Our Haas TM-1 mill uses a couple of stovetop heater elements for the spindle braking resistors. I haven't measured the resistance, but they sit in a metal cage on top of the control cabinet. I've never seen them glow.
-- Ralph ________________________________________ From: Peter C. Wallace [[email protected]] Sent: Tuesday, May 21, 2013 8:17 AM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] Superglue, or Loc-tite for that motors flywheel? On Tue, 21 May 2013, Gene Heskett wrote: > Date: Tue, 21 May 2013 10:50:27 -0400 > From: Gene Heskett <[email protected]> > Reply-To: "Enhanced Machine Controller (EMC)" > <[email protected]> > To: [email protected] > Subject: Re: [Emc-users] Superglue, or Loc-tite for that motors flywheel? > > On Tuesday 21 May 2013 10:26:05 Peter C. Wallace did opine: > >> When using bipolar transistors as high power current sinks, make sure >> you are not violating their secondary breakdown specs (a lot easier to >> kill than you might think) >> >> >> Peter Wallace >> Mesa Electronics > > Despite my confidence that I knew what I was doing, it turns out that the > SOA ratings on the bugs I bought and which arrived while I was trying to > get some sleep on a dairy farm in NYS, turns out to suck dead toads through > soda straws, Peter. > > It appears that the only way I can make a 10 amp sink, would be to make >15 > identical circuits and stack them. I'm not all that fond of semi's in > series. > > Page 5 of this link > > <http://www.st.com/web/en/resource/technical/document/datasheet/CD00000005.pdf> > > defines the bad news. Operation in parallel, so they get the full jolt > from the motor, says I'd have to use an emitter R high enough to keep the > individual bug under .350 ma. So a 10 amp sink would need 30 of them. > Sooo, I am back to wondering how much pure R I can find around the place > that is not already in my EDM lashup. That has a pair of 50 ohm 200 > watters, and those, even in parallel, won't do much more than slow it at > about half the rate it was accelerated at by the controller. 10 ohms would > be a more serious load. Using the 5 ohm I have from full speed, it could > exceed 20 amps at the initial contact close an I can see demagnetizing the > PM fields. > > Do you have any better ideas for a semi choice? These $2.25 each ignition > coil switchers sure aren't it. > > Thanks Peter. > > Cheers, Gene MOSFETS are better but for toughness when you are dissipating KW for seconds, a big wirewound resistor can't be beat. So I would try your ignition transistors in switch mode into a say 16 Ohm resistor. If you want to get fancy and do constant current (so you get a faster more linear speed drop instead of exponential), I would use a PIC or something similar driving a MOSFET in switch mode into a low value brake resistor at say 30 KHz and vary the PWM as the voltage drops. PS: we blew a couple 75A 1200V Darlintons trying to make a constant current dynanometer load, so the lesson about secondary breakdown (or FBSOA) kinda sticks with me :-) > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! > My views > <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> > If you have to ask how much it is, you can't afford it. > A pen in the hand of this president is far more > dangerous than 200 million guns in the hands of > law-abiding citizens. > > ------------------------------------------------------------------------------ > Try New Relic Now & We'll Send You this Cool Shirt > New Relic is the only SaaS-based application performance monitoring service > that delivers powerful full stack analytics. Optimize and monitor your > browser, app, & servers with just a few lines of code. Try New Relic > and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
