Motor voltages in 430.250

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cppoly

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For a network voltage of 480V, the motor voltage listed in table 430.250 is 460V.

Does anyone know why they actually list 208V in the table as a motor voltage? 480V isn't listed, but 208V is. Trying to follow the voltage drop logic here so 208V seems strange to include if the table is trying to compensate for voltage drop.
 
I don't see the table as compensating for voltage drop, it is listing typical nameplate voltage.

It also includes a note saying "voltage ranges of 110 to 120, 220 to 240, 440 to 480, and 550 to 600 volts."

200 and 208 volts are not included in this note.
 
In an article on induction motors, it talks about NEMA motor voltage nameplate ratings. It says "Another misconception is to request a motor rated at network voltage, for example, at 480 V. The NEMA standard is 460 V. The voltage rating assumes that there is a voltage drop from the network to the motor terminals. Thus, the 460 V motor is appropriate on a 480 V network."

I was looking at 430.250 to see why the 460 V motor rating had a voltage drop taken into account but 208 V did not.
 
cppoly said:
In an article on induction motors, it talks about NEMA motor voltage nameplate ratings. It says "Another misconception is to request a motor rated at network voltage, for example, at 480 V. The NEMA standard is 460 V. The voltage rating assumes that there is a voltage drop from the network to the motor terminals. Thus, the 460 V motor is appropriate on a 480 V network."

I was looking at 430.250 to see why the 460 V motor rating had a voltage drop taken into account but 208 V did not.
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Clear as mud isn't it? Now consider the fact that even if the supply voltage is 480, it doesn't always mean it will drop to 460 at the load either. Around here 480 volt systems with little or no load often are measured right around 495-500 volts. But it is desirable to have voltage a little high instead of a little low for motors, and hopefully in worst case loading conditions that 495-500 doesn't drop much below about 470, even though down to 460 is acceptable.
 
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