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Oversized Motor Starter Selection?

Discussion in 'ELECTRICAL ISSUES - POWER YOUR MACHINES & SHOP' started by Uglydog, Jul 16, 2017.

  1. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    Question: Can I safely use a NEMA 1 Motor Starter on a 3hp 3phase 9.2amp motor. --Oversized--

    Information: As I move through the rebuild of this 20" Clausing DP rebuild I thought I'd take a break and plow through my surplus motor starters to learn if I had anything which might fit already on hand.
    Turns out I've got multiple NEMA00 and NEMA1. I don't have any NEMA0 remaining.
    Note: I understand that I'd need to find heaters appropriate to the motor.
    On the other hand what are the odds I'm going to over work a 3hp motor 3phase motor running at 1740rpm? The largest drill I'm likely to chuck is a 1inch on account of the minimum spindle speed minimum at 300rpm.

    Thoughts?

    Thank you.
    Daryl
    MN
     
  2. hermetic

    hermetic United Kingdom Active User Active Member

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    As long as you can get the correct heaters for the overloads, no problem, the contacts are usually the same over a fairly wide current range, and can easily cope with the 3hp load.
     
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  3. Ulma Doctor

    Ulma Doctor Infinitely Curious Active Member

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    the Nema 1 is sufficient for 7.5hp @ 200v,
    you are more than fine Daryl :encourage:

    you'll want heaters from anywhere between 9.6 and 10 amps.
    10 amps if you are going to be working it harder, or the voltage is closer to 200v.
    if your volts are higher, 230v, then some where around 9.6A would be ok
     
    Last edited: Jul 16, 2017
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  4. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    Ulma thanks for the feed back and the bushing material (I hope to finish the bushing in the morning).
    My voltmeter coming off the RPC shows a pretty consistent 240v.

    This will be a 2head gang press on a Clausing table.
    Sitting next to this 20inch Clausing is already mounted a WT20" with a cute little two speed motor (1750/850).
    I've been running her without protection. Shame on me.... No sarcasm intended.
    I'm kind of thinking I might fix all that with this build.
    Specifically, a single NEMA1 starter with separate heater protection for the 3hp Clausing, and separate heaters for each of the 2speeds on the WT.
    Heaters would be positioned after the 2speed reversible switch and before the master on/off.

    Daryl
    MN
     
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  5. Ulma Doctor

    Ulma Doctor Infinitely Curious Active Member

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    you are very welcome, i hope you have fun making the bushings!

    at 240v 9.6 amp heaters would be just fine, 10 amp heaters would be just fine too- you don't have to get hung up on decimal places


    as a point of information,
    the heaters should be used in conjunction with a magnetic contactor.
    most times the heaters are contained in a unit called an overload relay

    you can purchase overload relays that have built in heaters and are adjustable over a specified range of operation
    this option is probably less expensive than buying old style heaters.
    for your operation, i'd get an adjustable 9-12a overload and retrofit it to the Nema 1 contactor
    you'd slightly modify the control circuit if there we no overload protection in place (a very simple but critical step), by utilizing a set of normally closed contacts built into the overload relay.

    another point of information, the heaters are not used for regulating main power- just motor overloads.

    if you need help in selection of a suitable motor overload relay and how to install and use the device, i'm more than happy to assist you.
    i may even have a spare overload unit for ya! ;)
     
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  6. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    I don't know what a "motor overload relay" is.
    Please help me identify if any of these might be helpful.
    I'm concerned that these might be the old school two leg motor protection and would like to make sure that I cover all three.
    I'm also casually wading through the pile looking for a drum switch for the very rare occasion that I might want to reverse.
    Please note that thanks to all of you I am learning some stuff!!
    Thanks to all for your ongoing patience.

    Daryl
    MN
     

    Attached Files:

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  7. f350ca

    f350ca Canada Active User Active Member

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    If you can't easily or inexpensively find heaters, you could fuse the input to the starter with 10 amp fuses and bypass the existing heaters. The heaters allow for momentary surges at startup but on a drill press you'd never be starting with a load.

    Greg
     
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  8. Ulma Doctor

    Ulma Doctor Infinitely Curious Active Member

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    Hi Daryl,
    this is an overload relay, it takes the place of the old style heaters
    ol relay.jpg
     
  9. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    Ulma,
    Got it! That's what's in my Colchester. I didn't know what they were called. Merely that they were new fangled heaters.
    I had to swap all of them out when she arrived as I moved her from 440v to 220v. I glad they were included free with the purchase.

    I'm gonna focus on the bushing (mechanical) then come back to the electrical. It may be a few weeks. Please expect this thread to resurface.

    Thank you,
    Daryl
    MN
     
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