Powermax 1000 dead IGBT Q7 advice + help identifying parts needed
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  1. #1
    Join Date
    Apr 2019
    Location
    Germany
    Posts
    4

    Powermax 1000 dead IGBT Q7 advice + help identifying parts needed

    This is my first post, so hey everyone!

    I got a defective powermax 1000 to repair and need some help identifying one or two odd components that are too far gone to be identified.

    My background: hobbyist welder and EE (still in education, 6th year) from Germany

    Tools&Resources available: Multimeter, LCR-Meter, Soldering Iron, Oscilloscope, Lab Power Supply, ...

    The only description I initially got is "it broke, won't turn on" - so I took her apart and it looks like I got myself a burnt IBGT Q7. - Please see below photos.

    Everything apart from the damage seems to be in good condition, seems like the unit didn't get that much use. Was connected for 3x400V (32A breaker) in Germany.

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    It seems to be very similar to the damage in this thread, the damage is just a little more aggressive on this unit. And this seems to be a "Gen 2" PCB.

    I managed to clean up all the charring and made a list of all evident damage:

    Designator State Type Value/Label Characteristics
    Q7 1/2 defective IGBT 2MBI200S-120 Dual 1200V 200A, 24nF, #2 configured G-E always-on
    Q6 possible damage, needs more testing IGBT 2MBI100PC-140 Dual 1400V 100A, 10nF
    L2 functional, light damage Inductor n/A n/A
    R98 burnt, arc damage Resistor Brown-Black-Gold-Gold 1 Ohm 5%
    R99 burnt, arc damage Resistor Red-Black-Black-Yellow-Brown 2M Ohm 1%
    R100 burnt, arc damage Resistor Red-Black-Black-Yellow-Brown 2M Ohm 1%
    R101 possible damage Resistor Red-Black-Black-Yellow-Brown 2M Ohm 1%
    R66 burnt Resistor Brown-Black-Black-Gold 10 Ohm 5%
    R67 burnt Resistor Brown-Black-Black-Gold 10 Ohm 5%
    R28 burnt Resistor Red-Violet-Black-Gold 27 Ohm 5%
    R20 burnt, arc damage Resistor Violet-Green-Silver-Gold 0.75 Ohm 5%
    R?? burnt, arc damage Resistor Yellow?/Gold?-?-Black-Brown
    OR
    Brown-Black-?-Yellow?/Gold?
    Q2 case exploded, 0.3 Ohm short on pin 2-3, open circuit on 1-2, 1-3 Transistor/BJT? …12 // -140

    My plan is to first tackle all the visible damage and then function-check all the components in the PFC section for invisible damage and replace if necessary.

    This machine has quite some power to it, so I am going to take precautions and double-check things. If something goes electrically wrong at this kind of power, it makes for a very bad day.

    For a start, I have ordered a new PFC IGBT (was around 45€) and may order a new Q6 IGBT next as some have suggested in the old thread. All the other components in the PFC section look to be standard off-the-shelf parts that can easily be sourced if only I could identify them.

    I have also checked the input and output diodes and all other IGBTs and have found no further damage there.

    It would be very nice if someone knew what Q2 (last image) or the anonymous resistor (see red circle in photo) was or could provide a photo of it in non-defective state or give any further advice.

    I will happily post my solution to this damage (if I get her up and running again, that is) in exchange.

  2. #2
    Join Date
    Mar 2011
    Location
    Western Washington
    Posts
    3,166

    Re: Powermax 1000 dead IGBT Q7 advice + help identifying parts needed

    I'm guessing you already found this thread... https://weldingweb.com/showthread.ph...sehold-breaker

  3. #3
    Join Date
    Apr 2019
    Location
    Germany
    Posts
    4

    Re: Powermax 1000 dead IGBT Q7 advice + help identifying parts needed

    Yes I read that one, but thanks anyways. Unfortunately, neither Q2 nor the badly burnt resistor (red circle) can be identified from the photos in that thread. Was hoping someone with experience in these units or the same model of plasma cutter is still around and could have a quick look.

  4. #4
    Join Date
    Mar 2011
    Location
    Western Washington
    Posts
    3,166

    Re: Powermax 1000 dead IGBT Q7 advice + help identifying parts needed

    Yeah, I know I looked though the pics.... you might try PM'ing the op on that one... haven't seen him around but you never know... Quite a few guys have the 1000 so maybe someone will pop in with help.

  5. #5
    Join Date
    Apr 2019
    Location
    Germany
    Posts
    4

    Re: Powermax 1000 dead IGBT Q7 advice + help identifying parts needed

    A quick update: The OP replied but unfortunately has no more info on the unit since he got rid of it back then.

    I also found this: https://www.cnczone.com/forums/hyper...nyone-can.html and sent a PM to the OP there.

    In the meantime, I had a quick look at the circuit and it seems actually two sections have failed:

    Section 1 - Flyback System Power Supply

    The blown Q2 seems to have been the main switcher for the nearby transformer T1 which then generates all the "harmless" logic supply voltage rails for the rest of the board (it's basically more or less a standard SMPS). It operates off the intermediate voltage rail, V_BUS.

    Section 2 - PFC/Intermediate Voltage Rail (V_BUS)

    The IGBT Q7 is used as a switcher and diode combination (thats why E1 and G1 of the dual package have been shorted during manufacturing, doing this gets you a powerful, relatively low loss diode) and together with the massive choke in the back right section of the unit forms a boost converter that is generating another (very high) voltage rail labeled V_BUS. V_BUS is 750VDC +/-15% according to the service manual and is backed by the two beefy capacitors. It is used as the intermediate voltage for the output inverter and other parts of the system, the Flyback System Power Supply, Section 1.

