this is the circuit in question, page 3 is the part I'm asking about, not the PWM circuit on page 1,2: http://kitsrus.com/pdf/k166.pdf The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. The LM324 Quad op-Amp limits Voltage to 32V What is an op-amp that will work here, but be able to handle 100v or maybe 55v min? As far as current and total wattage , I'm looking for min 100A , ideally 500A As far as Wattage/practical heat dissipation, obviously ideal Wattage would be (500A*100V) , I would think many many mosfets working together would be the only practical solution to heat dissipation/wattage. I'm a 1rst year EE major, we haven't covered this stuff at all, I made the original circuit, but want it to handle more power. I've wanted to make this circuit since I was 13 years old, I've been saving this huge brushed DC motor since I was 13 Thank you so much!
how to get this PWM DC motor control to handle more power
Started by ●October 28, 2008
Reply by ●October 28, 20082008-10-28
causalitist wrote:> this is the circuit in question, page 3 is the part I'm asking about, not > the PWM circuit on page 1,2: > http://kitsrus.com/pdf/k166.pdf > > The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. > > The LM324 Quad op-Amp limits Voltage to 32V > > What is an op-amp that will work here, but be able to handle 100v or maybe > 55v min? > > As far as current and total wattage , I'm looking for min 100A , ideally > 500A > As far as Wattage/practical heat dissipation, obviously ideal Wattage > would be (500A*100V) , I would think many many mosfets working together > would be the only practical solution to heat dissipation/wattage. > > I'm a 1rst year EE major, we haven't covered this stuff at all, I made the > original circuit, but want it to handle more power. > I've wanted to make this circuit since I was 13 years old, I've been > saving this huge brushed DC motor since I was 13 > > Thank you so much! >You'll need an industrial-strength power line to fire it up! You definitely need to investigate a career in power electronics if this sort of thing turns you on. The op-amp solution is slow, weird (op-amps don't make good comparators), and subject to shoot-through. The generally recognized way to do this, unless you are intent on saving money on the circuit at the expense of a protracted design cycle, is to use a gate driver on the MOSFET. Something like a HIP4082 will let you use N-channel MOSFETS (or NPN IGBTs) while taking care of at least some of necessary MOSFET drive issues. You won't be dissipating 50kW. If you assume an 80% efficient motor drive then you'd be dissipating "only" 10kW, but you can probably do better than that if you hold the PWM frequency down. You can get some pretty big MOSFETs (and some astonishingly large IGBTs), so the "real" problem is finding a heatsink that will work on your budget. I'd keep doing web searches for circuits, and maybe get a book on power electronics. Good luck. If you work at it long enough it'll be your senior project. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html
Reply by ●October 28, 20082008-10-28
On Tue, 28 Oct 2008 10:58:38 -0500, "causalitist" <nate53143@hotmail.com> wrote:>this is the circuit in question, page 3 is the part I'm asking about, not >the PWM circuit on page 1,2: >http://kitsrus.com/pdf/k166.pdf > >The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. > >The LM324 Quad op-Amp limits Voltage to 32V > >What is an op-amp that will work here, but be able to handle 100v or maybe >55v min? > >As far as current and total wattage , I'm looking for min 100A , ideally >500A >As far as Wattage/practical heat dissipation, obviously ideal Wattage >would be (500A*100V) , I would think many many mosfets working together >would be the only practical solution to heat dissipation/wattage. > >I'm a 1rst year EE major, we haven't covered this stuff at all, I made the >original circuit, but want it to handle more power. >I've wanted to make this circuit since I was 13 years old, I've been >saving this huge brushed DC motor since I was 13 > >Thank you so much! > > >The only practical way to do this would be using a microprocessor to monitor current and voltage levels, generate the pwm outputs, and to set the precise duty cycles required for the load. 500A out of a bank of lithium ion batteries will cause your mosfets to smoke is a millisecond if not controlled very precisely. In addition, you need to worry about the inductive effects of the motor, which will can cause huge spikes which will violate the voltage restrictions on the mosfets when the current is changed. You'll also need big heatsinks. I'd start small, maybe 20A, and see where that takes you. You'll learn as you blow things up. You can get really cheap parts to smoke at the various online surplus electronics outlets, like goldmine-elec.com. Pick up a bunch of P and N hv mosfets, and a bunch of shottky diodes (which you'll use to protect the mosfets). For $50, you can get way more parts than you'll need during the learning process. Once you figure out the gotchas, you can buy real parts at digikey or mouser. How big is the motor? Are you building a car? Regards, Bob Monsen
