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Originally Posted by Joseph Davis Have you run the part numbers to verify that? They are more likely to be IGBTs. | |
Actually I have not run the part numbers because they're upside down or covered in potting compound so I couldn't see them. I didn't think they are IGBTs based on the datasheet for the suspected controller:
http://www.freescale.com/files/analo...et/MC33395.pdf
If IGBTs are 100% interchangeable in MOSFETs in that application, then yeah they could certainly be them. I don't know
that much about motor control. In any case, it doesn't matter.. all the control circuitry is there.. just write new code for the ST uC and do what you want. Assuming the board hasn't failed*.
The "H"s on the application diagram are the three hall effect sensors around the motor.
Wouldn't the turbine fins being stuck/jammed result in a change in current? The motor control unit has current sensing capability; I thought that would be to determine when the motor stops, so the MCU can map out the endpoints of the actuator when the system is first powered on.
Note: the motor control may be a
custom IC from Freescale. It has the Freescale logo and a Freescale part number on it (google search resulted in some pages with the part listed with no description except "SSOP-32" package), but I can't find any reference to what it actually is based on those part numbers. It's just an 8 digit number. I ended up just looking up Freescale's 32-pin components and saw they had these MOSFET drivers... and sure enough the pinout and package matches the connections on the Holset board exactly. This is the ONLY such motor control chip listed on Digikey made by Freescale. I would like to find a pic of one, perhaps they just don't print "33395" on it and the part number is just some specific production run for this device.
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Mmm, more likely they are there to monitor that the turbine fins don't become stuck/jammed, as the frequency the motor is cycled at dictates speed, which measured vs time results in relative position give or take a little slip. Without ever having seen one of these setups in front of me I have a mental image of a motor that doesn't spin far in one direction or the other, just flux the correct poles in slow motion to get the motor to turn over a third of a rotation and of course in the right direction. I could be wrong about all that, as I'm basing it off of AC inductor motor theory as I'm not a big expert on DC motors, but it's the way I'd design the system if it could be made to work like that.
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The motor spins numerous complete rotations to get the full range out of the actuator arm. There is a big gearset in there to gear it down. I haven't had a chance to get the ratio yet. I thought they would just count the on time as well, but then I noticed that the clip that aligns the circuit board to the motor does in fact have three sensors in it, and I believe they're connected to the microcontroller. The motor control unit doesn't support them.
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Originally Posted by HiProfile I would have trashed all that nonesense and just gone with a simple geared motor, TPS-like possition sensor, and maybe an old-fasioned wastegate too (with a boost solenoid). This would be a lot easier to sense and control, especially where an exhaust brake is concerned. It would also allow some fail-safe function with the WG, so you aren't stranded if the VGT system DOES fail. | |
You should buy an HE341Ve then. It has the 0-5
TPS-like sensor for the position, and the actuator already uses a rod design which should be easier for you to adapt to your own controller.
You will still need a wastegate. The variable vanes act as a wastegate on the diesel turbos. Apparently there is gain in efficiency on the diesels by not completely bypassing the turbine, that's why they didn't go with a wastegate. You can read about Holset's reasoning in one of the papers on the UK site (
www.holset.co.uk).
*What I've heard is the reason the HE351Ve units are so plentiful on ebay is because the actuator control units ARE failing, so dealers are replacing them with a newer style unit. I don't know why they would junk the
whole turbo but I heard there is a new low-force actuator so perhaps there are internal changes that makes them obselete.