Parallel mg1 and mg2

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Dennad
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Parallel mg1 and mg2

Post by Dennad »

Hi all. Help me with the question. If you run mg1 and mg2 in parallel on the inverter and connect it to one electric motor, will it work? Or is it possible to connect only 2 electric motors separately? Inverter Toyota Aqua nhp10
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Re: Parallel mg1 and mg2

Post by MattsAwesomeStuff »

The two motors inside the transaxle are locked at different rotation rates, so, no, bad idea.
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Re: Parallel mg1 and mg2

Post by johu »

I think he wanted to know if you can parallel the two inverters and run ONE motor with them.
It's been done but it is not quite determined if it actually provides more power.
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Romale
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Re: Parallel mg1 and mg2

Post by Romale »

I also have a similar desire. make the output of the GS450H inverter parallel and connect to one motor. it seems to me that this is guaranteed to increase the battery and motor current without overloading the power part.
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Re: Parallel mg1 and mg2

Post by johnspark »

If you parallel the MG1 and MG2 inverter outputs, the number of IGBTs nearly doubles, but there is still the same voltage drop which IGBTs operate with no matter how many IGBTs are in parallel. What will change is the lower effective dynamic resistance of the parallel arrangement of the IGBTs. So the question becomes: does the IGBT voltage drop effect swamp the dynamic resistance of all these extra IGBTs in parallel. From what Johu has heard perhaps not?

PS: I think IGBT voltage drop is about 2 volts depending which IGBT is being considered (I think this is virtually independent of current flowing through the IGBT).
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Re: Parallel mg1 and mg2

Post by Pete9008 »

Agree that paralleling makes little difference to voltage drop and so resistance. What it should do is delay the onset of desat and also helps share the power dissipation over a greater number of modules so reducing IGBT temperatures. The main unresolved question is how well they share especially during switching. I hope to do a few tests on this once I have a working setup.

Edit - there is a bit more detail here viewtopic.php?p=46116#p46116
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Re: Parallel mg1 and mg2

Post by johnspark »

Thank you Pete9008, and I agree with you as especially the 'bit more detail bit'. I guess if you make the wires for the MG1 and MG2 inverter inputs as equal as possible, and also the two sets of wires from MG1 and MG2 inverter to the motor as equal as possible you are helping yourself as much as possible for unequal time in cable rise times.
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Re: Parallel mg1 and mg2

Post by Pete9008 »

Wire lenght probably has less effect than you might expect. On the input side a good rule of thumb is 5ns/m so even an extra meter of cable is pretty small compared to the switching time (few 100ns?). (Edit - best to keep cables short as possible though as long cables and logic level electronic signals don't mix well!)

On the output side you have the same time of flight delays but cable resistance and inductance also impact the sharing. The resistance of 1m of 35mm2 is only around 0.5mR so pretty small compared to the motor and IGBT values (say 100mR?). Afraid I cont be bothered working out the effect of cable inductance at the moment, but I imagine it would be similar ;) . So not negligible but the dominant factor will be the IGBTs and their drive circuits. On the Prius Gen3 the drive circuits and IGBT look identical so I'm optimistic that they will share reasonably well (hope so because it's what I'm planning on using!).
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Re: Parallel mg1 and mg2

Post by Romale »

Pete9008 wrote: Fri Jan 13, 2023 9:57 am I hope to do a few tests on this once I have a working setup.

I don't know how it is with the parallel of the prius inverter, but in the near future I'm going to make tripled power from Nissan power modules note e power. I'm not going to parallel the same phases, but the modules as a whole. so that one 3-phase module turns into just two triple transistors acting as one phase. I think it will be a wonderful experience and nominally expect to get at least 350 kW from such a Frankenstein
IMG-20230111-WA0025.jpg
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