Reply by ●October 28, 20082008-10-28
Robert Monsen wrote:> On Tue, 28 Oct 2008 10:58:38 -0500, "causalitist" > <nate53143@hotmail.com> wrote: > >> this is the circuit in question, page 3 is the part I'm asking about, not >> the PWM circuit on page 1,2: >> http://kitsrus.com/pdf/k166.pdf >> >> The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. >> >> The LM324 Quad op-Amp limits Voltage to 32V >> >> What is an op-amp that will work here, but be able to handle 100v or maybe >> 55v min? >> >> As far as current and total wattage , I'm looking for min 100A , ideally >> 500A >> As far as Wattage/practical heat dissipation, obviously ideal Wattage >> would be (500A*100V) , I would think many many mosfets working together >> would be the only practical solution to heat dissipation/wattage. >> >> I'm a 1rst year EE major, we haven't covered this stuff at all, I made the >> original circuit, but want it to handle more power. >> I've wanted to make this circuit since I was 13 years old, I've been >> saving this huge brushed DC motor since I was 13 >> >> Thank you so much! >> >> >> > > The only practical way to do this would be using a microprocessor to > monitor current and voltage levels, generate the pwm outputs, and to > set the precise duty cycles required for the load. 500A out of a bank > of lithium ion batteries will cause your mosfets to smoke is a > millisecond if not controlled very precisely. In addition, you need to > worry about the inductive effects of the motor, which will can cause > huge spikes which will violate the voltage restrictions on the mosfets > when the current is changed. You'll also need big heatsinks. > > I'd start small, maybe 20A, and see where that takes you. You'll learn > as you blow things up. > > You can get really cheap parts to smoke at the various online surplus > electronics outlets, like goldmine-elec.com. Pick up a bunch of P and > N hv mosfets, and a bunch of shottky diodes (which you'll use to > protect the mosfets). For $50, you can get way more parts than you'll > need during the learning process. Once you figure out the gotchas, you > can buy real parts at digikey or mouser. > > How big is the motor? Are you building a car? > > Regards, > Bob MonsenEverything Bob says, except the microprocessor is optional. A good analog controller will do just fine. Of course, it may be _easier_ to do with a micro, but it's not _necessary_. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html
Reply by ●October 29, 20082008-10-29
On 2008-10-28, causalitist <nate53143@hotmail.com> wrote:> this is the circuit in question, page 3 is the part I'm asking about, not > the PWM circuit on page 1,2: > http://kitsrus.com/pdf/k166.pdf > > The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. > > The LM324 Quad op-Amp limits Voltage to 32V > > What is an op-amp that will work here, but be able to handle 100v or maybe > 55v min?you may have to build your own. 100v signal transistors are fairly common Bye. Jasen
Reply by ●October 29, 20082008-10-29
On Oct 29, 2:58=A0am, "causalitist" <nate53...@hotmail.com> wrote:> this is the circuit in question, page 3 is the part I'm asking about, not > the PWM circuit on page 1,2:http://kitsrus.com/pdf/k166.pdf > > The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. > > The LM324 Quad op-Amp limits Voltage to 32V > > What is an op-amp that will work here, but be able to handle 100v or mayb=e> 55v min? > > As far as current and total wattage , I'm looking for min 100A , ideally > 500A > As far as Wattage/practical heat dissipation, obviously ideal Wattage > would be (500A*100V) , I would think many many mosfets working together > would be the only practical solution to heat dissipation/wattage. > > I'm a 1rst year EE major, we haven't covered this stuff at all, I made th=e> original circuit, but want it to handle more power. > I've wanted to make this circuit since I was 13 years old, I've been > saving this huge brushed DC motor since I was 13 > > Thank you so much!The circuit that you have is only suitable for flea power compared with what you are talking about. It would be hpelessly inefficient at high power levels As some of the other contributors suggest, browse the applications information of the Power Electronics companies like IR. I'd suggest that you use a High and Low side driver like an IR2110 with a separate 12 or 15V power supply for the control circuit. Use all N-channel MOSFETs - they are cheaper for a given current and voltage. Make sure in an H-bridge with an inductive load like a motor, that the voltage rating of the FETs is at least 2x the supply voltage due to the parasitic transistor dV/dT breakdown phenomenon. Make sure the main power supply has good bypassing - big capacitors with short leads. What you are attempting is difficult and dangerous. You will certainly create some smoke from failed devices. Learn but please do not die trying. Cheers, Hugh. 25 years of Power Electronics!
