motor starter/conduit size

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lew3611

lew3611

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hey guys, by the way long time no here and I am glad to be back!

Anyway, I took an exam today for a potential job and was asked several questions on the spot and none were multiple choice. I will write the questions and seeif you guys have some ideas for answers.

(1) State the size of a starter, breaker, conductor, and conduit for a 10 hp 480 vac motor?
( my answers were starter:35amp; breaker:20amp; wire:12awg; and conduit:1\2" emt.)

(2) explain a full wave rectifier?

(3) draw a 3-wire start/stop control circuit (control voltage =110)

(4) what does SAE mean on nuts/bolts?
(my answer was Standard American Engineering?

tahnks guys.
 
Re: motor starter/conduit size

1. I have no idea.

2. A full wave rectifier converts an AC sine wave into DC.

3. I will do my best to explain this one without a drawing. A 3 wire start stop has one normally closed button (stop) connected in series with a normally open button (start). The memory contact is in parallel with the start button. The output of the buttons/memory contact is connected to the coil and overload contact in series.

Logic: If not S1 and (S2 or C) then C

4. I don't know that one either.

Looks like I failed. :(
 
Re: motor starter/conduit size

Peter don't feel bad I thiought the majority of them were vague questions anyway :confused: Well, do you know of a site where I can actually see the drawing? It would really help. Thanks buddy!
 
Re: motor starter/conduit size

1. The starter is sized to the hp of the motor
Then you size the "heaters" accord. to protect the moter
2. conductor sized to the ((hpx746watts)/voltage)x1.25. Dont forget you can only load a circuit to 80%
3. conduit sized for Fill per code.
4. Full Wave Rectifier converts the negative half wave of an alternating current into a positive half wave (a/c to d/c)
5. SAE is nothing more than a standard.
1/4-20 1/4 inch bolt- 20 threads per inch
and so on......

[ February 23, 2005, 10:12 PM: Message edited by: bigjohn67 ]
 
Re: motor starter/conduit size

1. Starter: Nema Size 1
breaker: 35-ampere
conductor: #14 @ 75?C
conduit: What type?

2. AC to DC converter

3. L1 to NC stop, to NO start, holding contact in parallel with start, to magnetic starter coil, to neutral.

4. Society of Automotive Engineers?
 
Re: motor starter/conduit size

S.A.E. are the standards developed by the Society of Automotive Engineers.
 
Re: motor starter/conduit size

I agree with bph post of 10:12PM.

On #3 I might add that, of course the N.C. overload relay contact is in series with the rest of the control ckt. This is usually a "factory wire" already on the starter.
 
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