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Jet 1221 SP Motor Gets Hot

Discussion in 'Getting Started' started by Glen Schultz, May 16, 2019.

  1. Glen Schultz

    Glen Schultz

    Joined:
    Apr 22, 2019
    Messages:
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    Location (City & State):
    Pawcatuck, CT.
    I have a brand new Jet 1221 Step Pulley lathe.
    Runs great.
    One thing is that after 20-30 minutes the motor gets real hot. After 40 minutes it is too hot too keep my hand on it.
    There is no air path through the motor as it would just fill up with chips but there is a fan on it.
    is this normal ??
    Thanks in advance for your replies.
     
    Paul Lajoie likes this.
  2. Bill Boehme

    Bill Boehme Administrator Staff Member

    Joined:
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    Location (City & State):
    Dalworthington Gardens, TX
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    It's called a TEFC (totally enclosed fan cooled) motor. The motor on my older Jet 1014 mini runs hot. Once I turned a fairly large hollowform using dry wood and the motor was blistering hot ... hot enough to make the label shrivel up and turn black.If I am just turning a pen the motor is warm, but not hot.

    What were you turning?
     
  3. Joshua Rhodes

    Joshua Rhodes

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    May 13, 2019
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    Location (City & State):
    North Augusta, South Carolina
    So this question is for education purposes, the heat that you gentlemen are describing is just part of the process and to be expected or is it a nod to something being wrong with the motor/ potential motor damage?
     
  4. Bill Boehme

    Bill Boehme Administrator Staff Member

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    In general woodturning lathe motors don't get hot, but my observation is that the small motors used on mini lathes are the exception. I had an exciting experience with a Grizzly mini lathe a few weeks ago. While the motor was only borderline hot some other parts were flaming hot.

    This description applies only to small fixed speed AC induction motors (~½ HP)
    (for DC motors with a variable speed drive see the second paragraph)
    A lot of the problem apparently is due to the motor's low efficiency ... the percentage of electrical power converted to mechanical power and the total amount of electrical power used by the motor. The motor in my lathe appears to be able to take the heat, but I wouldn't want to make a regular practice of letting the motor get blistering hot. If you can keep your hand on the motor for several seconds I think it's not too hot. If it's too hot then let the lathe rest until the motor cools down. If it gets hot without turning anything then there is a problem somewhere.

    This description applies to small DC motors (~½ HP) used with a variable speed drive
    (for single phase fixed speed AC induction motors used with step cone pulleys see the first paragraph)
    Internal cooling is a major concern when a DC motor is used with a variable voltage controller because at low speed operation the motor's internal fan can't provide enough air to keep the windings cool. This is especially a concern when taking heavy cuts which means that motor current will be high. Periodically running the motor unloaded at high speed can help with cooling. Another option is to stop turning for a while to let the motor cool down. Some DC motors are designed to dissipate the heat at low speed by using a heat sink.
     
    Joshua Rhodes likes this.
  5. Forrest Forschmiedt

    Forrest Forschmiedt

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    After a few long sessions with my 1221 SP I also was a bit concerned about this. The motor is quite hot to the touch and smells quite hot after 20 or 30 minutes continuous run time. so I asked Jet tech support.

    The fellow's answers were short and sweet. The max operating temp for the 1221 SP's motor is 266f.
    That's not going to be hot to the touch. That's going to be too hot to touch.
    For quick reference though most of us know this, water boils at 212f and most wood will combust well over 500f so it's not likely to combust chips, though I do frequently clear the chip pile.

    And because I'm the kind of guy (Ok, geek!) that needs data points for reference, I found this:
    From https://www.machinedesign.com/technologies/hot-topic-motor-temperature

    What temperature should an electric motor run at?
    The surface temperature of a continuously (and correctly) operating general purpose industrial electric motor will easily be 80 C (176 F) and perhaps as high as 100 C (212 F). You can't keep your hand on a surface that hot long enough to discern differences, and if you try, you could get a nasty burn.
     
  6. robo hippy

    robo hippy

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    One friend had a small Jet lathe that was getting hot like that. One of the capacitors gave out shortly after this started happening....

    robo hippy
     
  7. Forrest Forschmiedt

    Forrest Forschmiedt

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    Are you trying to make me paranoid about my new toy?

    Fortunately, the 1221SP has not much in the way of electronics, being a single-speed AC motor.
    Since it's a new machine with very low hours, that hot motor smell fade a bit with use. If new smells arise I will certainly pay attention and get paranoid all over again! Meanwhile the fire extinguisher is always close at hand in the shop.
     

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