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  • Help me find a DC speed controller...

    Just pulled apart yet another old treadmill, this time with a very nice Baldor 90VDC continuous-duty frame-56 motor.

    The problem is, the speed controller says 90VDC at 5 amp, or 10 amp with the heat sink (which it has.) The motor, however, says 90VDC at 14.6 amp (to produce 1.5HP at 4800 RPM.)

    I'm presuming that this controller would only give me roughly 2/3rds the speed and 2/3rds the HP, right? Making it something like a 1HP, 3200 rpm motor?

    So to get full power out of this badboy, I need a speed controller that can give me 90VDC at 15 amp. I gave eBay a cursory check, and found one 120V (10 amp) and several 12/24V (at various amperages.) A similarly cursory check of Am.Sci&Surp didn't show any speed controllers at all- which probably means I'm looking in the wrong spot.

    Any suggestions for good vendors or suppliers?

    Doc.
    Doc's Machine. (Probably not what you expect.)

  • #2
    Surpluscenter dot com always has some, but a quick check didn't reveal anything with the snort you're looking for. It looks like to get over the 1hp hump they'd need 180 volts.

    http://www.surpluscenter.com/item.as...tname=electric

    Keep lookin'...

    Comment


    • #3
      KB has some drives that would do it, and you can often find them on eBay. Here's the data sheet for one: http://www.kbelectronics.com/data_sheets/kbcc.pdf I could be more specific, but don't know what other requirements you have (reversing, regulation, etc.) If you do look at one of the KB drives let me know - I think I have a friend with one spare, might go cheaper than eBay.

      Comment


      • #4
        Doc, 90VDC @ 15A: you're talking about a 1500 Watt controller -- that's a big controller, with a big heatsink

        Like Russ says, Minarik and KB make controllers up to 16A, but they're several hundred dollars. You might get lucky on Ebay...
        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

        Comment


        • #5
          Originally posted by Doc Nickel
          Just pulled apart yet another old treadmill, this time with a very nice Baldor 90VDC continuous-duty frame-56 motor.

          The problem is, the speed controller says 90VDC at 5 amp, or 10 amp with the heat sink (which it has.) The motor, however, says 90VDC at 14.6 amp (to produce 1.5HP at 4800 RPM.)

          I'm presuming that this controller would only give me roughly 2/3rds the speed and 2/3rds the HP, right? Making it something like a 1HP, 3200 rpm motor?

          So to get full power out of this badboy, I need a speed controller that can give me 90VDC at 15 amp. I gave eBay a cursory check, and found one 120V (10 amp) and several 12/24V (at various amperages.) A similarly cursory check of Am.Sci&Surp didn't show any speed controllers at all- which probably means I'm looking in the wrong spot.
          Doc.
          Not necessarily true.

          The motor will draw whatever it needs to run with the given load. If the load is not as much it will draw less.

          So you should be able to get full speed, which merely depends on the voltage. You HAVE the voltage available, and the motor won't draw the full amperage unless under full load.

          The ultimate power may be less than the motor maximum, if you are limited to 10 vs 15 amps by the controller.

          However, the controller, if it is the typical rectifier and triac type controller*, can have the triac replaced with a slightly higher rated one, which may gain the full capability that the motor allows.

          Many of those controllers also have feedback of motor speed, which sets the speed fairly "solidly". That can make the ultimate current limit a bit more important.

          It may also have an actual current limiting circuit, which presumably is set for the devices used. That may need adjustment if you are using a larger triac.

          * the most common ones I have seen use a particular TDA controller chip, one that was developed for use in washing machines. Those versions are made with a triac as the controlling device,and have a bridge rectifier to obtain the DC for the motor.

          There are a number of websites with information on defeating undesirable features (like soft-start), and also on "hot-rodding" the units for higher power.
          1601

          Keep eye on ball.
          Hashim Khan

          Comment


          • #6
            Here's an auction with the Minarik 90VDC, 15A controller, apparently with the same motor you have Doc

            http://cgi.ebay.com/ws/eBayISAPI.dll...m=280171561021

            Here's a fancy Minarik 21A PWM controller:

            http://cgi.ebay.com/ws/eBayISAPI.dll...m=200171073039
            Last edited by lazlo; 11-13-2007, 12:23 AM.
            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

            Comment


            • #7
              I fiddled with a Minarik controller from Surplus Center, IIRC #23111
              Anyway, it was rated 5A, or 10A with heat sink. Driving a PM
              treadmill motor with nameplate of 2.5hp (!?!) presumably at the
              rated 7100rpm and 18A as listed current, the Minarik bogged down
              once the motor speed got up to 1000-1500 range, IOW well below
              max power and began to cut out for a few seconds, then longer
              before finally shutting down for a time. Suspect over current limiting
              was doing its job.
              It had a pronounced cogging at low speeds also, as would be expected
              with an SCR drive.
              Steve

              Comment


              • #8
                Lazlo- Not the same motor (mine's a Baldor, but the layout with the fan and flywheel are almost identical) but that's exactly the same speed controller I have. The tag on the side- which you can barely read in that pic- says 5A, or 10A with the heat sink (which is the aluminum frame it's on.)

                But that's precisely the same controller, down to the tags and labels.

