Highly Robust Electronic Power Switch (EPS) Module Reduces the Threat of Downtime

by Rob, Lead Engineer 3. June 2011 13:32

API's focus in creating the new EPS module for 7832 series DC PDU

Today’s network managers primary objective is to manage power utilization in the most efficient and effective means possible, and one way to achieve these objectives is to implement equipment that provides remote control and monitoring over a network. By monitoring the status of outlets, network managers get a picture of their operation and its moment by moment condition. Employing SPMS DC PDU’s with EPS modules, Network Mangers now have the capability to remotely observe the status of each outlet, as well as, remotely control individual outlets based on demand and priority.

The 7832 DC PDU capabilities work in concert to support the network manager’s utmost objective of maintaining data availability and quality of service in data centers or any other type of Power Distribution application where reliable DC power application is required. Basically, the Electronic Power Switch is an electronic circuit protection device. Being electronic, it has certain advantages over and above a mechanical circuit breaker and fuses. As an electronic device the EPS has no moving parts to wear out – an EPS can be remotely controlled to switch on and off for over a million cycles without wearing out components. Since the EPS has no internal mechanism or contacts it is not subject to arcing or contact corrosion or oxidation, and thereby, eliminates the requirement for periodic or preventive maintenance. And the EPS provides a status indication of its output state which is used by the controller to verify command state or a notification of a tripped condition.

The EPS incorporates MOSFET devices as the power switch which provide the advantages as noted above, however, if overstressed they will fail and they’re failure mode is a short. To mitigate this undesirable failure mode several measures have been taken in the new EPS card. Firstly the EPS module has enhancements to maintain the MOSFET within its safe operating area to minimize stress on the MOSFET particularly when turning on into a high bulk capacitive load. Secondly the new device has a very fast reaction time to short circuit conditions. The card’s instant trip mechanism will respond to an over current above 200% of rated current within 1msec again minimizing the stress on the MOSFET as well as protecting the load. Thirdly the EPS card incorporates Transient Voltage Suppressors to protect the MOSFET from over voltage surges. Just as a circuit breaker or fuse the EPS incorporates a trip delay (see chart) within the 120% to 200% of rated current to allow for typical transients and surges during normal operation. Once the EPS detects an over current and the condition continues beyond the delay period the EPS will declare a fault or trip condition by turning off the MOSFET and setting a status flag to indicate a fault condition as been acted on. To recover from a fault or trip condition the EPS must be commanded off. (This is handled in the 7832 PDU by way of the Retry command.)

How to apply the EPS in your application. (Reference configuration chart.)

Size the EPS to your known load. If you know the load characteristics chose the module from the chart noting the Max Bulk Capacitance. If you are not sure of the bulk capacitance rating for a given load chose a module with the desired current rating and test in your application. If the EPS trips when attempting to turn on into the load try an EPS with the next higher current rating. (Insure the wiring and equipment can accommodate the higher current rating.) If this second attempt was not successful then contact technical support for further assistance.

Download the Reference Configuration Chart Now! EPS_Module_Configurations.pdf (19.68 kb)

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