Specifications

4-10 888-2500-001 5/2/2013
WARNING: Disconnect primary power prior to servicing.
DAX-1/DAX-3
Section 4 Theory of Operation
4.4.2.2 SCR Firing Board Interface
The Power Supply Controller board interfaces with the SCR firing board and provides
the SCR enable / disable function and voltage references, which determine the
conduction angle of the rectifiers and thus the regulated DC bus voltage. A sample of
the B+ output is sent to the SCR firing board from the Power Supply Controller to close
the voltage regulation loop.
4.4.2.3 Power Supply Fault Status Reporting
The Power Supply Controller board reports AC phase loss, DC discharge fuse failure,
transformer over-temperature, and rectifier assembly over-temperature faults to the
Main Controller. Rectifier and transformer over-temperature faults, and AC phase loss
faults are reported to the Main Controller as a PS_FAULT, and DC discharge fuse
failure is reported to the Main Controller as PS_WARNING.
4.4.2.4 Samples to the Main Controller
DC current and AC voltage samples are provided for the DAX Main Controller.
4.4.2.4.1 DC Current Sample
A sample of the power supplies DC output current is taken across a current shunt
resistor, which is connected between the negative side of the rectifier assembly and
chassis ground. The voltage that is sensed across this resistor is fed into the input of an
op-amp and the output voltage scaling of the current sample is adjusted by adjusting the
gain of the op-amp. The current sample scaling is 0.09Vdc output / 1A DC input. This
current sample is sent to the Main Controller.
4.4.2.4.2 Transformer Secondary Voltage Sample
A sample of the transformers secondary voltage is provided so the Main Controller can
determine whether the AC mains is within +10/-15% of the nominal AC line voltage.
4.4.2.5 Over Current Protection
4.4.2.5.1 Rectifier and DC Output
The rectifier assembly and the DC output wiring and components of the B+ supply are
protected from over-current by properly sizing the transformer secondary fusing such
that DC over-currents will blow the secondary fusing before rectifier or DC output