motors of different voltages

[rey-man]

Will motor pumps of the same horsepower but different voltages have the same efficiency?

thanks.

 

[Chamuit]

I would think not.

 

[ActionDave]

Yes or no. Motor efficiency is based on how the motor is manufactured. A motor running on higher voltage will use less amps but power is the same, 10A at 480V is the same as 20A at 240V. The voltage that each set of windings sees is the same at either voltage.

 

[Ingenieur]

If they are sized properly head/Q vs the system curve, yes, very close

 

[drcampbell]

For a typical industrial 230/460-volt motor, the windings are connected either in series (high voltage) or parallel. (low voltage)
The current through, and voltage across, each winding is precisely the same whichever way it's hooked up.

Likewise for motors which can be configured for 115 or 230 volts.

The only difference in efficiency will come from external factors. The voltage drop might be more in the feeder, or power might have to pass through one more transformer, for example

A motor designed for 240 volts might not be as efficient on 208 volts, and will probably have a smaller service factor, but that depends on the details of the individual motor's design much more than which voltage is selected.

​

 

[Ingenieur]

There are 2 components to pump eff
the motor, range ~0.90 if sized properly
the pump, 65-70% perhaps at it's optimum point
often they do not overlap
The pump max eff may be at 70% flow and the motor is only at 75% load
typically a motor is more eff closer to 100%, but the pump is not
a balancing act

say the pump eff is 70
motor 1 85
motor 2 90

overall 1 = 0.70 x 0.85 = 60%
overall 2 = 0.70 x 0.90 = 63%

so you have a 5/85 or 6% more eff motor the pump is only 3/60 or 5% net more eff
the pump eff can easily mask any motor eff
and this assumes the pump is sized properly, which is seldom the case
bigger isn't better in this case lol

 

[Sahib]

Another factor is the maintenance of the overall efficiency during the working life of a pump. It decreases over time unless there is proper maintenance.

 

[Sahib]

Will motor pumps of the same horsepower but different voltages have the same efficiency?

thanks.

No if one motor is single phase and the other motor is three phase even with same voltage magnitude and same HP.

 

[kwired]

No if one motor is single phase and the other motor is three phase even with same voltage magnitude and same HP.

That does not automatically mean a three phase motor is more efficient then a single phase motor of same HP rating either, as is often presumed to be.

 

[Sahib]

That does not automatically mean a three phase motor is more efficient then a single phase motor of same HP rating either, as is often presumed to be.

Well which 3 phase IM (design A B C ....) has rated efficiency lower than 86%?

 

[rey-man]

No if one motor is single phase and the other motor is three phase even with same voltage magnitude and same HP.

can you please elaborate more Mr. Sahib?

 

[Saturn_Europa]

That does not automatically mean a three phase motor is more efficient then a single phase motor of same HP rating either, as is often presumed to be.

That has always been my assumption. For a three phase system watts = root mean square * volts * amps * pf

For a single phase watts= volts * amps * pf


for a given amount of VA a three phase motor would always have a higher wattage output. What am I missing.

Thank you for the clarification.

 

[Ingenieur]

That has always been my assumption. For a three phase system watts = root mean square * volts * amps * pf

For a single phase watts= volts * amps * pf


for a given amount of VA a three phase motor would always have a higher wattage output. What am I missing.

Thank you for the clarification.

You are comparing 3 ph to 1 ph
the 3 phase has MORE va, the sqrt of 3 times more
current and voltage is the same, but S and P are not

a better eval imo is 2 pumps of the same wattage/power but different voltages being compared
look at the Q each moves
the one that moves more for the SAME power is more eff

but again, too many variables to be definative

 

[Sahib]

can you please elaborate more Mr. Sahib?

NEMA MG standard does not recognise single phase IM for energy efficiency. Energy efficient IM are 3 phase. Efficiency for 1 phase IM varies from small size to large size, maximum 86% at 10 HP.

 

[kwired]

NEMA MG standard does not recognise single phase IM for energy efficiency. Energy efficient IM are 3 phase. Efficiency for 1 phase IM varies from small size to large size, maximum 86% at 10 HP.

That might be one reason you would find more efficient 3 phase motors then comparable single phase motors as a general rule, especially in newer models.