T-Pain Is On A Boat: Re: [Electric Boats] Motor Controller

Monday, June 2, 2014

Re: [Electric Boats] Motor Controller - transistors and questions....

Arby,

I absolutely agree with you that in the long run, using a commercial off the shelf controller would be faster, more efficient, and cheaper than rolling my own.

This is just for the fun and self education of learning how to do it myself. :)

The wooden boat I built a number of years back was exactly the same story. The ONLY reasons for building a wooden boat are:

1) you're crazy, and

2) you just want to do it.

It's not faster, cheaper, and certainly not any easier than buying one! :)

Thanks for the hint about using a voltage pump to allow n-channel transistors on the top half of the H-bridge. I hadn't heard of that yet, and it makes a lot of sense.

So many things to tinker with, so little time!

If only I didn't have to WORK for a living to support my hobbies (habbits?)!!!!

John

From: "Arby Bernt arbybernt@yahoo.com [electricboats]" <electricboats@yahoogroups.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Monday, June 2, 2014 12:53 AM
Subject: Re: [Electric Boats] Motor Controller - transistors and questions....

Hi John,

You should consider using an off the shelf solution in leu of rolling your own. Kelly makes a decent controller, provides an honorable warranty, and takes the hurt out of controller design. I'd wager you'll spend less on a Kelly than you will buying parts at retail, not to mention the time factor. You'll need a current limit section as well, composed of filters and isolated power supplies.

Should you still be jones'ing for the experience, consider using IR high side drivers and DC-DC converters floating on top of your B+ rail. This allows you run all n-channel devices, just like pro's. P-channel devices are difficult to dope, reducing die yield, and increasing cost.

Have a look at ON Semiconductor's 33035 application notes for yur' basic plain vanilla brushless controller. I've got about 2000 of these mounted on 24v controllers, originally destined for scooter motors. I'll donate them for postage to anyone in the group who wants a couple for experimental uses. I've used a bunch of them to drive Phillips IGBT modules at 300v, for example.

I'll include the schematic, heatsink with crappy IRFZ48 mosfets, and circuit board pdf's as well. Sorry, however, no support.

Should an institution be interested in a bunch, contact me off list and we can talk about a bro deal. Limit is three per person, $5 each for shipping and handling.

Be Well,

Arby

On Jun 1, 2014, at 8:45 PM, "oak oak_box@yahoo.com [electricboats]" <electricboats@yahoogroups.com> wrote:

QUESTION: Can power mosfet's be put in parallel successfully? (it seemed that when I tried this in the past, one of them would heat up much more than the other)

I did a little looking around on Mouser, and found the following transistors:

P-channel:
http://www.mouser.com/ds/2/427/73010-279659.pdf (For me, worked on Chrome, but not Internet Explorer...)
SUP90P06-09L - P ch, 60V, 90A $3.84

N-channel:
IXFK230N20T
http://www.mouser.com/ds/2/205/DS100133A(IXFK-FX230N20T)-15588.pdf
200V, 230A, n ch, $18.83 ea

N-channel:
IRFB4115PbF
http://www.mouser.com/ds/2/200/irfb4115pbf-23418.pdf
150V, 104A, n ch, $3.94 ea

It seems much harder to find P-channel transistors at higher voltage levels than N-channel transistors.

I'm assuming that general practice would be to design for only 50% (or less?) of the rated power of the device, so using the P-ch transistor, it would be better for a 24V circuit, and pushing it to go to a 48V circuit.

Maybe 48V at up to 40A or so (assuming you can dissipate the heat from it!). This would get me up to 1900W, which would pretty closely meet my needs.

Thanks,
John

From: "Mark F mark.internet@yahoo.ca [electricboats]" <electricboats@yahoogroups.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Sunday, June 1, 2014 7:34 PM
Subject: Re: [Electric Boats] Re: strange motor controller idea

I have looked into pwm before, I understand the how to provide pwm with a microcontroller, but don't really feel comfortable with how to configure the FET's and which ones to use for 96 volts.

Would you have any references that would be good for this?

Thanks

From: "wewhite74@gmail.com [electricboats]" <electricboats@yahoogroups.com>
To: electricboats@yahoogroups.com
Sent: Sunday, June 1, 2014 4:33:41 PM
Subject: [Electric Boats] Re: strange motor controller idea

Better to use the pwm from the low voltage controller to drive a higher voltage H Bridge setup of FETs
small pwm generator can be as simple as a 555 chip with some caps and resistors driving 4 fets for the H-Bridge