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  1. #1
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    Apr 2013
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    Default Single Phase Motor and amps

    I came across this motor on FB market place and unfortunately missed out. I have a couple of questions for future reference:

    1) Is it always the case, the higher the voltage the higher the amps? It seems with newer motors as soon as you jump up to 4HP the amps it draws is over 15amps which requires a larger Earth terminal on the plug.
    2) This is a single phase. It looks like you can wire it to use 480 volts and therefor drops the amps. Can you run this motor off a normal single phase outlet?

    kW: 3.7
    Amps: 22.0/11.0
    RPM: 1445
    Volt: 240/480
    Phase: 1

    Screenshot_20201116-055805_Facebook.jpg Screenshot_20201116-055828_Facebook.jpg

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  3. #2
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    Default

    No not off a normal SF outlet. You would need one supplying 22 amps at 240V.

    The 480v supply would require a special transformer supply and it would be cheaper to get [email protected] (if you have that much available).

  4. #3
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    Perth
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    Default

    These size/types of motors are usually hard wired in and have their own individual line and breaker.

    What are you looking to drive with such a large motor?

  5. #4
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    Default

    Thanks Guys,

    Bob, large bandsaws (32" - 36"). I have a few of these I am restoring. The smallest motor between them is a 3hp 3-phase and the largest being 7hp 3-phase (from memory). I liked the size of this motor but is probably not necessary as I would think a 3HP motor will be sufficient on these big bandsaws. I can get a cheap motor per below which will do the trick. The good thing is these will draw under 15amps so just need a 15amp outlet + plug, so no special considerations as normal households cater for this for the most part.

    2.2kw 3HP 1400rpm shaft 28mm Electric motor single phase 240v

  6. #5
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    Perth
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    Quote Originally Posted by Charlie_6ft View Post
    Thanks Guys,

    Bob, large bandsaws (32" - 36"). I have a few of these I am restoring. The smallest motor between them is a 3hp 3-phase and the largest being 7hp 3-phase (from memory). I liked the size of this motor but is probably not necessary as I would think a 3HP motor will be sufficient on these big bandsaws. I can get a cheap motor per below which will do the trick. The good thing is these will draw under 15amps so just need a 15amp outlet + plug, so no special considerations as normal households cater for this for the most part.c
    Thanks for that. Regarding power requirements, it depends what you plan to cut with them.

    Old large bandsaws were made in the 30+" size range so they could have deep throats so large pieces could pass on the inboard side of the blade. The other interest was depth of cut or ripping depth capability which is limited by the distance between the wheels. Once this goes above a 12" then you may need more than 3HP. FWIW the horizontal milling bandsaw I use has a 36" diameter wheels and a 36" wide cutting capability and that has a 27HP Kohler motor. It uses a 50mm wide 1TPI blade.

    Just a reminder that to be legal 15A sockets should be wired by a dedicated line to their own dedicated breaker.

  7. #6
    Join Date
    Nov 2008
    Location
    Sydney
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    Default

    Quote Originally Posted by BobL View Post
    Thanks for that. Regarding power requirements, it depends what you plan to cut with them.

    Just a reminder that to be legal 15A sockets should be wired by a dedicated line to their own dedicated breaker.
    That reminder is not supported by AS/NZ 3000:2018, nor by the now obsolete AS/NZ 3018. You will note that the requirement under the Standard is 20A, not 15A as is so often stated in this forum.

    The following extract from AS/NZ 3000:2018 is quite specific. The older AS/NZ 3018:2001 also had tables of allowed GPO/CB/cable combinations which included 2x 15A sockets on a 2.5mm 20A circuit. Both HPM and Clipsal have double 15A combination outlets in their product ranges, HPM also sell a 15A/10A combination.

