Seamless UPS

Even UPS systems require routine maintenance, and that downtime spells risks for facilities that depend on clean, continuous power to protect equipment. A recent Caterpillar project in China – its first UPS project in the country – shows how this problem can be overcome.

Dr. Johannes Heidenhain (China) Co. Ltd. required clean, continuous power to protect its advanced manufacturing equipment from power disturbances and support its critical loads at the German-based company’s new plant in Beijing, China. As a manufacturer and assembler of optical and electronic components (including linear, angular and rotary encoders, as well as several measuring and inspection devices) for semiconductor and electronic equipment, maintaining a consistent factory environment overall – including air quality, temperature and power supply – is vital to Heidenhain’s core business. This meant not only ensuring continuous power to the manufacturing machinery, but also the ancillary temperature control and room cleaning control equipment in the space where the machinery is located.

For its new Beijing plant, Heidenhain recognized the need for a 24/7 continuous power system that would reliably condition power, while also providing protection from power failures, micro and macro outages, voltage sags and surges, and harmonic distortion – all of which could compromise the manufacturing process and result in inaccurate or damaged components. As such, the system would need to include an Uninterruptible Power Supply (UPS) that would work seamlessly and effectively with the generator set to deliver continuous power despite any disturbances or outages.


Figure 1. Dr. Johannes Heidenhain (China) Co. Ltd. required clean, continuous power to protect its advanced manufacturing equipment from power disturbances and support their critical loads at its new plant in Beijing
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Heidenhain Optics and Electronics, Ltd., in conjunction with German engineering company ED Zublin AG, approached Caterpillar Hong Kong to provide a continuous power solution that met pre-determined parameters originally specified to a competing product line. A Cat Electric Power consultant worked closely with Heidenhain’s local Caterpillar dealer, WesTrac China, to formulate a proposal that both met Heidenhain’s unique power needs and provided a clear advantage over other system providers. The simplicity of product design, structure, operation and maintenance requirements earned Heidenhain’s business as the single-source provider of a continuous power system for the new plant.

The solution

To deliver the established 500 kW of power support, Heidenhain’s contractor, ED Zublin AG worked with WesTrac to supply a Cat 3412 520 kW generator set and Cat UPS 750 kVA, the latter of which would be the first Cat UPS to be installed for commercial use within the People’s Republic of China.

“With a continuous power system running 24 hours a day, 7 days a week, intermittent maintenance becomes an inevitable factor,” said Zhu Jianming, senior sales engineer from WesTrac. “The Cat UPS provided a significant advantage over the competing product, a true rotary machine with a shaft between the motor generator and the UPS that requires the complete system to be taken offline for even routine maintenance.”

“The Caterpillar continuous power system is designed to allow the generator set to bypass the UPS and provide power directly to the low voltage distribution system in the event of the UPS needing to go offline,” explained Jack Shu, Caterpillar EP consultant in Beijing. “That way, something like a simple bearing change in the UPS does not affect continuous operation of the remainder of the system.” The Cat UPS’ integrated flywheel energy storage design is of critical importance in the plant’s operation. In addition, its high power density and small footprint allowed for the unit and a Cat 520 kW generator set to be installed in a small 12 m by 4 m space inside the room in which the actual equipment is located.


Figure 2. The 750 kVA UPS was the first Cat UPS to be installed for commercial use within the People’s Republic of China
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The Automatic Transfer Switch (ATS) connects the Cat UPS and generator set. The ATS is additionally connected to the utility power. In the event of power loss, energy is derived from the flywheel of the UPS to provide uninterrupted power to the critical load at nominal voltage. The ATS will simultaneously send a signal to the generator set for automatic start-up. When power from the generator set is available, the UPS synchronizes the output and input voltages and transfers the load to the generator set. During the whole process, power supplied to the critical load is protected and clean continuous power is the result.

Up and running

Installation of the Caterpillar continuous power system was completed at the site in 2005 and the whole plant was handed over to Heidenhain. Since the installation was completed, several tests have been conducted, including planned shutdowns of the utility power.

“After much testing, the Cat UPS, generator set and ATS equipment have all proven their mettle,” said Zhu Jianming. “These tests have demonstrated that the Cat 3412 generator set starts up in less than 8 s, with the Cat UPS providing successful ride-through beforehand. In monitoring the sensitive machinery during the continuous power system testing, there has also been no evidence of a disturbance or failure upon shutdown of the utility. As such, Heidenhain has expressed confidence that the system will perform as intended when it goes online full time once construction is finished and operations are running at the plant.”

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