Rockwell Automation 150 MNL/SMC DIALOG+/APP-PROD GUIDE - Manual (Page 141)

SMC Dialog Plus Controller Special Application Considerations 5-17
Application Requirements
Savings in energy costs are possible in certain applications. Figure
5.13 shows test results of actual motors. Figure 5.13 was developed
using 10, 50, and 125 HP motors.
Based on these test results and other data, there is very little savings
possible above 50% load. A curve of maximum theoretical savings
can be drawn using the theoretical savings of 50% of the losses and
the data which indicates little or no savings above 50% load. This is
illustrated by the upper curve in.
In reviewing the test data for lower limits, it could be estimated that
20% losses are saved at no load, and no losses are saved at 20% load.
This is illustrated by the lower curve in Figure 5.14.
Figure 5.13 % kW Saved vs. % Rated Load Figure 5.14 Estimated Energy Savings
Preliminary Estimates
A simple “full load-no load” preliminary estimate for the application
of an energy saver can be made by using the following procedure:
1. Convert horsepower to kilowatts.
2. Determine the total kilowatts used by the motor by dividing the
horsepower kilowatts by motor efficiency.
3. Determine the motor losses by subtracting converted horsepower
kilowatts from total kilowatts.
4. Calculate the maximum theoretical savings in kilowatts by multi-
plying motor losses by 0.50.
5. Determine kilowatt-hours saved by multiplying the maximum
theoretical savings in kW times the number of hours per year the
motor is operated at no load.
6. Maximum theoretical savings dollars can then be determined by
multiplying kilowatt-hours saved times the cost of electricity per
kilowatt hours.
60
50
40
30
20
10 20 30 40 50 60
% Motor Load
% kW
Saved
10
50 HP
10 HP
125 HP
60
50
40
30
20
10 20 30 40 50 60
% Motor Load
%
Losses
Saved
10