    "C5 NUMBER OF POINTS CONNECTED TO CIRCUITS
    C5.1 Number of circuits
    Each item of equipment that has a current rating in excess of 20 A per phase should be connected to a separate and distinct circuit.
    Where more than one item of equipment is to be connected to a circuit, consideration needs to be given to
    (a) the number, distribution and type of equipment (lighting, socket-outlets or appliances, etc.), i.e. points, that are to be supplied in combination;
    (b) the operating characteristics of the different items of equipment, including seasonal or daily variations;
    (c) the circuit current under expected operating conditions and the coordination with cable and protective device ratings to minimize the risk of an overload fault; and
    (d) the effects of an overload fault on the circuit, including loss of supply to equipment that performs a special function, e.g. security, emergency, medical or critical information and telecommunications purposes."

    Chas.

  8. #7
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    Default

    Thanks for that. I was going off what a sparky that wired our mens shed told me. I guess he was trying to wrangle a few more $$ out of our shed. Id be surprised if any sparky was to put a 15A GPO on a std household 10A cIrcuit. I do know about the double 15A GPOS as I have 5 in my shed.

  9. #8
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    Default

    Good info chaps. So in regards to the below motor drawing a max of ~14amps (at startup) I am guessing whilst in normal use a 10amp GPO will suffice, but it's best practise to have a 15amp GPO installed?

    2.2kw 3HP 1400rpm shaft 28mm Electric motor single phase 240v

    As far as the size of the motor goes the below motors where used on a couple of these saws. I am led to believe in going to a 3hp single phase motor equivalent will result in 35% less torque when compared to a 3-Phase motor.


    Motor HP Phase Volts AMPS RPM Cycles (Hz) RATING
    Crompton 2.75 3 400/440 5 940 50 CONT
    K. L. Electric Co. 3 3 415 4.3 1425 50 CONT

  10. #9
    Join Date
    Nov 2016
    Location
    USA, Indiana, West Lafayette
    Posts
    147

    Default

    Quote Originally Posted by Charlie_6ft View Post
    Good info chaps. So in regards to the below motor drawing a max of ~14amps (at startup) I am guessing whilst in normal use a 10amp GPO will suffice, but it's best practise to have a 15amp GPO installed?

    2.2kw 3HP 1400rpm shaft 28mm Electric motor single phase 240v
    No. 13.9 A is the current drawn by the motor when loaded to it's full rating. The actual current drawn in use depends upon lots of things, including feed rate, blade sharpness, material thickness and toughness, etc. The rated power is a recommended limit, not an ultimate limit. It's like the speed limit on a highway, exceed it at risk. If the operator exceeds the limit the motor will draw more than it's rated current (as well as exceed it rated temperature rise and possibly not meet it's rated lifetime, depending on ambient temperature).

    Startup current, according to the spec you linked, will be about 70 A.
    Single Phase Motor and amps-gmyl-jpg

    Startup current in the table is given by the LRA/RLA parameter. LRA is Locked Rotor Amps and RLA is Rated Load Amps. So, 5 x 14 = 70.

    Quote Originally Posted by Charlie_6ft View Post
    I am led to believe in going to a 3hp single phase motor equivalent will result in 35% less torque when compared to a 3-Phase motor.
    You've been misled. Rated torque depends upon rated power and rated rpm. Pick any two and the third one is determined. 15 N-m and 1400 rpm is 2.2 kW regardless of the number of phases, the voltage, the current, etc.
    Attached Images Attached Images
    Dave

  11. #10
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    Quote Originally Posted by Charlie_6ft View Post
    Good info chaps. So in regards to the below motor drawing a max of ~14amps (at startup) I am guessing whilst in normal use a 10amp GPO will suffice, but it's best practise to have a 15amp GPO installed?
    Yes

    As far as the size of the motor goes the below motors where used on a couple of these saws. I am led to believe in going to a 3hp single phase motor equivalent will result in 35% less torque when compared to a 3-Phase motor.
    Nope - as dmorse says the motors are normally rated on their outputs with rpm/HP/torque being closely related.

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