10333 Air Compressor System

Project Type: Training Facility Summer 2011

Summary & Goals

Customer provides skills training at their facility that requires the use of compressed air. A large OEM compressor package was ordered and installed in 2010. It has never operated correctly in their facility and the manufacturer and sales reps had blamed the customer on an improper main power feed to their building. Customer wanted another opinion and hopefully a solution that did not involve a power service upgrade.


The customer had worked with the sales representatives and manufacturer for over a year in trying to resolve the issue of their compressor never functioning. The blame was being placed on the customer’s insufficient building power service. As a result, the customer contacted Logicon for outside engineering services.

The air compressor package was fed by a 208:480 3ph 225KVA transformer. During startup, the motor draw would cause the main voltage to dip from 488 VAC to nearly 400 VAC. This resulted in a drop on the internal 480:120 control power transformer secondary from 128 VAC to 100 VAC. This low voltage caused a rapid chatter of the coil never fully sealing in and allowing the motor to ramp up to speed. The coil of the main starter for the compressor motor had a manufacturer’s range of 95-180 VAC. The fluke meter used obviously was not accurately showing us the true voltage at the coil but it was a close enough indication of the issue at hand.

To maintain the 120 VAC during the dip in voltage during startup, a constant voltage power conditioner was installed in line with the existing 120 VAC feed of the control transformer to feed the controls on the machine. This power conditioner was capable of maintaining the 120VAC power output even when faced with a 20% loss of line voltage. This allowed the proper voltage level to be passed to the coil of the starter and for the compressor system to properly ramp up to speed with zero chatter in the starter.

Customer is currently utilizing their new functioning air compressor for the first time in over a year.


Logicon performed an on-site inspection of the machine and found that the issue was simply related to a significant drop in line voltage during the startup of the machine. This prevented the main starter contact from pulling in sufficiently. A constant voltage power conditioner was added to the 120 VAC control power to maintain the coil voltage during startup. This eliminated the startup issue completely and at a fraction of the cost a new power service would have cost.

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