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3.2. Connecting Power to DC-Powered MWS1000

Warning

Before performing DC power procedures, ensure that power is removed from the DC circuit. To ensure that all power is off, locate the circuit breaker that services the DC circuit, switch the circuit breaker to the off position, and secure the switch handle of the circuit breaker in the off position.

Important

Do not mix AC and DC power supplies within the same appliance. Damage to the appliance might occur.
Ensure that the equipment rack is properly grounded and the appliance has a good low-resistance ground bond to the rack before you connect power to the DC power supplies.
Connect DC power to the appliance by attaching power cables from the external DC power sources to the terminals on the power supply faceplates. You must provide the power cables.
To connect the DC source power cables to a DC power supply on the appliance:
  1. Switch off the dedicated customer site circuit breaker for the power supply. Ensure that the voltage across the DC power source cable leads is 0 V and that there is no chance that the cable leads might become active during installation.
  2. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to an ESD point on the grounded rack.
  3. Verify that the DC power cables are correctly labeled before making connections to the power supply. In a typical power distribution scheme where the return is connected to chassis ground at the battery plant, you can use a multi-meter to verify the resistance of the V- (–48V) and V+ (RTN) DC cables to chassis ground:
    • The cable with very large resistance (indicating an open circuit) to chassis ground is V- (–48V).
    • The cable with very low resistance (indicating a closed circuit) to chassis ground is V+ (RTN).

    Important

    Ensure that power connections maintain the proper polarity. The power source cables may be labeled (+) and (-) to indicate their polarity. There is no standard color coding for DC power cables. The color coding used by the external DC power source at your site determines the color coding for the leads on the power cables that attach to the terminals on each power supply.
  4. Attach the power cables.
    • Remove the protective cover from the DC terminals on the power supply.
    • Loosen the DC terminal screws.
    • Insert the positive (+) DC source power cable and tighten the screw to secure the cable to the V+ (RTN) return terminal.
    • Insert the negative (-) DC source power cable and tighten the screw to secure the cable to the V- (–48V) input terminal.
    • Replace the protective cover over the DC terminals on the power supply.
  5. Attach the grounding cable.
    • Remove the screw from the grounding terminal on the power supply.
    • Insert the screw through the grounding lug on the cable and tighten the screw to secure the cable to the power supply grounding terminal.
  6. Route the power and grounding cables so that they do not protrude or prevent access to components of any equipment in the rack. Secure the power and grounding cables with plastic cable ties, which you must provide.
  7. Verify that the power and grounding cables are connected correctly, that they are not touching or blocking access to device components, and that they do not drape where people could trip on them.
  8. Switch on the dedicated customer site circuit breaker for the power supply.