TM 9-6115-669-13&P1.14.5 InternalPowerSupply.PDU switching elements and lamps are designed for an internal operating voltage of +24 VDC. Theinternal operating voltage is delivered from the generators and/or generated by a power supply inthe PDU. Voltage from the generators is fed by buffer diodes V1, V2 (figure 1-12) directly into theinternal line power system. This feed operates during the activation phase when the generatorpower system is not yet supplying voltage. Once the generator has reached operating speed, voltageis present at PDU bus bars L1, L2, L3. This voltage is transformed by T13 and rectified by V5,making available an internal power supply of approximately +26 VDC during steady-stateoperation. The voltage then increases from approximately +24 VDC to approximately +26 VDC. Ifpower supply T13/V5 fails, diodes V1, V2 once again supply power operation is maintained.1.14.6IndicatorLampCircuits.The PDU contains a cabinet lighting system with lamp H12. Opening the access door closes switchS5, activating the interior cabinet lighting.Control panel lamps H1 to H11 are powered from a brightness control N7 (figure 1-12) in the formof a dimmer circuit. Lamp brightness is set with PANEL DIMMER potentiometer R1. LAMP TESTpushbutton switch S1 is used for lamp testing. The lamps contain two diodes which switch themeither for operation (e.g. relay contact 43/44 of K12 for lamp H10), or for lamp testing.1-30
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