This manual describes the Elgar Model 751SL, 1001SL and 1751SL power sources. The series of power sources though functionally equivalent to previously available units, exhibit several notable improvements. Marked reductions in panel height, overall weight, and volume have been achieved. Also, provision has been made in each unit for incorporation of custom functions without resorting to special designs. Each power source described herein provides AC power at precise frequencies for testing, motor operation, and frequency conversion. The basic power amplifier consists of two DC supplies and a direct coupled amplifier driving a tapped output transformer. Nominal output voltage for each of the units is: 0-65, 0-130, 0-260 VAC. Output power at full and at less than full rated voltage is illustrated in the derating chart of Figure 1-1. Figure 1-2 illustrates a typical harmonic distortion curve. Each power source may be wired for 115, 208 or 230V input, 47-63 Hz single phase. 1.1.2 Output voltage and frequency are established by a plug-in oscillator. Output frequency range for these units is 45 Hz to 5kHz. 1.1.3 Equipment tests to meet military specification operating requirements over the frequency range of 47 to 63 Hz or 47 to 425 Hz are facilitated through the use of Elgar power sources. The basic power source output is single phase, however, multiphase power may be obtained by stacking two or three power sources, all driven by one multiphase plug-in oscillator. See Section III. 1.1.4 Each power source is contained in a standard rack mountable enclosure. A meter for output voltage monitoring, a power on indicator lamp, a voltage amplitude control and a power circuit breaker that applies line power to the unit are located on the front panel. Cooling air for the power amplifier is drawn through a side panel grills and exhausted at the rear of the enclosure. 1.1.5 The enclosure contains heatsink assemblies which comprise a two section power amplifier. Control circuitry is mounted on a plug-in circuit board with test points and an adjustment control for output voltage regulation. Output voltage monitoring is available at the rear panel terminal block and at front panel binding posts.