Elgar SW5250A Service Manual download pdf (Page 17)

SERVICE MANUAL THEORY OF OPERATION

1-7

The sinewave references are fed either directly to the servo amplifiers or are AC

coupled, depending on the selected coupling mode of operation. The servo amplifiers

operate on the sinewave reference and the local or remote sense lines. The output of

the servo amplifiers feed the power amplifier drivers. Phases B and C have a mux that

selects between the output of their respective servo amplifiers or phase A’s servo

amplifier. This allows the power supply to operate in multiphase or single–phase mode.

Each power amplifiers current is sampled and processed through a summing bus that

allows multiple TW chassis to be paralleled. This summing bus output is then filtered

and fed into the front end of the eight–channel analog to digital converter. The ADC

also samples sense voltage, redundant over–voltage, and external user input.

The DSP reads one of the eight analog inputs to the ADC once every 12.5

microseconds. The sampled values of voltage and current are processed into RMS

current, RMS voltage, peak current, and instantaneous power. These values are

passed to the Digital Control Board for further calibration scaling and presentation to

the user.

1.6 HOUSEKEEPING BOARD (HSKP)

The HSKP board receives 48Vdc input from the power module(s) via the backplane

board where the 48V inputs are paralleled and delivered via J7A connector to the HSKP

board. The 48V is then delivered to the housekeeping circuit and also via the J3

connector to power the fans of the fan panel assembly. The housekeeping power

supply circuit consists of a push-pull converter producing two non-isolated and five

isolated outputs. These seven output voltages supply power throughout the TW

chassis. The voltages developed by the housekeeping supply are as follows:

• +/- B (+/-13V) supplies (chassis potential): Used to power circuitry at chassis

ground potential throughout the front panel boards.

• +/-15V analog supplies: Used to power circuitry at analog ground potential

throughout the amplifiers and front panel boards.

• +5V & -24V supplies (chassis potential): Used to power circuitry at chassis

ground potential throughout the front panel boards.

• +5V digital supply: Used to power circuitry at digital ground potential throughout

the amplifiers and front panel boards.

Note that the HSKP board does not supply voltages to the PFC, rectifier, or DC/DC

assemblies. For an explanation on how the bus voltages for these assemblies are

supplied, consult the theory of operation for each individual assembly.

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Elgar SW5250A Service Manual Page 17