Out in Front: March 1, 1996

If you're tired of worrying about milliwatts and microamps, take heart: Some applications require serious power. These include adaptive magnetic bearings, active vibration-canceling and shock-absorber systems, beam steering, subaudio sonar, and motion control. The Model 262PN wideband PWM amplifier from Copley Controls provides ±300V at ±85A continuous and ±177A peak output. A high-efficiency, low-cost design makes the amplifier look like a linear device to the load but with the benefits of a PWM architecture switching at 51 kHz. The output is stable with magnetic-coil loads, which require high voltage to establish current flow and lower voltage to maintain the current level. You can put as many as 20 of these amplifiers in parallel for a total output of 0.5 MW.

In addition to the 4-kHz full-power bandwidth, the 19-in.-wide, 24-in.-deep, and 5.25-in.-high unit has 20-kHz small-signal response and 350-µsec settling in current-source mode to 0.2% of final value. THD is 0.2% at 200 Hz with 85A-rms output. The $8900 amplifier can also act as a reference, because it offers high thermal stability of 1 mV/°C output offset drift in voltage mode and 4 mA/°C in current mode.
—by Bill Schweber

Copley Controls Corp, Westwood, MA. (617) 329-8200.