Bryan UnderwoodAdvisor: Prof. Gutschlag

Alternating Current Power Factor Monitoring and Correction

Power Factor is the ratio of the active power to the apparent power

P.F. = = VI

VI )cos(* S

P

Complex Power Diagram

Poor power factor is due to inductive loads such as induction motors in air conditioners and refrigerators

A very low power factor usually results in the power company charging more on a utility bill

Ameren Illinois requires Residential customers (rate DS-1) and Light Industrial Non-Residential customers (rate DS-2, DS-3) to maintain a power factor of 0.90 while Heavy Industrial Non-Residential customers (rate DS-4) must maintain a power factor of 0.951

If the power factor falls below the minimum specified by Ameren and ComEd, they require corrective devices to be installed

Pacific Gas and Electric (PG&E) charges 0.6% more on a utility bill for each percentage point below a power factor of 0.852

About 60% of the electrical load in the United States is due to AC electric motors3

According to the U.S. Energy Information Administration (EIA), only about 25,000 out of 200,000 manufacturing companies participate in power factor correction (PFC)4

Increased I2R losses in transmission lines due to the additional current requirements needed to provide excess reactive power reduces efficiency, capacity, and profit margins

Increased current requirements result in higher transmission line, transformer, and switch gear current ratings

Usually done by capacitor banks◦ Generate “negative” reactive power

http://accessscience.com/content/Reactive-power/802370

Hampden Type WRM-100 3-Phase Motor 220 V 1.4 A 1725 RPM 1/3 HP

SATEC PM172E-N 3-Phase Programmable Power Meter

SATEC Power Analysis Software V1.4 Build 5 Configure basic setup of meter, set trigger points, and view event

logs and waveforms

news.thomasnet.comdirectindustry.com

Larger meters have more relay inputs and outputs to permit more incremental values of capacitors to be switched as needed for more precise control of the power factor

More programming options provide more robust control for better power factor correction

Potter & Brunfield KRPA-11AG-120 Power Relays

Capacitance is added to each line and can be varied from 1.6uF to 50uF

Resistors are placed in series with the capacitor banks to reduce inrush currents

][8.4][25

][120A

VI

Current through resistorwith 10uF Capacitor

Power losses

Current w/ 20uF

Power losses

Current w/ 30uF

Power losses

][6159.84450395.06159.84433.266

0120AI

][07139.525*)450395.0( 22 WRIP

][3252.79889119.03252.79965.134

0120AI

][7633.19 WP

][2121.7430597.12121.748857.91

0120AI

][639.42 WP

Relay coils are energized from SATEC meter when the power factor drops below a certain point◦ Line current is also monitored to ensure no switching occurs when no load is

present

Capacitors are added to the circuit in parallel with the motor◦ Placed in parallel to maintain the same line voltages into the motor

Power factor can be varied over any desired range to avoid electric utility company charges

Project system maintains a power factor of above 0.98

Experimental Results

-0.9

Complete the theoretical circuit model and compare with experimental results◦ Research how the meter calculates its values

Write tutorial on how to use power meter◦ Will use as an appendix for final paper

Write final paper

1 http://www.ameren.com/sites/aiu/Rates/Documents/AIel14rtds4.pdf

http://www.ameren.com/sites/aiu/Rates/Documents/AIel48rdimf.pdf

2 http://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/power%20factor--revised-8-9-07.pdf

3 http://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/power%20factor--revised-8-9-07.pdf

4 http://www.eia.gov/emeu/mecs/mecs2002/data02/excel/table8.1_02.xls

Motor Load

Apparent Power (VA)

Power Factor

Active Power (W)

Motor Speed (RPM)

No Load 345 0.312 107 1777

¼ Load 354 0.435 156 1705

½ Load 394 0.554 216 1683

¾ Load 419 0.658 276 1677

Full Load 520 0.776 405 1585