Storage Batteries

[J Fimbianti]

article 480.6 is "overcurrent protection for "Prime movers"

what is the definition of a "Prime mover"

 

[Dennis Alwon]

I believe it is any equipment that converts energy from another source

 

[drcampbell]

In hybrid vehicles (including Diesel-electric locomotives), "prime mover" refers to the infernal-combustion engine, but the NEC doesn't apply to vehicles.

It sounds like 480.6 refers to batteries whose only purpose is starting infernal-combustion engines and are not tied into a building's electrical system.

 

[zbang]

Yep, "prime mover" refers to the engine/turbine turning an alternator/generator, or "the first thing that turns" in the system .

 

[raider1]

article 480.6 is "overcurrent protection for "Prime movers"

what is the definition of a "Prime mover"

480.6 permits batteries that provide power for starting, ignition, or control of a prime mover (Generator) to not have overcurrent protection for the conductors between the batteries and the starting equipment of the generator.

Chris

 

[ron]

Maybe I'm missing something but I don't see the words prime mover anywhere in 480.6.

 

[raider1]

Maybe I'm missing something but I don't see the words prime mover anywhere in 480.6.

Ron, I have pasted the 2017 NEC 480.6.

480.6 Overcurrent Protection for Prime Movers. Overcurrent
protection shall not be required for conductors from a battery
with a voltage of 60 volts dc or less if the battery provides power
for starting, ignition, or control of prime movers. Section 300.3
shall not apply to these conductors.

This was 480.5 in the 2014 NEC.

Chris

 

[ron]

Ron, I have pasted the 2017 NEC 480.6.

This was 480.5 in the 2014 NEC.

Thanks Chris, I have to get with the times.......

 

[publicgood]

Yep, "prime mover" refers to the engine/turbine turning an alternator/generator, or "the first thing that turns" in the system .

Agree.

NFPA 37: Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines

3.3.3  Engines. Prime movers such as internal combustion engines, external combustion engines, gas turbine engines, rotary engines, and free piston engines using either gaseous fuels or liquid fuels or combinations thereof.

 

[Sahib]

480.6 permits batteries that provide power for starting, ignition, or control of a prime mover (Generator) to not have overcurrent protection for the conductors between the batteries and the starting equipment of the generator.

Chris

It is a bit surprising that the code does not require it. In one incident I saw melting and smoking of 12V battery leads PVC insulation due to some short in the starter motor of a 30KVA generator.

 

[Dzboyce]

You can purchase starter motors for Diesel engines that have over current protection build into them. I havestarters with over current protection on some of my drilling equipment. It’s in the starter motor rather than in the wireing.

 

[drcampbell]

It is a bit surprising that the code does not require it. ...

I'm not surprised.
Getting a backup generator started might be more important than protecting its starter wiring.
A fault isn't likely to set the building on fire because a room containing an engine and fuel will be substantially non-combustible.
And there's a limited amount of energy in a battery. At some point, the battery will go dead and the overcurrent event will end.

 

[RumRunner]

There is s safety reason behind not having a protective device for conductors intended for starters or to initiate operation of prime movers, controls et al.
Starters only run in a few seconds. The power burst needed are also unstable especially when a few attempts failed where drop in battery voltage leads to rise in Amps.
I would hate to see an emergency power cells, battery banks unable to start a prime mover that would cause a life and death situation in an ICU (hospital) caused by a blown 50 cent fuse.

This is a territory of ASME and I'm sure they did a lot of thinking to come up with the idea.

 

[GoldDigger]

There is s safety reason behind not having a protective device for conductors intended for starters or to initiate operation of prime movers, controls et al.
Starters only run in a few seconds. The power burst needed are also unstable especially when a few attempts failed where drop in battery voltage leads to rise in Amps.
I would hate to see an emergency power cells, battery banks unable to start a prime mover that would cause a life and death situation in an ICU (hospital) caused by a blown 50 cent fuse.

This is a territory of ASME and I'm sure they did a lot of thinking to come up with the idea.

Where you cannot risk a loss of battery because of a marginal condition, the relatively simple alternative is to make sure that a short in the critical wiring cannot start a fire.
It does also make working on an energized system a bit hazardous.
I was told of a pair of tin-knockers working in a Telco CO installing an A/C duct. To get at the space they had to stand on the main bus bars of the 48V battery bank. No great shock risk there, but when they dropped the duct the middle section vanished and the two ends hit the floor. :angel:

 

[RumRunner]

There is no such thing as PERFECT DESIGN. You have to weigh the risk against the benefits.
We spent a lot time about compromise during our college days.