how to get this PWM DC motor control to handle more power
in [Basics]
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From: Jasen Betts on 29 Oct 2008 05:08 On 2008-10-28, causalitist <nate53143(a)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
From: Huff on 29 Oct 2008 07:10 On Oct 29, 2:58 am, "causalitist" <nate53...(a)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 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!
From: amdx on 29 Oct 2008 10:42 "causalitist" <nate53143(a)hotmail.com> wrote in message news:ls6dnT0v_5Izq5rURVn_vwA(a)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 >
From: amdx on 29 Oct 2008 11:02 "causalitist" <nate53143(a)hotmail.com> wrote in message news:ls6dnT0v_5Izq5rURVn_vwA(a)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 > >
From: causalitist on 29 Oct 2008 13:53
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(a)hotmail.com> wrote in message >news:ls6dnT0v_5Izq5rURVn_vwA(a)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 > >> >> > > > |