NEC definitions

[cmelguet]

Hi, I am trying to get my head clear around the following definitions. Can anyone specify the differences between the following devices to control motor in LV assemblies:

Motor controller,
Motor combination starter
Combination motor controller
self protected combination controller
Full voltage none reverse (FVNR) motor starter
Full voltage Contactor (FVC)

Which ones provide short circuit, overload and ground fault protection all in one unit, which ones required an additional Circuit breaker or fuse on the input, etc.
I understand these definitions change from country to country, so i want the North american definitions.

Regards,

 

[dpc]

"Combination" means the starter includes disconnecting means and short circuit protection (typically a circuit breaker or fused switch) in addition to the starter.

A starter is a contactor (or manual switch) plus overload protection.

Controller is a generic NEC term used for any type of motor control. A starter is a controller, but not all controllers are starters.

"Full voltage" is just referring to the starting method.

None of these provide ground fault protection unless it is specified to be provided.

 

[jraef]

And "self protected" combination controller just means that UL and the NEC had to come up with some sort of term for the little disposable IEC style motor protective switches, which are a disconnect, short circuit protective device, motor overload device and manual control device all in one. The term "self protected" means that they can be used in situations where there is a high available fault current, but they are not expected to be re-usable after a short circuit fault even, they will sacrifice themselves in the line of duty. Afterward, you through them away. In the more traditional NEMA design "combination motor starter" where you have a Molded Case Circuit Breaker as the SCPD, the MCCB is required to be re-settable and re-used. Hence the differentiation.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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[dpc]

I should have also pointed out that my definitions apply only in NEC and NEMA land. IEC-speak is probably different.

 

[jraef]

Well, the question was about NEC definitions so IEC would not apply anyway.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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[cmelguet]

Thanks, can you please check if i understand correctly:

Motor Controller: Any device that can start and stop a motor (this is from the NEC). ---From this I get i can use an instantaneous, or inverse time, circuit breaker, or a switch, but can not use a fuse.Correct?

Motor Starter: A controller with overload protection. ---- From this a motor starter is a inverse time CB, or a switch (contactor) with a time delay fuse, or a contactor with an overload protection. Correct?

Combination Motor Starter: Is a motor starter that includes Short circuit protection---I can use an inverse time CB, a switch with a time delay fuse, or a contactor with an overload and a fuse. Or by definition all this needs to be include in one big unit ?, so the only equipment that will fullfill the definition will be the CB with time delay? If all this came in one big unit isnt this a self protected controller?.

From my experience all this devices goes inside the MCC, so if i install a fuse, a contactor and an overload protection inside the module, can i call the module a Motor combination starter, FVNR for example?, but if i take the overload protection away i can call the module a FVC (Full voltage contactor) combination starter?.

Regards,

 

[dpc]

I don't know what an FVC is - never heard that term.

Starters do not have to be in an MCC - they can be separately mounted in their own enclosure or part of a control panel.

A controller does not have to be a circuit breaker. A contactor is a motor controller per NEC.

 

[jraef]

FVC = Full Voltage Contactor, not for motor loads. For example a resistive heating element.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376