MOSFET AND IGBT fail in pwm speed control for 260VDC 2200W universal motor

Discussion in 'The Projects Forum' started by kandilx, Oct 21, 2011.

  1. kandilx

    Thread Starter Member

    Oct 21, 2011
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    hi all i am new here , i was working the past 2 weeks to make PWM for an existing 240VAC 2200W but i will run it on DC 260V instead from 20 12V batteries for and electric car project i am working on i did try this circuit
    DPRG: A Simple PWM Circuit Based on the 555 Timer
    with 555 timer but i changed the MOSFET to W26NM60N 26 amps 600V and IRFP460 20 amps 500V both run a small 12v 1A motor good but when trying the 2200w it fail after about 5 s when i try to increase the speed D and S go short circuit and sometimes g and d and s,
    the next step i did is searching for MOSFET driver i did find several and try this one
    http://www.sampson-jeff.com/tcrobowar/motor1/ver1.htm
    (last circuit in the page)
    and i connect a p mosfet to drive and IGBT GT80J101 80A 1kV which btw cost much
    i did run the small motor but fail at the same way with the other
    failed component didn't even get warm before failing
    only once i try connecting 3 parallel IRFP460 and using first circuit it did run for a while all 3 were hot and in the second try only one get warm and fail
    i did find this article very useful but it didnt solve my problem and i did connect fast diodes throw the motor terminals and throw D and S for safety reasons
    all my trials has been stopped now i didn't know what to do and i have a deadline to finish the project before the end of this month
    so help will be appreciated :)
    thanks
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    first thing: please post your schematic and, more importantly, pictures of your layout and/or pcb, especially the driver and power switch section.

    do you have an oscilloscope?
     
  3. kandilx

    Thread Starter Member

    Oct 21, 2011
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    thanks for ur reply :)
    i dont have oscilloscope :(
    this one is the 555 circuit
    [​IMG]


    this one is the driver circuit

    [​IMG]

    values are


    Reference Value Description
    R1 10K 1/4W
    R2 10K 1/4W
    R3 470 1/2W
    R4 10K 1/4W
    D1 1NT4742A 12V 1W Zener
    D2 ? 16A ?V Fast Recovery
    Q1 MTH40N10 40A 100V MOSFET
    Q2 2N3906 Small signal transistor
    Q3 2N3904 Small signal transistor

    here first the 555timer circuit
    [​IMG]

    then the driver circuit
    [​IMG]
     
  4. kandilx

    Thread Starter Member

    Oct 21, 2011
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    0
    the motor
    [​IMG]

    the IGBT
    [​IMG]

    [​IMG]
     
  5. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    The MOSFET is failing because it is not being properly driven. The gate capacitance is being charged through the 10k resistor as the DIS terminal of the 555 only pulls down.

    This results in a very slow turn-on time for the MOSFET. The 2200W motor is almost a short-circuit when stalled. A high current and high voltage simultaneously in the MOSFET destroys the device.

    A proper gate driver must be used. See:-

    http://forum.allaboutcircuits.com/showthread.php?t=60841
     
  6. #12

    Expert

    Nov 30, 2010
    16,298
    6,810
    You should also have a resistance between Q and the pot so it never gets to zero resistance in either direction.

    edit: Sorry. Wrong thinking.
     
    Last edited: Oct 21, 2011
  7. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    I would also say that trialling this sort of thing on a solder-less breadboard is extremely hazardous. Any momentary loss of contact could result in something blowing up. To make matters worse, the layout in your picture is particularly untidy, with long bare leads which could easily short together.

    Doing this work without access to an oscilloscope also seems very difficult. To me, this is like trying to work on a car engine in a darkroom.

    I admire the spirit of people who try to do difficult things with limited resources, but some things are simply too hard to do without a minimum level of equipment and knowledge.

    There is also the matter of personal safety, as you are dealing with lethal voltages. I would strongly advise you to improve the physical layout of your system before going any further.
     
