1. 7154 VFD Presentation #4 May 2002 Paul Weingartner

2. Load types Standard motors High instantaneous current Lumber cutting example Lumber cutting example Fans, pumps

3. Utility billing Energy cost Demand charge Power factor (can be)

4. Energy cost (approx) Residential $0.07/kWh Commercial $0.06/kWh Industrial $0.05/kWh

5. Real-time pricing vs. Demand You can be billed either on a standard Demand type arrangement or, Pay the real-time demand cost

6. Real-time cost Supply and demand set the cost of power. The typical cost of $0.06/kWh can skyrocket to $4-5/kWh for short periods $1/kWh for hours

7. Energy rebate programs For larger customers that are willing to shed an agreed upon number of kWh during peak times, if requested by Cinergy to do so, will get a credit for energy they DON’T USE.

8. Demand

9. Demand charges

10. Demand charges 2

11. Rachet – min bill

12. Summer period

13. Look at what happened to California last year

14. Demand kWh

15. Power factor

16. Yearly billing info

17. Pump application w/o VFD Without a VFD, a pump usually runs at 100% speed Flow is controlled with a control valve A flow controller reads the flow rate from a flow meter and compares it against the setpoint

18. Runs at 100% The pump motor is running full speed Lots of wasted electricity $$$$

19. Assumptions – Assume __ That the motor in a non-VFD pumping application is using 75% of the nameplate power That Demand charges are not applicable Power factor is not an issue All cost will be Energy alone Motor efficiency =92%

20. Motor efficiency

21. 5 HP example – non VFD 5 HP x 746 W/HP = 3730 W 3730W / 0.92 (eff) = 4054 W 4054 W x 0.75 = 3040 W 3.040 kW * 8760 hrs = 26630 kWh 26630 kWh * $0.06/kWh = $1597

22. $1597 Almost $1600/year in energy cost for 7 x 24 operation

23. What is we used a low eff motor? Let the eff = 83%, then 3730 W / 0.83 = 4493 W 4493 W x 0.75 = 3370 W 3.37 kW x 8760 hrs = 29,525 kWh 29525 kWh x $0.06 = $1771/year Diff in cost is $174/year

24. 5 HP eff motor Premium Efficiency Motor, 5 horsepower, 1755 RPM, 230/460 volts Premium Efficiency Motor, 5 horsepower, 1755 RPM, 230/460 volts $448.25

25. 5 HP std motor General Electric Definite Purpose Motor, Rigid Base, Fan-Cooled, 3-Phase, Totally Enclosed, C-Face, 5 horsepower $381.25

26. Difference in cost between Std & Hi Eff $67

27. Pump Example with VFD Don’t need a control valve = -$1000 Need a VFD = +$500 Need a high eff, inverter rated motor = +$150

28. Less maintenance Control valves require more maintanence Hard to tell without added hardware how many strokes the valve has made Seals, etc

29. Less maintenance 2 VFDs provide diagnostics when problems occur

30. Energy cost Assume that if total usage is averaged that motor uses 33%

31. Fan basics Affinity law When the impeller diameter of a centrifugal pump is held constant the effect of changing the speed (RPM) of the pump is in accordance with the following: When the impeller diameter of a centrifugal pump is held constant the effect of changing the speed (RPM) of the pump is in accordance with the following: Capacity: Q1/Q2 = N1/N2 Capacity: Q1/Q2 = N1/N2 Head: H1/H2 = (N1/N2)2 Head: H1/H2 = (N1/N2)2 BHP: BHP1/BHP2 = (N1/N2)3 BHP: BHP1/BHP2 = (N1/N2)3 Q = Capacity, GPM Q = Capacity, GPM H = Head, Feet H = Head, Feet BHP = Brake Horsepower BHP = Brake Horsepower N = Pump Speed,RPM N = Pump Speed,RPM

32. Upshot Torque increases as a square of speed HP increases as the cube

33. Or look at it the other way If you reduce speed by 10% - new speed = 0.9 of old speed Torque = square (0.9) = ___ HP = cube (0.9) = ___

34. Centrifugal pumps http://www.pricepump.com/pumpschool/ps les.html http://www.pricepump.com/pumpschool/ps les.html