Cummins Power Generation Transfer Switches First with UL-Listed 30-Cycle Ratings

MINNEAPOLIS- Series OHPC and CHPC PowerCommand® automatic transfer switches from Cummins Power Generation Inc. are the industry's first transfer switches to achieve UL-listed 10-cycle and 30-cycle withstand and closing (short-time) ratings.

The OHPC open transition and CHPC closed transition switches demonstrated unprecedented short-time ratings of 25 kA at 10 cycles for 125 to 260-amp switches, 30 kA at 30 cycles for 300 to 600 amps, and 42 kA at 30 cycles for 800-amp switches in UL tests. The switches continued to operate safely at full load, even after testing.

The UL listing provides consulting and specifying engineers independent assurance that the OHPC and CHPC transfer switches offer the industry's highest performance level, particularly for standby power systems requiring selective coordination.

As defined by the 2008 edition of the National Electrical Code (NEC), selective coordination is mandatory for emergency and legally required electrical systems in buildings where life safety is paramount, including hospitals, health care facilities, emergency shelters and high-rise buildings with multiple elevators. NEC 2008 also requires selective coordination for critical operation power systems (COPS) in secure buildings such as banks, data centers, embassies and government offices.

Selective coordination localizes an overcurrent condition to restrict outages to the circuit or equipment being affected. It is achieved by selecting circuit breakers and transfer switches with timing and withstand characteristics that delay or prevent faults from tripping upstream overcurrent protection devices. Selective coordination requirements are more easily satisfied by specifying OHPC or CHPC switches rather than products without UL-listed short-time ratings.

The ability of CHPC and OHPC transfer switches to withstand fault current for up to 30 electric cycles (one-half second) gives the consultant the flexibility to adjust the instantaneous time delay on the ATS overcurrent protection device to prevent upstream breakers from tripping unnecessarily.

Both transfer switches feature Cummins Power Generation's innovative High Endurance Mechanism (HEM), designed to ride through a fault condition undamaged and retain its capability to carry 100 percent of the rated load. Magnetic forces developed during a fault cause a typical transfer switch's contacts to blow open, producing an electrical explosion that often results in extensive internal damage to the switch, requiring replacement of contacts, arc chutes and, in some cases, the controller.

In contrast, the HEM uses that same magnetic energy to hold the contacts closed during a fault, virtually eliminating arcing, contact damage and performance degradation. It can survive multiple faults of the specified magnitude - listed on the nameplate as the withstand and closing current ratings (WCR) - and continue to carry the rated current without overheating. This proprietary Cummins Power Generation technology means that there will be no costly repairs or inconvenient downtime after a fault.

"Cummins Power Generation is proud to be the first manufacturer of transfer switches proven to survive a fault condition and to continue to operate at full load without repair," said Rich Scroggins, ATS product manager, Cummins Power Generation. "This ability gives consulting engineers more design flexibility in addressing requirements, and potentially to lower costs by using fewer transfer switches."

Underwriters Laboratories (UL) is a leading safety testing and certification organization that has conducted product safety testing for nearly 115 years. On electrical products, the UL mark designates products that have been certified for safety regarding foreseeable hazards that include electric shock, fire and mechanical hazards.

Cummins Power Generation, a subsidiary of Cummins Inc. (NYSE: CMI), is an industry leader in introducing advanced low-emissions power generation solutions around the world. With over 80 years' experience, the company's global distributor network delivers innovative, reliable and cost-effective solutions for any power need - commercial, industrial, recreational, emergency and residential. Products include temporary or permanent pre-integrated power systems, combining generator sets and power control and transfer technologies. Services range from system design, project management, financing, and operation and maintenance contracts to development of turnkey power plants.

For more information, contact Robin Reid, Cummins Power Generation, 1400 73rd Ave. NE, Minneapolis, MN, 55432. Phone: 763-528-7849; Fax 763-574-5298. Or visit

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