MGE knows its UPS ABCs

MGE UPS Systems has introduced three new versions of uninterruptible power supplies under its Comet product name. Rated at 100, 125 and 150 kVA, the higher-range versions of the three-phase Comet UPS family will be available Aug. 1, supplementing three smaller models released earlier this year.

The Comet line boasts a 95% efficiency rate for backing up network systems, computer equipment and other peripherals. The UPS configuration features a solid-state inverter, rectifier/battery charger, continuous-duty static switch, and an internal maintenance bypass switch and battery plant.

The microprocessor-based Comet features self-testing and self-diagnostics, and it alerts users to all UPS activity via controlled firmware. Comet supports all standard voltages and is available in a free-standing or adjacent battery cabinet.

Southwestern Bell is one notable user of the Comet UPS family, according to Mike Lasky, three-phase product manager for MGE. "They back up a lot of their telephone switching equipment," Lasky said.

MGE UPSs are line-interactive, which is important in places where brown-outs, spikes and surges are prevalent. "Especially in Southern California, very rarely do we get a major blackout," Lasky said. "But a sensitive, two-way piece of equipment may shut off" in a brown-out.

Line-interactive UPSs constantly monitor equipment on-line and adjust the power supply accordingly. "You could go as low as 98 V input and still produce 120 V," said Barry Eisenberg, product manager for single-phase UPSs at MGE.

Such line-regulating capabilities are also available in other MGE UPSs designed for smaller applications. For example, the Pulsar ESV family of UPSs, introduced this spring, is primarily targeted at Internet and intranet applications that require extended battery capabilities. The ESV17 is rated at 14 minutes of backup time at 100% load and 40 minutes at 50% load. The ESV20 provides 11 minutes of backup power at 100% load and 30 minutes at 50% load.

The Pulsar ESV also can operate in a low-lying voltage situation indefinitely, without resorting to battery backup, Eisenberg said.

All ESV models feature an automatic battery tester. "Coupled with the automatic battery test, we have a front-panel alarm that tells you that the battery needs to be replaced," Eisenberg said. "We know historically that 50% of all UPS failures are because of batteries.

The Solution Pac '97 power management software also complements the intelligent capabilities of MGE's new generation of UPSs. The software enables users to perform high-power communications with the host equipment, essentially monitoring what the UPS is doing, Eisenberg said.

The Solution Pac driver allows the user to tailor the ESV parameters for a particular environment. For example, the Pulsar ESV can be programmed to perform automatic system diagnostics once a week, or more or less frequently, he said.

After introducing its first power meter nearly 50 years ago, Hewlett-Packard recently announced a new generation of power sensors and meters incorporating digital signal processing and advanced microwave semiconductor technology. The new power meters are available in a single-channel model, the HP EPM-441A, and a dual-channel model, the HP EPM-4442A. The HP ECP-E18A model continuous wave power sensor operates between 10 and 18 GHz. For operation between 50 and 26.5 GHz, HP offers model HP ECP-E26A.

A sensor and the HP EPM-441A power meter provide manufacturers with measurement speeds of up to 200 readings per second. The meters and sensors eliminate or reduce range-switching delays because the combination has only one fast switch point across the 90 dB dynamic range.

For research and development, instrumentation absolute accuracy is specified at 0.02 dB in logarithmic mode and -0.5% in linear mode. The sensors' calibration factors are computed at HP facilities and stored in electrically erasable programmable ROM. In that way, the calibration factors are automatically downloaded into the power meter when the sensor is connected. Users don't have to key in the data, so there is little room for user error. For configuration, the power meters feature hard keys for frequently used functions and softkey menus. Users can save and recall up to 10 configurations.

Front- and rear-panel bumpers protect the power meters during field use. Each power meter weighs nine pounds, and features a bail handle for carrying. The meters have high-resolution LCDs with LED backlighting and contrast control so users can see readings from a distance and in several lighting conditions.