Eric,
In the mean time I have asked several professional engineers and some inspectors, and they told me that nothing escapes the requirement of 110.14(c) in that the ampacity of the circuit is limited by the ampacity of the termination which is based on the rating for the particular wire size...
So article 590 allows the terminating of flexible cable using lugs instead of using an attachment plug.
Assuming using a type-W #4/0awg cable and terminated at a 75 degree lug on a breaker: The 90 degree C rating of the cable is 405A, but per 110.14(c) the ampacity of the termination must be...
I have a few NEC code questions that I have not been able to have answered to my satisfaction yet, and I am hoping some of you code experts can help me out.
Background:
My company routinely uses #4/0 AWG single-conductor type-W cables and smaller (#6, #4, #2 AWG) multi-conductor type-SOW...
If you use a soft starter you will probably want to use one with a current ramp function. A VFD would probably be the best option technically speaking, but you'll have to work it out from a cost standpoint. You'll be able to dramatically reduce the generator size using a VFD to start your...
I size diesel gensets for motor starting applications daily. Without having manufacturer's full data (speed-torque/current/power factor motor curves plus speed-torque load curve plus moment of inertias of motor, coupling, gearbox, load, etc.) you can't perform an accurate motor acceleration...
Electricpete,
We will be performing a full voltage uncoupled run on the motor, and I need to size my distribution components so that they can handle the motor's no-load current. The motor will be run by a 480V generator through a step-up transformer. I was trying to figure out a way to start...
Edison123, we'll be using a generator as a soft-starter most likely, but I was trying to determine if we could just start it D.O.L. using a the generator at full voltage. For that approach we'd use a "choke" transformer that would limit the current drawn from the generator. To do that though I...
Guys & Gals,
We have a 2000 HP, 292 RPM (24-pole induction), 4160V, 60Hz circulator motor on a test stand. It's an Allis Chalmers motor and is probably 30-40 years old.
I am trying to figure out some ballpark numbers for the no-load current and the rotor moment of inertia. Do any of you have...
I agree with everyone saying your 495V is not a likely cause of your motor overload relay tripping. It is quite common for 480V-nominal systems (with 460V motors) to run as high as 500V without causing any motor overload issues. If you have a overload heater relay, you may have problems with...
Our local natural gas utility company has recently installed a metering station and a pipe 4" in diameter and the pressure regulator is set to 5psig. We are supposed to hook up a flexible pipe from the utility pipe to our natural gas generator. My gut says this meets the NEC definition of...
Thank you guys.
Is there some sort of official document by NFPA or other group that explains these sizing requirements (especially the termination requirements of 110.14(C)) in detail and gives examples like you have given?
Our business group is going to have a hard time with this, so it would...
We are using #4/0 AWG dual rated "type-W/RHH" flexible power cable on a job. The manufacturer's data sheet lists the cable as rated 405A @ 90C based on NEC table 400.5. We will be terminating the cable to a power terminal block rated 75C. The cable is going to be installed in an uncovered...