  8. kandilx

    Thread Starter Member

    Oct 21, 2011
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    my last try as i said before was using a p mosfet as a driver for n igbt for the same reason to decrease the switching time the p mosfet shown in the attachment
    second the motor is start at low speed with no problem then while increasing the speed it fail
     
  9. kandilx

    Thread Starter Member

    Oct 21, 2011
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    Totally agree with you , but i am takin extreme care when working with the HVDC btw all voltage in the bread board are 12v only and the mosfet is fixed @ pcb alone
     
  10. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    I agree with everything above:

    1. Use a dedicated Mosfet/IGBT driver IC with the appropriate gate resistor
    2. Don't use a breadboard , instead use a vector-board
    3. Start with less load, increase slowly the load, for example with resistive load bank (incandescent light bulbs or resistors, but consider that cold lamps have a lower resistance than you would think)
    4. Gate return wires and power wires should not be the same, see attachment , leads to gate driver should be short

    5. Get yourself an oscilloscope :D

    The Mosfets die either because of overcurrent (overheating) or overvoltage (voltage spikes). First you have to find out which one is it to be able to find a remedy.
     
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  11. kandilx

    Thread Starter Member

    Oct 21, 2011
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    i dont understand why should not the resistance go to zero what is the problem in this?!
     
  12. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Using a 555 to drive a mosfet to drive an IGBT to drive a motor is going to give you the same problem as using a 555 to drive a mosfet to drive a motor. You need a MOSFET DRIVER. Think of the mosfet gate like a capacitor. Before the mosfet will switch on, that capacitance has to be charged up. The time it takes to go from open to closed will be dependent on the RC time constant of the gate resistor and the gate capacitance. You want to go from open to closed and vise versa as fast as possible to minimize losses. This means that you want your gate resistor to be as small as possible (10K is WAY too high) and you want as much current as possible to rush into the gate and charge up that capacitance. look at true mosfet driver ICs; they have charge pumps inside that will be able to dump a lot of current into your gate.

    The reason you want to switch as fast as possible as I mentioned is switching losses. With 10KΩ gate resistor, your gate charge current is limited to (3-18V? WTF?*) 3v/10,000Ω = .3mA & 18V/10,000 = 1.8mA. Turn-on time = Qg/I (your IRFZ46N has a gate charge 'Qg' of 72nC), so the fastest your mosfet can turn on is somewhere between 240μS and 40μS. during that average of 140μS, your mosfet will be dissipating tons of heat. if your mosfet takes 140μS to turn on, then any frequency above 7KHz will result in the MOSFET never turning completely on. BEST CASE SCENARIO (18V) your turn on time is 40μS, which corresponds to 25KHz. At 25KHz you would have an exact (ugly) sawtooth wave. Painfully sluggish upward rise from open to closed, and then as soon as it gets fully closed, BAM back to open. During this painfully sluggish upward rise, your MOSFET is generating insane amounts of heat very quickly. your PWM to the motor probably looks more like a super weak sawtooth than a square wave. The general rule of thumb is that the turn-on and turn-off time should not account for more than 10% of your PWM period. 5% for turn on and 5% for turn off. You didn't specify, but if 20KHz is the target (common, above audible range) then you need to shoot for a maximum turn-on time of 250nS. That means you need at least 288mA for the gate. size your gate resistor appropriately. mosfet/IGBT gate drive ICs can put out several amps to get your switching times even lower (read more efficient) FYI. The goal is minimize the the sitching time.

    *why did you specify 3-18V? your MOSFET won't turn on at all without at least 4V. the max is 20V and most manufacturers application notes agree that no appreciable gain is achieved by using gate drive voltages above 10V. Most common applications I have seen use 12V drive.
     
  13. kandilx

    Thread Starter Member

    Oct 21, 2011
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    in the beginning i was using only the 555 then and after some readings i realize what you are saying then i searched for mosfet drivers i did found 3 only one did work[​IMG]

    it gives 28mA
    the other one that didn't work at all is this one
    [​IMG]
    it can give according to my calculation 2A maybe there are a component failure do you think it is a good one?
     
  14. strantor

    AAC Fanatic!