Reply by ●October 29, 20082008-10-29
"causalitist" <nate53143@hotmail.com> wrote in message news:ls6dnT0v_5Izq5rURVn_vwA@giganews.com...> this is the circuit in question, page 3 is the part I'm asking about, not > the PWM circuit on page 1,2: > http://kitsrus.com/pdf/k166.pdf > > The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. > > The LM324 Quad op-Amp limits Voltage to 32V > > What is an op-amp that will work here, but be able to handle 100v or maybe > 55v min? > > As far as current and total wattage , I'm looking for min 100A , ideally > 500A > As far as Wattage/practical heat dissipation, obviously ideal Wattage > would be (500A*100V) , I would think many many mosfets working together > would be the only practical solution to heat dissipation/wattage. > > I'm a 1rst year EE major, we haven't covered this stuff at all, I made the > original circuit, but want it to handle more power. > I've wanted to make this circuit since I was 13 years old, I've been > saving this huge brushed DC motor since I was 13 > > Thank you so much! > >Check out these forums, there is usually a thread running about how to build high power PWM motor speed controllers. http://www.diyelectriccar.com/forums/ http://www.evforum.net/forums/ http://visforvoltage.org/ Mike>
Reply by ●October 29, 20082008-10-29
"causalitist" <nate53143@hotmail.com> wrote in message news:ls6dnT0v_5Izq5rURVn_vwA@giganews.com...> this is the circuit in question, page 3 is the part I'm asking about, not > the PWM circuit on page 1,2: > http://kitsrus.com/pdf/k166.pdf > > The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. > > The LM324 Quad op-Amp limits Voltage to 32V > > What is an op-amp that will work here, but be able to handle 100v or maybe > 55v min? > > As far as current and total wattage , I'm looking for min 100A , ideally > 500A > As far as Wattage/practical heat dissipation, obviously ideal Wattage > would be (500A*100V) , I would think many many mosfets working together > would be the only practical solution to heat dissipation/wattage. > > I'm a 1rst year EE major, we haven't covered this stuff at all, I made the > original circuit, but want it to handle more power. > I've wanted to make this circuit since I was 13 years old, I've been > saving this huge brushed DC motor since I was 13 > > Thank you so much! >I read the circuit oscillates at 270 hz, I've noted most commercial controllers oscillate at a higher frequency so you don't have to listen to them sing. I've seen 18khz used. I couldn't get the LM324 to work at 18 khz with the circuit I tried. Mike P.S. Here's how I used my huge brushed DC motor! http://s395.photobucket.com/albums/pp37/Qmavam/?action=view¤t=gokartreduced.jpg> >
Reply by ●October 29, 20082008-10-29
MORE INFO: Thanks so much guys. the motor is about 3.3" diameter, 7 inches long. it's rated at 24v, but it was taken out of a handicap mobility chair. Says CIM EM801-003 on it. I know the 24v rating is very very conservative.. i ran 36v through it last night, (3, 12v lead acids) was cranking pretty good, the wire welded to the battery terminal on startup.. but I let it run 1 hour, and it was barely warm.. doesnt seem to draw too much current once spinning. i ended up buying a different kit, http://www.kitsrus.com/pdf/k67v3.pdf along with a few handfuls of IRFB3206 Pd=300w, Rds=4.1 mOhm max, 75v, 120-170nC Qg (will use these after i burn up the cheap ones) and I took your advice and got a bunch of FQP55N06 and IRF530 from that surplus site you gave me. A REASONABLE HEAT MANAGEMENT/WATTAGE GOAL?: So given the schematic AT http://www.kitsrus.com/pdf/k67v3.pdf, apparently the only way i will get near at least 1000watts is to put many mosfets in parallel, and buy a long, high surface area copper heat sink that they all bolt to, and a good fan. I CANT FIND A LONG COPPER HEATSINK TO BOLT THEM TO .. i cant even find any copper heat sinks for t0-220. so with 85% efficiency, 1000w = 150watts i need to dissipate.. if i use 5 of the IRFB3206, with an awesome copper heat sink they all mount to (which hopefully you guys know where to get) .. that should do it right?? QUESTIONS ABOUT MY CIRCUIT, AND PARALLELING MOSFETS: I am not told that the number of mosfets i put in