Wiring/Electric Question

[sargentcrunch]

I just bought this motor http://www.ptjindustrial.com/Sierra_Electric_Motor_S1_5_36_56C_p/s1.5-36-56c.htm (I know, single phase motors aren't ideal grinders, but I can't afford a VFD right now, so thats a future upgrade)

It says Full Load Amps is 13.92, so will this run off a 15 amp outlet? It seems like it would, but I am no electrician and I don't want to burn the motor up. Also, could I just buy a 12 gauge 15 amp extension cord, cut the ends off, put a new male end on, and wire it to the motor?

I have never done any electrical work, and I don't want to have any doubt with what I am doing, due to the danger.

Thanks
-Bryan

 

[P.Brewster]

First, you bought a motor with a really high RPM. Generally this is advised against for knifemaking purposes.

It says Full Load Amps is 13.92, so will this run off a 15 amp outlet? It seems like it would, but I am no electrician and I don't want to burn the motor up.

You want some headroom. "The first thing to know is that circuits should only be loaded at 80% of the total circuit load. To help you understand the concept, if you have a 15-amp circuit, the safe operating amperage would be no greater than 12 amps." (http://electrical.about.com/od/panelsdistribution/f/calculateload.htm).

This info is reiterated in the following links:
http://electrical.about.com/od/panelsdistribution/a/safecircuitloads.htm
http://michaelbluejay.com/electricity/maxload.html
http://homeguides.sfgate.com/size-heater-circuit-breaker-42602.html

Also, could I just buy a 12 gauge 15 amp extension cord, cut the ends off, put a new male end on, and wire it to the motor?

12g is good for 20 amps. Some codes require 12g for 15 amps as an extra safety measure, but for your purposes, 12g will handle the current. Anyway, yes, this will work but a switch is the proper way to turn on/off the motor.

Note your motor can be wired for 220v, which will work on a 15 amp, 220v circuit. More volts = less amps.

 

[Ken H>]

3450 rpm motor really needs a pulley setup to gear it down for a 2X72 grinder. The motor you linked to can be direct mounted or flat mounted for pulley drive - which do you plan? Makes a difference if it will work very good. If using a pulley drive, you'll find it works pretty good on 120vac with belts in low/medium speed mode.

With a 4" drive pulley your belt SFPM speed will be just a tad over rpm of drive pulley. 3450 RPM is humming for anything other than hogging.

The FLA amps is what the motor would pull under full load - you got to be really hogging to approach that load. The starting amps is the concern and that should be the LRA (Locked Rotor Amps) of your motor.

As Patrick say, much better if you can wire for 220VAC. A 1.5hp motor "will" work on 120vac, but you do need a 20 amp breaker and be sure you've got (edit to correct) 12 AWG wire from breaker to motor. Use a proper switch to turn motor ON/OFF - breakers are not "designed" to be a switch.

Ken H>

 

[Atlas Knife Company]

3450 rpm motor really needs a pulley setup to gear it down for a 2X72 grinder.
With a 4" drive pulley your belt SFPM speed will be just a tad over rpm of drive pulley. 3450 RPM is humming for anything other than hogging.

As Patrick say, much better if you can wire for 220VAC. A 1.5hp motor "will" work on 120vac, but you do need a 20 amp breaker and be sure you've got 20 AWG wire from breaker to motor. Use a proper switch to turn motor ON/OFF - breakers are not "designed" to be a switch.

Ken H>

1. Use a smaller drive pulley if you're using a 3450 RPM motor. Multiple sizes of drive pulley can be used to achieve different speeds.
2. Use 12 AWG from breaker to motor, not 20 AWG.

 

[Ken H>]

Ooops!!! Glad you caught that typo - #20 AWG would be pretty small. I've corrected original post with "edit".

A 2.5" drive pulley would be pretty small and that would still only reduce belt speed to 2250 SFPM. With a 3450 RPM motor you really need a step pulley setup to reduce speed way down. say a 2" X 5" for low speed which would give a tad over 1400 SFPM with a 4" drive pulley. Reducing the drive pulley to 3" would reduce low speed to around 1100 SFPM which would be good. A 3450 RPM motor really needs a VFD for good work, which is the setup I've got.

Do I favor 3450 RPM motor vs a 1725 RPM motor? Not sure at all - I can argue either side, but the 2hp 3450 RPM 3 ph motor was $127 shipped vs $166 shipped for 1725 RPM, and cost was my deciding factor. $40 difference? All depends on how easy the $40 is to come by.

Ken H>

 

[sargentcrunch]

Thanks everyone, I am simply following the GIB build, and Jamie recommends 3450 rpm for the motor, in another thread he said he finds 1725rpm too slow.