    Oct 3, 2010
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    When I say DRIVER, I am referring to a Driver IC, not a circuit. So far I am only an armchair expert; I have never used a driver IC so I cannot recommend one from personal experience. I have been recommended by a guy with a lot of motor control experience to use the IR2113S. I am looking at that, and also these two for my motor controller: FAN3122 (http://www.fairchildsemi.com/ds/FA/FAN3121C.pdf). It claims 7A peak output from the IC itself. And the IXD 630(http://www.clare.com/home/pdfs.nsf/0/6AC7CC624179BDA185257873005D6BE4/$file/IXD_630.pdf). Which claims 30A output. I need these big drivers because my huge MOSFET has a gate charge of 2750nC. you could get away with something a lot less robust (cheaper). have a look at these:
    http://www.mouser.com/Semiconductor...r-ICs/_/N-6j773?Keyword=mosfet+driver&FS=True

    There are tons to choose from with different options.
     
  15. crutschow

    Expert

    Mar 14, 2008
    13,016
    3,235
    As noted you need a high current push-pull type driver to rapidly charge and discharge the gate capacitance of the power MOSFET and minimize power dissipation in the MOSFET.

    Trying to build such a circuit without an oscilloscope to troubleshoot and test it will likely lead to continuing failures. Please find some way to obtain one. You are flying blind otherwise.
     
    strantor likes this.
  16. strantor

    AAC Fanatic!

    Oct 3, 2010
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    +1
    I see you are making a traction motor out of a recycled angle grinder so I assume your budget is small to nil, but there are cheap (I would say "affordable", but that's relative) o-scopes out there. google 'DSO nano'. I have never used one, but read favorable reviews about them. I picked up a used military surplus tektronix o-scope on ebay for <200$ (with calibration and warranty) and I consider it a great investment. If you choose to buy a more expensive used good brand (tektronix) vise a cheaper new limited functionality (DSO nano) o-scope you can have the confidence that you are using a real precision instrument and you will be able to use it indefinately. You only need to buy it once, and it will last. Buy cheap, and you end up buying multiple times, either due to failure or outgrowing it's capabilities. I learned this with multimeters; I went through about 5 cheap meters before I finally dug deep in my pockets for a used Fluke meter. If I had just bought the fluke first, I could have saved myself about 300$
     
  17. kandilx

    Thread Starter Member

    Oct 21, 2011
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    the problem i face here in egypt is that not all ic's are available at the local market , to get the mosfet itself i first go to the stores and ask what type of mosfet do you have :D then i read the datasheet for every one to select the best for my application
    doing things this way is hard and wastes alot of time
    considering the driver only one store in egypt post his product online and i did found only 2 driver IR2110 "High & Low Side MOSFET Driver"
    and IR2112 "High & Low Side MOSFET Driver"
    i am not sure if one of these will work but i will try to buy ir2110 because it seems to be better tomorrow and see
     
  18. kandilx

    Thread Starter Member

    Oct 21, 2011
    69
    0
    i did consider buying an o-scope but this to me was the last solution but then i will have to buy it from egypt because shipping and so takes 10 to 15 days :S
    and btw i am using the angle grinder motor instead of a DC shunt or series motor because this motor is available and with low prices from 25$ to 200$ istead of 1700$ for a dc motor :) so the the idea of my project is to introduce a new way with less cost and available material and components and easily to manufacture
     
  19. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    The IR2110 is not a bad option. If you want to use it you may have a read through section 6 and 7 of THIS application note, that tells you something about layout and gate drive boost.

    The IR2110 also has a shutdown pin that could be used to stop the gate pulses in case of an overcurrent.... Needs some circuitry to detect the overcurrent of course...
     
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  20. kandilx

    Thread Starter Member

    Oct 21, 2011
    69
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    now i connect the ir2110 and used a 4ohm 2w gate resistance but when working @ frequency 144 hz no problem and when working on 2300hz or 14400 hz the ic get hot
    i use this conf. but @ 9 i connect 12v +
    [​IMG]

    edit: i did use only one mosfet the high one only it run the small motor but the ic is getting hot
     
    Last edited: Oct 23, 2011
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