Golf cart motor controller  - Page 1
Forum section: electronics / projects

author: House91320
author_rank: Regular Contributor
timestamp: June 05, 2011, 04:43:57 am
content: I am in the proses of designing a board for an autonomous golf cart and was wander how thick traces have to be for a 57-200amp motor and 2oz trace thickness.

author: cyberfish
author_rank: Regular Contributor
timestamp: June 05, 2011, 06:00:10 am
content: This calculator is great -http://www.desmith.net/NMdS/Electronics/TraceWidth.html

author: cyberfish
author_rank: Regular Contributor
timestamp: June 05, 2011, 06:02:36 am
content: I'm guessing 200A is stall current. If you want your PCB to be able to sustain that, you'll need huge traces.Better option may be to make sure the motor doesn't stall (or have the controller do some kind of current regulation - if current draw is too high, start PWMing).

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 05, 2011, 07:08:26 am
content: better leave the trace spec for operation amp, during stall, the trace will blow probably saving the other components. even for few amps, you start to put solder on the trace. pcb trace alone is not design for high power application. from the way i see it and experience looking at various of boards.

author: Zero999
author_rank: Super Contributor
timestamp: June 06, 2011, 06:09:34 pm
content: An autonomous golf cart? Sounds like a recipe for disaster.

author: flolic
author_rank: Frequent Contributor
timestamp: June 06, 2011, 06:19:29 pm
content: Quote from: Hero999 on June 06, 2011, 06:09:34 pmHaha!!!Quote from: House91320 on June 05, 2011, 04:43:57 amBetter use some heavy copper plate like this:Or you can solder additional copper strips onto the PCB:

author: Neilm
author_rank: Super Contributor
timestamp: June 06, 2011, 06:33:44 pm
content: I use thishttp://www.miscel.dk/MiscEl/miscel.html. It not only does PCB traces, but also wire, basic circuits, heatsink requirement calculations and much more.Neil

author: scrat
author_rank: Frequent Contributor
timestamp: June 07, 2011, 10:18:00 am
content: 200 A seems too much for a pcb trace (unless it's a very short one), but I've seen heavy current pcb traces reinforced by putting on them some solder bubbles (in practice, on the layout they make some large pads positioned on a matrix above the large trace). Another solution is using busbars.

author: codeboy2k
author_rank: Super Contributor
timestamp: July 05, 2011, 04:17:11 pm
content: Quote from: flolic on June 06, 2011, 06:19:29 pmWhile I was impressed with your handiwork thereI can foresee a cascading failure should one of those MOSFETs experience an overcurrent situation (or other failure), and the thick tracesDON'Tblow. You'll blow the skinny legs off one MOSFET, and the load moves to the remaining MOSFETs which now have more current to handle, and might cause another skinny leg to blow, and so on..... until all the FETs blow their legs, (or blow up) but your thick traces hold strong.Wouldn't it be better and cheaper (less copper) and safer for your FETs, to limit the current to SAFE operating levels, and also fuse it or breaker it above that point, just in case? I'd rather change a fuse or reset a breaker on the outside of the box, than to dig into the enclosure to replace a FET.I admit I have never had the chance to design anything that operates above 10A, but this is what I would be thinking about to design something that can handle a 200A stall load.

author: Bloch
author_rank: Unknown
timestamp: July 05, 2011, 08:12:32 pm
content: Quote from: House91320 on June 05, 2011, 04:43:57 amIf you dont need any advice on how to build DC motor controllers then just jump over thisHere is a grate page with tips on DC motor controllershttp://www.4qdtec.com/pwm-01.html

author: ivan747
author_rank: Super Contributor
timestamp: July 06, 2011, 05:04:59 am
content: Quote from: codeboy2k on July 05, 2011, 04:17:11 pmHere in the Dominican Republic power inverters are very common due to the poor electrical service. A friend of mine told me he once was called by some guy whose inverter was smoking. Every single MOSFET started exploding inside because of an overload. The only thing they could do was to get the hell outta there. Fortunately MOSFETs are relatively cheap compared to the output transformers. (If the transformer would have got fried I am sure they would have it rewound instead of replaced).