parallel is restricted by the total gate charge of all added together, and if the PWM signal is too low in current, they will switch slower/get hotter. So i need, or eventually will need to increase the current of my PWM signal. i with the kit67, I intend to give the PWM and motor/mosfet circuits different power supplies. why then couldnt i just use this stock kit67, mosfet and all, as my PWM generator.. meaning: give the kits PWM circuit a small power source... then give the one mosfet in the circuit 5v, but a power supply capable of say, an amp?? so i would then have a higher current pwm signal, that i could use to switch alot of high amp mosfets in parallel.... ? would that work? also, when paralleling mosfets, gate resisters are needed (i'm told) to help get them in sync.. how do I choose these?> >"causalitist" <nate53143@hotmail.com> wrote in message >news:ls6dnT0v_5Izq5rURVn_vwA@giganews.com... >> this is the circuit in question, page 3 is the part I'm asking about,not>> the PWM circuit on page 1,2: >> http://kitsrus.com/pdf/k166.pdf >> >> The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. >> >> The LM324 Quad op-Amp limits Voltage to 32V >> >> What is an op-amp that will work here, but be able to handle 100v ormaybe>> 55v min? >> >> As far as current and total wattage , I'm looking for min 100A ,ideally>> 500A >> As far as Wattage/practical heat dissipation, obviously ideal Wattage >> would be (500A*100V) , I would think many many mosfets workingtogether>> would be the only practical solution to heat dissipation/wattage. >> >> I'm a 1rst year EE major, we haven't covered this stuff at all, I madethe>> original circuit, but want it to handle more power. >> I've wanted to make this circuit since I was 13 years old, I've been >> saving this huge brushed DC motor since I was 13 >> >> Thank you so much! >> > I read the circuit oscillates at 270 hz, I've noted most commercial >controllers >oscillate at a higher frequency so you don't have to listen to them sing.>I've seen >18khz used. I couldn't get the LM324 to work at 18 khz with the circuit I>tried. > Mike >P.S. Here's how I used my huge brushed DC motor! >http://s395.photobucket.com/albums/pp37/Qmavam/?action=view¤t=gokartreduced.jpg > >> >> > > >
Reply by ●October 29, 20082008-10-29
> >"causalitist" <nate53143@hotmail.com> wrote in message >news:ls6dnT0v_5Izq5rURVn_vwA@giganews.com... >> this is the circuit in question, page 3 is the part I'm asking about,not>> the PWM circuit on page 1,2: >> http://kitsrus.com/pdf/k166.pdf >> >> The IRF4905 and IRFZ44 limit current to 74A and 49A respectively. >> >> The LM324 Quad op-Amp limits Voltage to 32V >> >> What is an op-amp that will work here, but be able to handle 100v ormaybe>> 55v min? >> >> As far as current and total wattage , I'm looking for min 100A ,ideally>> 500A >> As far as Wattage/practical heat dissipation, obviously ideal Wattage >> would be (500A*100V) , I would think many many mosfets workingtogether>> would be the only practical solution to heat dissipation/wattage. >> >> I'm a 1rst year EE major, we haven't covered this stuff at all, I madethe>> original circuit, but want it to handle more power. >> I've wanted to make this circuit since I was 13 years old, I've been >> saving this huge brushed DC motor since I was 13 >> >> Thank you so much! >> > I read the circuit oscillates at 270 hz, I've noted most commercial >controllers >oscillate at a higher frequency so you don't have to listen to them sing.>I've seen >18khz used. I couldn't get the LM324 to work at 18 khz with the circuit I>tried. > Mike >P.S. Here's how I used my huge brushed DC motor! >http://s395.photobucket.com/albums/pp37/Qmavam/?action=view¤t=gokartreduced.jpg > >> >> > > >oh ya... as for the diode across the motor.. what specs do you guys think i need? whats the model # of a huge one ? also, as the motor draws massive amps upon startup, i need a huge capacitor from its + to ground right? how the heck does this work? its discharged, then you give the motor power, motor draws alot of amps, as the capacitor charges?? it wouldnt serve the purpose.. the capacitor should be charged, waiting.. then somehow be applied to the motor right when the motor is given power...
