Myron Zucker, Inc. - Container Supply Company Case Study

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Container Supply Company - Garden Grove, CA

Most of us are aware of utility minimum power factor requirements and penalties charged unless power factor is maintained above the minimums. Another benefit of improving power factor that we recognize is the unloading of the transformer when capacitors are installed on the secondary distribution system. What many have forgotten is the basic fact that capacitors reduce the power usage from their point of connection in the electrical system back to the utility source. No load readings are changed from the capacitor point of connection out to the actual motors or equipment being serviced.

If a plant contains a quantity of large horsepower motors, a look at the concept of capacitor-at-load, that is, mounting the capacitors as close to the motors as possible, can prove beneficial. What does this method of capacitor installation accomplish? Installing the proper amount of total kVAR maintains a high power factor. The capacitors act "automatically", for each one is energized whenever the associated motor is energized. The transformer is unloaded in the same manner that an automatic bank accomplishes. Now come the additional savings. The capacitors have unloaded the complete distribution system. The feeders, the bus ducts, and the branch circuits are all carrying considerably fewer amperes. This leads to power savings, not just once, but year after year. I²R losses will occur in any electrical system. If they can be reduced, money will be saved. The amount of savings can be considerable.

After doing a careful facility analysis, a Myron Zucker sales engineer recommended that the plant engineer at Container Supply Company install fourteen capacitors on eight injection molding machines to improve the power factor and minimize I²R losses in the system.

The plant engineer took careful power measurements of each machine, as well as the total plant, with and without the capacitors energized. The readings were as follows:

PLANT-WIDE READINGS
BEFORE	AFTER
KW: 1643	kW: 1601
kVAR: 1295	kVAR: 924
kVA: 2092	kVA: 1849
PF: .785	PF: .866

A savings of 42 kW will result in an annual savings of $21,420. This is based on 6000 hours of operation times a cost of .085 per kWh. The initial investment cost approximately $5,800. The return on investment was 3.3 months.

The figure below shows the layout of the plant's electrical system. By installing capacitors directly connected to the load side of the starter contactors, the ampere reduction is occurring from that location all the way back to the meters. This reduction results in a smaller I²R loss (and kW reduction), and thus the $21,420 savings achieved. The most important point of this case is the realization that the company will benefit from these savings year after year.