Driving a high voltage DC motor - Page 1
Forum section: electronics / projects

author: miceuz
author_rank: Frequent Contributor
timestamp: October 18, 2014, 11:59:29 am
content: We have this 120W DC motor on our lathe, It's an old Soviet motor rated for 200V at roughly 2 Amps. I want to make a controller to vary a speed of it.I have no experience in working with this amount of power, so I'd like to ask for some help.I'm going to use 4 300V-600V 5A rated N channel mosfets in H bridge configuration and something like IR2183(4)http://www.irf.com/product-info/datasheets/data/ir2183.pdfto drive them, then just a small micro to PWM IR2183. Am I doing it right?What I should watch out for? How do I choose flyback diodes? How do I estimate current rating for them? Should they be as fast as possible? Should I put small caps accross mosfets too? Any snubber networks?Can anyone recommend another H-bridge driver? Maybe even an integrated solution for what I want to do exists? Say, I imagine there could exist a chip that PWMs mosfets in H-bridge, while varying duty cycle according to an applied external voltage.

author: mjkuwp
author_rank: Unknown
timestamp: October 18, 2014, 12:26:28 pm
content: Do you need to go two directions? or just vary the speed?

author: miceuz
author_rank: Frequent Contributor
timestamp: October 18, 2014, 12:31:10 pm
content: Quote from: mjkuwp on October 18, 2014, 12:26:28 pmYes, I need to go in both directions. It's a motor on horizontal axis of lathe. It has used an ancient magnetic amplifier for speed controll, but that has failed and we have no intention to debug it

author: max_torque
author_rank: Super Contributor
timestamp: October 18, 2014, 12:53:30 pm
content: Considering how cheaply you can buy low power DC motor controllers for these days, i seriously wouldn't bother building my own..........

author: Seekonk
author_rank: Super Contributor
timestamp: October 18, 2014, 02:32:12 pm
content: 2A isn't a lot of current. Doubt that you could get into too much trouble. Definitely use a fast diode. Ever notice that a Schottky 5A diode is the same case as a regular 3A diode. You can likely get away with 5A diodes. If axial leaded, I have used thin tinned sheet metal from electronic shielding in VCR etc. Solder close to the body, it doesn't take much for a heat sink even though the metal is so thin it can be cut with a sissors. Could be fun, but some of those controller modules are so cheap.

author: miceuz
author_rank: Frequent Contributor
timestamp: October 19, 2014, 01:33:02 am
content: Can anyone point me to those avalable and cheap DC brushed drivers? I can't really find them on ebay for what I need - 200V, 2A.All in all I'm totally going to build this myself because science and experience

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 19, 2014, 01:37:50 am
content: An easy way is to use two SCRs with independent triggers, so that you can choose between giving positive and negative pulses from the mains. Might be too much torque ripple for your application.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 19, 2014, 01:55:27 am
content: Quote from: miceuz on October 19, 2014, 01:33:02 amSure, you might need to change your search terms, look for "dc drives"https://www.minarikdrives.com/descriptions/document/250-0387.pdfStuff like that is 100% industry-standard stuff used all over the place.http://www.ebay.com/itm/MINARIK-MM23001C-DC-MOTOR-SPEED-CONTROL-1-PHASE-115-230-VAC-/371166650142?pt=LH_DefaultDomain_0&hash=item566b419f1eCheck your power ratings though, your motor seems awfully small.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 19, 2014, 02:33:37 am
content: Geez this is the company I was looking for. I worked with these a few years ago.http://www.kbelectronics.com/Variable_Speed_DC_Drives.htmlYou toss em into an enclosure, put a knob and two "acorns" (what do you call those things cables go through and you tighten them?) and there you go. Oh and a reverse switch and maybe an e-stop. Those always look cool.From what I recall the drives look like they were designed in the 1970s and somebody bought a million of them and they're still selling those today.