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
Parking lot pole light swap....
by gfretwell
10/24/16 08:46 PM
International Wire Colour Codes
by Tjia1981
10/23/16 12:08 PM
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 14
HotLine1 7
ghost307 7
renosteinke 6
Potseal 4
Who's Online
1 registered (Tjia1981), 292 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#130710 - 10/21/06 08:57 AM 1500HP D.C. motor amps
Jaz Offline
Junior Member

Registered: 10/20/06
Posts: 1
Loc: Mobile Al USA
Hi all,

Can some one point me in the direction for motoer and cable amps?

I have a Q.
A 1500HP D.C. motor compound wound, reversible,
Shunt rated at 100Amps.

How do I work out total amp requirements, I believe this motor runs at 750 Volts.

#130711 - 10/25/06 09:54 AM Re: 1500HP D.C. motor amps
Trumpy Offline


Registered: 07/05/02
Posts: 8532
Loc: SI,New Zealand
Exactly, what do you want to run on the end of this 1500HP motor?.
Next question would be, do you have a DC supply large enough to supply it?.

[This message has been edited by Trumpy (edited 10-25-2006).]
Let's face it, these days if you're not young, you're old - Red Green grin

#130712 - 10/25/06 01:22 PM Re: 1500HP D.C. motor amps
JBD Offline

Registered: 07/12/01
Posts: 599
Loc: WI, USA
An average DC motor draws an armature current of approx 1.5A per HP at 550V.

The armature current varies inversely to the applied voltage so in your case:

1500HP * 1.5A/HP * 550V/750V = 1,650A.

#130713 - 10/26/06 05:30 AM Re: 1500HP D.C. motor amps
resqcapt19 Offline

Registered: 11/10/00
Posts: 2209
Loc: IL
Note that you can't use standard building wire for this application because the armature voltage is above 600 volts. I have used DLO/RHH for this application a number of times. The last 1500 hp DC motor that I worked on needed cables rated for 2156 amps (motor FLA at 1725 times 1.25 for wire size). We used the ampacity for 500 kmil derated to 344 amps because of 4 current carrying conductors in each raceway. The calculation only required 7 sets or conductors, but because of the rules in 310.4 we had to use 8 sets. We had four 4" conduits, each with four 535.3 kcmil DLO cables.

#130714 - 01/05/07 08:34 PM Re: 1500HP D.C. motor amps
tdhorne Offline

Registered: 03/22/01
Posts: 344
Loc: Maryland, USA
Out of pure idle curiosity what was a monster like that turning.
Tom Horne
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison

#130715 - 01/07/07 03:18 PM Re: 1500HP D.C. motor amps
resqcapt19 Offline

Registered: 11/10/00
Posts: 2209
Loc: IL
The one I was working on is an extruder drive motor. That extruder is used for the final step for making ABS plastic pellets. The ABS resin and the addatives for color and other properties are fed into the extruder and and mixed and heated by the screws and forced out of the die head in about 130 3/16" strands that are then cooled in a water bath and sent to a pelletizer to cut them in to pellets about 3/16" long and then bagged, boxed or bulk shipped to the customer who will mold the plastic into a final product.
By the way those 8 535.3 kcmil DLOs were connected to 4 4/0s in the motor junction box. We had to add a box extension and a bus detail to make the transition from the size of wire required by the code to the internal motor armature leads.


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