? Any idea what power you need to overcome it? Also, are you going to to make it a dual output so you get a negative voltage to help turn off the IGBTs?

The output side of those MIC4451 (assuming that is what you are still using) have 12A output stages, I'm assuming to help aggressively drive the IGBT inductance/capacitance.

Its amazing that you are going this way. I was reverse engineering a Mitsubishi Air Cond which has an ACIM compressor. The isolation was done with a transformer with 4 isolated secondary windings (one transformer, 4 outputs). I thought AH HA, but then realized we didn't have AC to drive it. I like Fran's idea of driving it with a oscillator, but its going to be noisy and inefficient. The MAX 250/251 use something like what Fran mentions. The primary side switches at 200khz. The transformer for that one is something like the 470-1005-ND @ Digikey.

Sorry, didn't mean to design over your shoulder, just trying to help fill in some data. The key to designing a good secondary stage is going to be developing a power budget for the opto-isolators and the IGBT driver element, including the cap/inductance budget. I'm here to help.

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