The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Forum Software Upgrade coming soon...
by Webmaster
Today at 12:03 AM
Re: Fabricating Guards out of Lexan?
by frank
Yesterday at 04:11 PM
Would ELV branch circuits be a good idea?
by gfretwell
Yesterday at 01:26 PM
Why cables look like they do
by Texas_Ranger
Yesterday at 12:33 PM
100% breakers?
by Texas_Ranger
01/16/17 06:13 AM
New in the Gallery:
Desk-mounted "power-board"
Top Posters (30 Days)
Webmaster 20
HotLine1 19
gfretwell 13
Trumpy 12
ghost307 12
Who's Online
1 registered (Webmaster), 0 Guests and 69 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#69138 - 08/29/06 04:01 PM Lathe motor
derater Offline

Registered: 03/30/02
Posts: 182
Hope this is an ok area for the ?. Cust. has a Powermatic 3520b lathe and all I can find is that it's 3 or single phase, 2hp. Someone (co. ?) told him it takes a 40a breaker. Does this seem excessive? Resi basement location.

Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#69139 - 08/29/06 04:38 PM Re: Lathe motor
Bob Offline

Registered: 02/05/02
Posts: 182
Loc: Mobile, AL, USA
Look on the motor nameplate and get the FLA
(full load amps). If its single phase the FLA should be about 12 amps. Use a 25 or 30 amp breaker. If its 3 phase the FLA should
be about 7 amps. 15 or 20 amps breaker. usually a residence does not have 3 phase service. You may have to change the motor.

#69140 - 08/29/06 04:57 PM Re: Lathe motor
electure Offline


Registered: 12/24/00
Posts: 4229
Loc: Fullerton, CA USA
Don't be too quick to jump to the conclusion that it's a 230 volt wired motor.
A 2hp motor will draw about 24 amps when wired for 115.
If that were the case, a 40A Breaker wouldn't be excessive

#69141 - 08/29/06 05:11 PM Re: Lathe motor
LarryC Offline

Registered: 07/05/04
Posts: 782
Loc: Winchester, NH, US
If it a 3 phase motor, you can use a small VFD to generate the 3 phase from a single phase input.


#69142 - 08/29/06 05:47 PM Re: Lathe motor
derater Offline

Registered: 03/30/02
Posts: 182
Thanks guys. It's an either/or unit. I don't carry 8-2 in the van and was hoping against another trip for wire. Electure, is that run or start? Does that apply?

#69143 - 08/30/06 08:09 PM Re: Lathe motor
RobbieD Offline

Registered: 02/23/03
Posts: 238
Loc: Canada
Here is the link with the manual for the lathe. It seems wierd that in the specs it doesn't list the FLC. It does state that it is a 230v motor like you said single/or three phase.

#69144 - 08/30/06 09:13 PM Re: Lathe motor
NORCAL Offline

Registered: 09/25/02
Posts: 807
Go to page 13 of the manual, it already has a inverter.

#69145 - 08/30/06 09:32 PM Re: Lathe motor
Scott35 Offline

Broom Pusher and

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Viewed the .PDF manual, available from the link that RobbieD provided.

Found out the following about this Lathe:

    [*] The Lathe Motor is powered and controlled via an intregal VFD, which is Factory installed,

    [*] The Motor is a TEFC make, rated for 2 HP at 220V, 60 Hz,

    [*] No indication if the 2 HP Motor is Single Phase or Polyphase - but seeing that the Motor is controlled by a VFD, I am thinking it would be a Polyphase Motor - likely a Wye connected TEFC type 3 Phase Squirrel Cage Induction Motor,

    [*] The machine may be connected to either a 1 Phase 230 Volt power system, or a 3 Phase 230 Volt system,

    [*] If 1 Phase 230 Volt, 2 Wire system is used, the Factory's Standard 3 wire cord, supplied with the machine, may be used and no alterations need to be made to the machine,

    [*] If 3 Phase 230 Volt 3 Wire system is used, the cord needs to be changed out with a 12/4 cord, and termination alterations are required.

No FLA ratings are listed anywhere, so it seems like the Branch Circuit might be best rated for the FLA of a 2 HP 230 Volt 1 Phase Squirrel Cage Induction Motor.

As viewed by the NEC, this would result in at least 12 FLA for a 230 Volt Motor, and at least 13.2 FLA for a 208 Volt Motor.

Looks like a 20 Amp Circuit would be sufficient for the Lathe, and a Breaker from 20 Amps to 40 Amps could be used.

Definitely need to do these two things first:

1: Check the nameplate's ratings, and base circuitry ratings from that,
2: RTFM!!!
(stands for: Read The Fu..,, err... Fine Manual)

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#69146 - 09/01/06 04:32 AM Re: Lathe motor
derater Offline

Registered: 03/30/02
Posts: 182
Thanks all- I finally got to see the lathe; nameplate read 17.5a @ 240v 1ph.Used 10-2 for the circuit,20a bkr. Why 'they' told the h/o 40a is beyond me.


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals