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1636[atlas_craftsman] Re: No Subject

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  • J Tiers
    Jan 1, 2000
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      For electric motors reversing means depends on type.
      For normal AC motors of single phase, you usually have two wires that you
      reverse to switch directions. It only works when the motor is stopped or
      slowing down. This can be done with a DPDT switch. Some are not reversible.
      Three-phase motors you reverse any two wires. These will reverse from full
      speed, or "plug".
      For DC motors, Permanent magnet types are directly reversible by swapping
      "Universal" motors like drills, vacuum cleaners etc, and probably your
      treadmill, are series motors, and you must reverse internal wires, either
      the ones going to the coil, or the ones going to the brushes, but not both.
      They also will "plug", but you may get a substantial arc.
      Another note: Most switches or relays must be derated by 10 or even 20 times
      on current or voltage if used on DC. A switch rated for 15 amps 120V AC may
      only take 1/2 amp at 90V DC. At 12V DC, it may be good for 5 or 10 amps.
      This is due to arcing, which is increased by voltage. Arcing welds the
      contacts, and causes failure as material is gradually transferred from one
      to the other. In extreme cases, the switch or relay may not actually open
      electrically, as the arc bridges the gap even when fully open physically.
      The contacts will rapidly melt in such a case.

      -----Original Message-----
      From: SLEYKIN@... <SLEYKIN@...>
      To: atlas_craftsman@egroups.com <atlas_craftsman@egroups.com>
      Date: Saturday, January 01, 2000 6:45 AM
      Subject: [atlas_craftsman] Re: No Subject

      >The motor I am using IS the one from surplus center. To reverse it you
      >to bring the wires from the brushes out to a cross connected DPDT switch as
      >it is not a PM type motor. It works very well however you should plan to
      >the motor in the CW direction for normal use and only occasionally
      >it for the odd things that reverse is handy for. The brushes have an
      >"offset" to them that make them more efficient in the CW direction. I have
      >not been able to notice any difference. These are VERY torquey motors and
      >the feedback speed regulation makes them maintain a pretty constant speed
      >over varying torques. There are a couple of mods you will want to do to
      >the ramp up time shorter and to let you start them at a preset speed rather
      >than having to start from dead slow every time. The mods are in the 1998
      >dropbox archive under treadmot or I can send them of to anyone that needs
      >them/can't find them.
      >Hope this helps / makes sense :)
      >In a message dated 12/31/1999 1:51:28 PM Pacific Standard Time,
      >alstrux@... writes:
      >> Sent message From: alstrux@... (alfred piszcz) Date: Fri, Dec
      >> 31, 1999, 4:06pm To: sleyki-@... Subject: treadmill motor
      >> Hi
      >> Noticed your response in the A-C user group . Is the motor you
      >> are using similar to the one advertised by SURPLUS CENTER in the
      >> Jan/Feb issue of HSM ? This one looks good but doesn't mention anything
      >> about reverse. It only mentions CW rotation. But if it is a true DC
      >> motor it should be easily reversible by using a DPDT switch shouldn't
      >> it,or does that only apply to permanent magnet motors? Any help will
      >> be appreciated.
      >> Thank you.
      >> Al Piszcz
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