Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

parallel feed to DC motor

Status
Not open for further replies.
resqcapt19

resqcapt19

Electrical
Joined
Aug 29, 2001
Messages
536
Location
US
I'm going to be installing a large DC motor that will require that the armature leads be installed in parallel from the drive to the motor. Can I install the 3 positive leads in one conduit and the 3 negative leads in the second conduit? The conduits will be rigid steel. I know that you can't do this on AC systems because of the inductive reactance. I don't think that is a problem on a DC system. If I can install the positive in one and the negative in the second conduit, I can save 2 conductors. If I must place the positive and negatives in the same conduit, the circuit will require 2 positive and 2 negative in each conduit because of the derating required for four current carrying conductors in a raceway.
Don(resqcapt19)
 
Sort by date Sort by votes
I say yes, you want to make sure all parallel conductors are the same length and preferably free of splices.
 
Upvote 0 Downvote
The derating for current carrying conductors applies wether the same polarity cables are run in the same conduit or not. Therefore the desicion to run all the positive leads in one conduit and all the negative leads in a second will not effect the conductor sizing or quantity.
 
Upvote 0 Downvote
When conduits are run in parallel, they must be matched. I can't put two sets in one conduit and one set in the second conduit. Also when I put 2 sets in one conduit the derating requires larger conductors. If I can place all of the + in the first conduit and the - in the second conduit, only 3 conductors will be required in each raceway and derating will not be required.
Don(resqcapt19)
 
Upvote 0 Downvote
In the ’99 NEC, It seems like article 300-20 [Induced Currents] is specific to alternating-current circuits, but articles 300-3 and 310-4 *are not.* Specifically, as I understand it, 300-3(b)(1) [Paralleled Installations] does permit the arrangement you describe in any instance (whether DC or AC).
 
Upvote 0 Downvote
Correction: 300-3(b)(1) [Paralleled Installations] does NOT permit the arrangement you describe.
 
Upvote 0 Downvote
Busbar,
Thanks. I miised that point in 300-3(b)(1). However, I still have the question if the circuit that I have proposed will cause any problems. The code is not an issue in this installation.
Don
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Joel_Lapointe
  • Locked
  • Question Question
Small dc brushed electrical motor format "280"?
Replies
4
Views
4K
edison123
edison123
PaulKraemer
  • Locked
  • Question Question
DC motor that was exposed to foreign substance is surging
Replies
6
Views
4K
waross
waross
CB333
  • Locked
  • Question Question
12V DC Motor in Light Fixture with Dimmer & 12V DC to 110V AC Inverter
2
Replies
22
Views
2K
BrianPetersen
BrianPetersen
Pratik jain
  • Locked
  • Question Question
Replacing DC motor with induction motor & vfd
Replies
5
Views
1K
Gr8blu
Gr8blu
R
  • Question Question
Testing a 100HP Vertical Motor
Replies
5
Views
10K
waross
waross

Part and Inventory Search

Sponsor

Back
Top