Voltage Drop for 460V, 3 phase motor

[kwired]

Mmmmm, 460v appliances.

[h=5]Appliance.
Utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions such as clothes washing, air-conditioning, food mixing, deep frying, and so forth.

I really don't know why they put "generally other than industrial" in there.

If the thing is listed as a unit, self contained and all you need to do is provide supply conductors, it is an appliance per NEC regardless of supply voltage.

460 volt CNC machine that is one listed unit and all you need to do is provide a supply circuit - appliance or not?

460 volt blower motor that is part of a process line, has no local controller, and is custom fit into the process line - appliance or not?


[/h]

 

[Dale001289]

Appliance.
Utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions such as clothes washing, air-conditioning, food mixing, deep frying, and so forth.

I really don't know why they put "generally other than industrial" in there.

If the thing is listed as a unit, self contained and all you need to do is provide supply conductors, it is an appliance per NEC regardless of supply voltage.

460 volt CNC machine that is one listed unit and all you need to do is provide a supply circuit - appliance or not?

460 volt blower motor that is part of a process line, has no local controller, and is custom fit into the process line - appliance or not?

Lots of great thought process occurring on this thread. In reality, I'd probably have a hard time convincing Project these blowers are indeed, 'appliances', however, reverting to a previous comment, FLA and FLC are for cable ampacity - not for Voltage drop calcs. Thus I can confidently use nameplate FLA -

 

[kwired]

Lots of great thought process occurring on this thread. In reality, I'd probably have a hard time convincing Project these blowers are indeed, 'appliances', however, reverting to a previous comment, FLA and FLC are for cable ampacity - not for Voltage drop calcs. Thus I can confidently use nameplate FLA -

If the blower in question has it's own controls on it, it may be an appliance. But in an industrial environment it may be a factor assembly with the motor, but the starter and other controls are not a part of the unit - in that case not a appliance IMO.

 

[Dale001289]

If the blower in question has it's own controls on it, it may be an appliance. But in an industrial environment it may be a factor assembly with the motor, but the starter and other controls are not a part of the unit - in that case not a appliance IMO.

You are correct. The controller is located in the MCC, 2000+ feet from the motor. There are local controls provided by a HS (Stop) control station as well as multiple inputs from the vendor provided PLC and our DCS, I/O cabinets.

Great feedback. You guys are making me look good.

 

[templdl]

[h=5]Appliance.
Utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions such as clothes washing, air-conditioning, food mixing, deep frying, and so forth.

I really don't know why they put "generally other than industrial" in there.

If the thing is listed as a unit, self contained and all you need to do is provide supply conductors, it is an appliance per NEC regardless of supply voltage.

460 volt CNC machine that is one listed unit and all you need to do is provide a supply circuit - appliance or not?

460 volt blower motor that is part of a process line, has no local controller, and is custom fit into the process line - appliance or not?


[/h]

I guess what is the point? Yes, appliance or not. The inportant thing is what is the acceptable as applied via voltage at the point of usage. People get all hung up on percent voltage drop but what will the actual voltage end up to be at the point of utilization?
Even at the point of the service entrance the POCOs voltage one would expect to be at an acceptable value. If that varies so will the rest of the system. Then, will the voltage at the point where it is utilized considered going to end up to be we within and acceptable range?

 

[kwired]

I guess what is the point? Yes, appliance or not. The inportant thing is what is the acceptable as applied via voltage at the point of usage. People get all hung up on percent voltage drop but what will the actual voltage end up to be at the point of utilization?
Even at the point of the service entrance the POCOs voltage one would expect to be at an acceptable value. If that varies so will the rest of the system. Then, will the voltage at the point where it is utilized considered going to end up to be we within and acceptable range?

I agree. I also think most general use equipment is more tolerant to voltage drop then many think.

If you don't want the lights to dim when that one big motor starts, don't put them both on the same long feeder.

If it is 1500 feet from the feeder source, you might learn to live with the lights dimming when that motor starts.

 

[Dale001289]

I agree. I also think most general use equipment is more tolerant to voltage drop then many think.

If you don't want the lights to dim when that one big motor starts, don't put them both on the same long feeder.

If it is 1500 feet from the feeder source, you might learn to live with the lights dimming when that motor starts.

Lights wont dim when the motor starts, too much supply power behind them. At this plant, steam-driven generators produce 84MVA of power with large, power transformers downstream to numerous switchgear and MCC's.

 

[Ingenieur]

Can someone please answer, once and for all, should 460V be used or 480V? (using ETAP). Also, does Motor Service Factor (1.15) have to be considered?

imho
use 480 as the base supply voltage
460 is the rated motor operating voltage after some assumed drop
the SF does not need considered: not a normal operating condition (or should not be) and even if running at 115% a 3% drop will only increase marginally to ~3.5% or an additional 2.4 volts

 

[FountainGuy]

Ok. Here's another question, Ref 430.6(A)(1): Why does the Code insist on using the FLC's (Table 430.250) instead of nameplate FLA? We have a 60hp application at 460V. Nameplate says 68A. NEC says 77A must be used per the table. This causes the VD to kick the cable up one size. To me, doesn't make sense if the nameplate data is available, why not use it?

You size the motor protector based on the nameplate amps (and namplate S.F.). You size everything else based on NEC amps.

 

[templdl]

You size the motor protector based on the nameplate amps (and namplate S.F.). You size everything else based on NEC amps.

That seemed strange to me also but the way manufactures can manipulate their numbers by using the NEC amps everybody has to play be the same rules.

 

[templdl]

I agree. I also think most general use equipment is more tolerant to voltage drop then many think.

If you don't want the lights to dim when that one big motor starts, don't put them both on the same long feeder.

If it is 1500 feet from the feeder source, you might learn to live with the lights dimming when that motor starts.

It seems also that there are those who think things to death by thinking that this is an exact science. The same thing happens when it comes to determining fault current. It has to be determined where the raged edge is first before concluding that you may be in deep dodo. It is at that time that you should do a closer evaluation of you distribution system.
By using exact numbers such as an allowable voltage drop it removes the need to actually think, dumbing things down so to speak for those who don't understand actual applicstion requirements.