                JTiers- What I'd like to do with this motor is install it in my old JET mill-drill, in place of the 1-1/2 HP 230VAC motor and worn-out vari-drive (that had seven belts and five bearings between the motor and spindle.)

                It's an R8 machine, and I'd like the HP to be able to turn 1" endmills (through aluminum anyway) without risking blowing something up.

                On that note, I'm also looking for a speed controller that'll give me as much torque as possible even at lower speeds. I plan on having a two or even three-step pulley system so I have a range of speeds, but I still might want to run the motor down to 500rpm, and still have the oomph to push a fair drill bit through steel if need be.

                Doc.
                Doc's Machine. (Probably not what you expect.)

                Comment


                • #9
                  Originally posted by Doc Nickel
                  Lazlo but I still might want to run the motor down to 500rpm, and still have the oomph to push a fair drill bit through steel if need be.

                  Doc.
                  Not gonna happen.........

                  The torque is fairly limited for that motor, since it produces its power at a pretty high rpm. You seem to want to go to 10 percent of RPM, and still produce the same or similar power. Not realistic.

                  The power is related to the RPM and the torque. if the RPM goes down, the torque has to go UP for the same power (force x distance).

                  The torque is proportional to the input current, which has a limit. Above that you saturate the iron, or overheat the motor.

                  You MAY get acceptable performance over a 5 to 1 range of speed (and power). But for drilling steel you want to keep power same at a lower speed, which can only be done with a torque multiplier, namely belts or gears.
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Originally posted by J Tiers
                    The torque is fairly limited for that motor, since it produces its power at a pretty high rpm. You seem to want to go to 10 percent of RPM, and still produce the same or similar power. Not realistic.
                    -Oh, okay. I wasn't sure, and I'm no electrician, but I thought I recalled that there was a way to keep max torque yet still drop the speed through something like pulse width modulation... but I suppose I'm not going to find a controller that can do that on eBay for $20, right?

                    So in other words I'm going to need to keep the speed up at probably the top third, and regulate the gross spindle speeds through belting, right?

                    Which makes me wonder about those so-called 115V/3phase motors out of the other treadmills I got earlier in the summer. They came out of some heavy-duty gym-quality treadmills, and the speed controllers/power supplies are huge and complex things. I wonder how well they'd hold up the torque at low speeds...

                    Doc.
                    Doc's Machine. (Probably not what you expect.)

                    Comment


                    • #11
                      Originally posted by Doc Nickel
                      -Oh, okay. I wasn't sure, and I'm no electrician, but I thought I recalled that there was a way to keep max torque yet still drop the speed through something like pulse width modulation... but I suppose I'm not going to find a controller that can do that on eBay for $20, right?

                      So in other words I'm going to need to keep the speed up at probably the top third, and regulate the gross spindle speeds through belting, right?

                      Doc.
                      You CAN "hold torque", but you can't "hold power", by slowing. And the torque ain't that high due to the high speed.

                      So you'd be drilling slower with motor slowed than if you used belts etc.
                      1601

                      Keep eye on ball.
                      Hashim Khan

                      Comment


                      • #12
                        Another Controller Source

                        Try www.youngssurplus.com
                        good people, always an interesting collection of stuff.
                        Robert
                        grumpy old fart
                        www.wirewerkes.com

                        Comment


                        • #13
                          Doc, I scrounged up the almost identical set-up you got there (the controller is the same) and hung it on a mill-drill and was tickled pink with it, so much so, that when I replaced the M-D with a 6x26 mill I moved it over to it and again really liked it.

                          I dont think it'll quite do what youre describing but I think you'll be surprised at what it WILL do --- and to gain variable speed is enough to make me overlook a lot --- I would usually alternate between 2 pulley settings ... a low and a medium speed (90-95% of the time on medium) and when on the lower setting it was quite potent.

                          That controller certainly isnt one of the better ones, -- use it and keep an eye on ebay till a better one comes along. I did, and while I didnt notice any appreciable difference in 'power' the ability to not have to turn the potentiometer back to zero to restart was a definite plus.

                          Dont know how your set-up is, but on the M-D and 6x26, it was too easy a change-over to the DC set-up to NOT do it and see what would happen --- was a 'bolt-up' except for making a bushing to adapt the mills pully to the DC motors shaft.

                          I have since moved on to a Bridgeport clone with 3ph and a VFD----now THATS a sweet set-up!
                          If everything seems to be going well, you have obviously overlooked something........

                          Comment


                          • #14
                            So with the controller I have, it'll probably be roughly a 1HP motor, right?

                            So what happens if I put a heavier load on it? Say a drill binds, bearing siezes, I climb mill too fast, etc. In other words a stall or near-stall condition.

                            Will I blow out the controller? Assume it's a momentary thing, not that I leave it bound up and struggling for more than a second or two. I know something'll overheat if left that way for an extended period, I guess I'm asking if the first indication of a stall or overload will be the speed controller exploding or something.

                            Doc.
                            Doc's Machine. (Probably not what you expect.)

                            Comment


                            • #15
                              Originally posted by J Tiers

                              There are a number of websites with information on defeating undesirable features (like soft-start), and also on "hot-rodding" the units for higher power.
                              Do you have links to these websites?

                              This would be a good discussion thread to supply this information for reference.

                              TMT

                              Comment

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