Measurement Rack Power States

Table 8. Measurement Rack States of Operation
Power State PEP PDU UPS Temperature Controller
Off Off Off Off Off
Standby On (AC) Off Off On
EPO DC only Off On On
Remote EPO On (AC) Off On On
On On (AC) On On On
Table 9. Power State Descriptions
Power State Description Action
Off The system is entirely disabled with no power passing through the line filter or any internal test system components. To enter Off state:
  1. Switch the main breaker (CB outlet) on the power entry panel (PEP) to the OFF position.
  2. Disconnect MAINs power from the PEP.
To exit Off state, follow the process in Powering on the Measurement Rack.
Standby Power to the power distribution unit (PDU) and uninterruptible power supply (UPS) is shut off. Power is passing out of the PEP and into the thermostat emergency power off (EPO) panel. To enter Standby state:
  1. Move the main power switch on EPO panel to the Standby (1378) position.
  2. Safety shutoff thermostats on fan panel detect an unsafe air exit temperature.
To exit Standby state, move the main power switch to the ON (1378) position.
EPO Immediately cuts AC power from the PEP and PDU. The UPS remains powered so that the measurement instruments in the rack continue logging data. DC power passes out of the PEP and into the thermostat EPO panel.

Entering this state also triggers the remote EPO connector, which, when connected to an external safety loop, automatically shuts off external equipment.

 To enter EPO state, press the EPO button.

To exit EPO state, turn clockwise to release the EPO button.
Remote EPO Immediately cuts power from the PDU. The UPS remains powered so that the measurement instruments in the rack continue logging data. Power passes out of the PEP and into the thermostat EPO panel. The system enters Remote EPO state when other equipment connected to an external safety loop through the remote EPO connector enter an EPO state.

The system exits Remote EPO state after the external instrument exits its EPO state. The rack switches into its previous state.
On A change to this state begins the main power on sequence of the test system. The PDU receives AC power through the UPS from the PEP and enables outlets to other system equipment. The EPO panel is powered. To enter the On state, follow the process in Powering on the System.
Figure 11. Power Block Diagram

1378