    Initial thoughts

    As to what happened to my unit, I summarize:

    That a powerful arc that has formed between the E1 terminal (which hardwired to the rectified mains negative) and the rectified mains positive present on J9 during operation some time during the failure.

    That a (smaller) arc has also formed between the rectified mains positive (J9) and V_BUS positive terminal, terminal C1, of the IGBT Q7.

    That the Q7 IGBT failed. The E1-C1 IGBT (the one configured as a diode) is definitely damaged, tests with the second IGBT in the package, C2E2 have been inconclusive to this point. The arc may have been the reason or a symptom of Q7 failing, I have not come to a conclusion about this yet.

    That the failure also propagated through R98 into the drive circuitry.

    That the failure also propagated through the gate/emitter connector J8 into the drive circuitry.

    This means that the driver ICs in the section may be damaged as well.


    I have yet to find a plausible explanation for all this to happen. V_BUS would not have far exceeded the allowed limits without the protection tripping and preventing the unit from damage.
    Maybe there was EMI present, maybe a massive voltage excursion / HV transient on the mains made its way through the input filters?
    There could have also been conductive dust present.

  6. #6
    Join Date
    Apr 2019
    Location
    Germany
    Posts
    4

    Re: Powermax 1000 dead IGBT Q7 advice + help identifying parts needed

    Good News!

    Today I started off by desoldering all the dead components from the board and putting them in individual labeled boxes for further reference. Then came the hardest part: identifying the unknown components.

    IGBT Q2

    After putting some more thought into the components, I took some dimensions and finally made a guess as to what Q2 must have been. Measuring its physical size with a caliper, we have a TO3PF case. This case is typical for MOSFETs and also IGBTs. So with the bits of part number that were left ant knowing that it runs off the intermediate voltage of 750V, my guess was it could have been a 1400V 12A MOSFET or IGBT.

    I did a bit of research online and after a couple of tries, a magic part number popped up: 1MB12-140, a 1400V 12A IGBT made by Fuji Electric Co., the same MFG as with the Q7 IGBT!
    All available photos matched, and also the little "B" letter at the bottom left corner and the mold marks align.

    To try and confirm this some more, I then googled "1MB12-140 Hypertherm" and found this thread: https://tractorpoint.com/forum/weldi...erm-600--.html at tractorpoint. Seems that same device is also used in the Powermax 600. Makes perfect sense to me for Hypertherm to reuse their logic power supply in all devices they make... why reinvent the wheel every time. So yeah, dead part #1 identified!

    A quick search at digikey returned no results for the 1MB12-140 and all available listings on eBay or other places show ridiculous prices of 30-40€ for this part (I would say it is worth maybe 5-10€), but I am sure that I will be able to replace it with something much better (in terms of specs and price) if required with not much effort.

    Anonymous burnt resistor = R30

    So after sucking off this one, it revealed the label underneath: R30. I put what was left of it under the microscope and identified: Yellow - UNKOWN (maybe Green or Gray) - UNKNOWN (maybe Gray) - Black - Brown which makes this a 4xx Ohm, 1% resistor. The xx is yet to be figured out.

    After further investigation, I found that R30 is used in the over current protection circuitry of the DC-DC driver IC U5 (marking FA13844). It forms a low pass filter for the current feedback signal derived from the shunt resistor R20 (0.75 Ohm) together with C36 (2.2nF).

    This is very good news! This means that the exact value of R30 does not matter all that much as long as it is in the right ball park (of 4xx Ohm). I had a look at the datasheet for the FA13844 and the reference design mentioned there uses 1k Ohm and a 100pF capacitor which gives about 1.6MHz cut-off frequency. Hypertherm used 2.2nF for C36 and with say 470 Ohm, this would give 154kHz cut-off frequency. According to the datasheet, U5 can operate from 10..500kHz so it all comes down to what frequency U5 is set to operate the boost converter at. I will have a look at the circuit around U5 to determine the design frequency and select R30 accordingly, but in summary 470 Ohm should be just fine.

    Next step is obviously to check for invisible damage in the whole PFC and supply section of which I am sure there will be some and then place some orders for parts. My replacement IGBT for Q7 has already arrived. So far, I would estimate parts will be about 50-60€ if I find no further major damage.

    Some over at the other Powermax 1000 thread at weldingweb have suggested to also replace the inverter IGBT, so I guess this would be something to double-check (or maybe just replace it anyways as a precaution).

    Will keep you posted!

  7. #7
    Join Date
    Feb 2012
    Posts
    3,820

    Re: Powermax 1000 dead IGBT Q7 advice + help identifying parts needed

    The part number for Q2 maybee facing the heat sink. Unscrew it and check.

    The resistors are precision so they use fourth band multiplier.

  8. #8
    Join Date
    Mar 2010
    Location
    Ceres, California
    Posts
    3,391

    Re: Powermax 1000 dead IGBT Q7 advice + help identifying parts needed

    In my experience, When L2 , and R98 blow. There has been a failure in the PFC (boost ) circuit.
    The failure dominoes all across the pcb.
    The repair has always been both IGBT blocks and the power pcb. Replace them.
    In the beginning People tried to just replace the PFC IGBT and the circuit pcb, only to have the main inverter IGBT blow.
    Even if it tested good with an IGBT tester. When I saw this failure, all most all of them had single phase 230 volt plugs on them.
    Your power pcb should have tubular resisters all around the large buss caps.
    Good luck on your repair attempt. Be prepared for it to blow again.

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