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#24743 - 04/22/03 10:43 AM energy savings?
Reel-Break Offline
Member

Registered: 04/04/02
Posts: 179
Loc: nc
Can anyone help me find approx. dollar savings in the following situation.We have a bbc motor wired delta 220v 3ph pulling 60 amps.We rewired the motor Y 380 3ph and the load amps droped to 28amps.Before the motor was running on an older drive. Now we changed to a toshiba h3 transitor inverter.The motor is a 37kw.This came up in conversation but I`m not sure how to calculate the savings if there is any.Thanks in advance for any assistance you may have.

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#24744 - 04/22/03 02:43 PM Re: energy savings?
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
Real Break:
Watts (KWHr) are the same, irregardless of voltage and amperage.
THere may be a savings if the demand (KW) is reduced by the new drive.
There are also some savings if you have a new high efficiency type motor. The basic calc for watts (KW) times time, will give you the base answer. As to the efficiency, the code letters, and the nameplate info should give you the data for that.

John
_________________________
John

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#24745 - 04/24/03 04:02 AM Re: energy savings?
mlk682 Offline
Member

Registered: 04/14/03
Posts: 46
Loc: Foley Mn
Dollars Savings Per Year =
0.746 x HP x [(1/EffA) - (1/EffB)] x hours x $/KWh

Where:

HP = load on the motor
EffA = efficiency of motor A at HP (expressed as decimal)
EffB = efficiency of motor B at HP (expressed as decimal)
EffA < EffB
Hours = hours of operation under load
$/KWh = average cost of electricity per kilowatt hour

The one large dynamic you have done is changed your power factor by raising the voltage . In doing this you have directly effected your motor efficiencys hence the savings.

Mike

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#24746 - 04/24/03 01:41 PM Re: energy savings?
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
There are {however “rosy”} examples at energy.copper.org, but the savings for one motor is probably not worth running the calculations. Losses in the drive probably offset any conductor savings. One somewhat related discussion is http://www.lmphotonics.com/energy.htm

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