[RE-wrenches] 10 HP mtr

[Mick Abraham]

Motor math can be fun!

If the motor is 50% efficient, begin with 1 horsepower = 746 watts, so 10
horsepower = 7,460 watts but that would be at (the impossible) 100%
efficiency.

Now apply the efficiency factor: 7,460 watts/.5 efficiency assumption =
14,920 watts (simplified down now to 14.9 kilowatts)

14.9 kW x 24 hours = 358 kilowatt-hours that must be offset per day.
Multiply by 30 to get 10,740 kilowatt-hours that must be offset per month.

If the motor efficiency is different than 50%, start over but follow the
same mathematical pattern.

Note: a motor that is rated for 10 horsepower may or may not actually be
delivering 10 horsepower at the shaft. If the torque/RPM requirement for the
pump is less than 10hp the motor will follow the load and the motor's power
requirement will be lower.

Best idea: wait until the pumping system is installed and running, then
measure the amperage and do math from there. OR: try to get a kilowatt-hour
meter installed ahead of the pump motor and just read the kWh after one day,
seven days, or a month.

Jolliness,

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675


On Fri, Nov 6, 2009 at 4:05 PM, Max Balchowsky <max at seesolar.com> wrote:

> I have a request to install an array to offset the usage for a 10 HP
> irrigation pump that I'm told is going to run 24/7 in PG&E territory,
> what do you motor guys know about the usage I should  expect..........
>
> Max Balchowsky
> SEE Systems
>
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