NEC

[rg1]

Two single phase 10 HP, 500V motors connected to a single branch. What is the  minimum size of  90 deg, THHW  conductor used if one motor is continuous and the other is intermittent duty cycle.

My problem is where to look for the fl current of a 10 hp 500v 1 ph motor. The table 430.248 does not have it? 

 

[knight1fox3]

Does it specify whether this is for an AC or DC motor? Because depending on that info will then dictate which table to use. My intuition and application experience leads me to believe this is a DC motor since 500V is a typical operating DC voltage. See Table 430.247.

 

[rg1]

Does it specify whether this is for an AC or DC motor? Because depending on that info will then dictate which table to use. My intuition and application experience leads me to believe this is a DC motor since 500V is a typical operating DC voltage. See Table 430.247.

View attachment 9470

From the question there are enough hints that these are AC motors. May be a wrong question? 

 

[knight1fox3]

View attachment 9470

From the question there are enough hints that these are AC motors. May be a wrong question? 

Certainly not enough detail provided in that case. However, I stand by my previous comment that this is most likely referring to a DC motor application. Which I suppose could be very loosely considered "single phase". LOL

 

[rg1]

Certainly not enough detail provided in that case. However, I stand by my previous comment that this is most likely referring to a DC motor application. Which I suppose could be very loosely considered "single phase". LOL

Have you taken into consideration that the motors are connected to a Transformer on a single branch.

 

[knight1fox3]

Have you taken into consideration that the motors are connected to a Transformer on a single branch.

Sure. But that doesn't necessarily mean that on the secondary side of the xfmr that the power supply isn't being rectified to DC. But again, it seems this problem is either worded incorrectly or has a typo.

 

[rg1]

Sure. But that doesn't necessarily mean that on the secondary side of the xfmr that the power supply isn't being rectified to DC. But again, it seems this problem is either worded incorrectly or has a typo.

Thanks a lot. I assume the actual examination questions are scrutinized thoroughly for such ambiguities.

 

[knight1fox3]

Thanks a lot. I assume the actual examination questions are scrutinized thoroughly for such ambiguities.

NP. And that is a correct assumption. Good luck with your studies! :thumbs:

 

[BigWheel]

View attachment 9470

From the question there are enough hints that these are AC motors. May be a wrong question? 

I'm inclined to believe that the "500V" was fat-fingered and was meant to be "200V." If it was supposed to be 200V, you could solve that with the NEC.

What's the solution given?

 

[Ship Wreck PE]

I would use the 460 volt column.

 

[BigWheel]

I would use the 460 volt column.

Problem is there isn't a 460V column in the single-phase table...

 

[rg1]

The answer is taking 500 V Dc. lol. @knight1fox3 was right but now its not worth to discuss the issue further.