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Strange motor - what kind is it? — Parallax Forums

Strange motor - what kind is it?

PhilldapillPhilldapill Posts: 1,283
edited 2009-05-09 01:58 in General Discussion
I've got a couple of large motors of some kind. There are 3 wires. Energizing any pair of wires seems to lock the motor in place. When I connect a pair of wires to the scope and turn the shaft, a clean sine wave is produced with the frequency and amplitude proprtional to the speed. So far, I cannot make the motor turn on it's own by just connecting power to any leads. This makes me think it's a stepper of some kind. However, when I apply power to a pair of leads, the motor locks. Then, applying power to the next pair, it steps to the next position. Basically, when I apply a rotating polarity to the leads, it rotates. Reversing the order makes it go in the opposite direction. Here is a stepping sequence...

Phase:··· ·A··· B··· C
Polarity:·· NC· -···· +

A· B· C
+ NC· -

A· B· C
-· +· NC

A·· B· C
NC -·· +

and so on...


So, any thoughts as to what type this is?

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-05-08 18:15
    It's either a brushless DC motor or a motor designed for 3-phase AC. What kind of voltages does it use?

    -Phil
  • PhilldapillPhilldapill Posts: 1,283
    edited 2009-05-08 18:17
    Not sure what kind of voltage. I measured the resistance of a pair of leads and it's abou 1 ohm. I'm putting 12V on it, and it seems to work fine with minmal heat.
  • LeonLeon Posts: 7,620
    edited 2009-05-08 18:19
    If it's got three wires it's probably a brushless DC motor.

    Leon

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  • kwinnkwinn Posts: 8,697
    edited 2009-05-08 18:49
    Sounds like a permanent magnet synchronous motor. Applying a 3 phase AC voltage produces a rotating magnetic field and the rotor magnets lock to that field.
  • PhilldapillPhilldapill Posts: 1,283
    edited 2009-05-08 18:55
    Hmmm, sounds like that's what it is, kwinn. The motor is rather large. Probably weighs about 10-15lbs, and has a good bit of torque. Grabbing the 3/4" shaft with a pair of vice grips, and trying to turn... is really tough.

    I know those aren't the most exact specifications, but how much do you think one of these could sell for? I believe there was something on the motor that says "6N-m" which I would assume means 6 Newton-Meters(torque). That's about 846 Oz-Inches.
  • kwinnkwinn Posts: 8,697
    edited 2009-05-09 01:58
    No idea what a new one would cost but they tend to be expensive. If you want an idea of price look for similar sized units on the internet.
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