A rack power distribution unit (PDU) is a device with multiple outlets designed to distribute power to networking equipment within a rack, including servers, storage devices and other equipment. For example, let’s say you have a 42U rack cabinet loaded with 42 1U servers, that’s 42 cords you have to find outlets for. PDUs solve this problem by taking the power supplied to the rack and distributing it via multiple outlets to the rack’s servers and networking equipment.

Basic and Smart PDUs

A basic PDU is a dependable, space-saving, cost-effective way to deliver power to wiring closets, server rooms and equipment racks from a UPS system, generator or utility wall outlet. It complements the benefits of a UPS system by adding more outlets than are provided by a UPS to essentially convert a single high-amperage UPS outlet to multiple low-amperage PDU outlets. A basic PDU is the easiest way to distribute facility UPS or generator power to multiple rack loads.

Intelligent or “smart” PDUs can be broken down into three categories:

Metered PDU
A metered PDU can locally monitor load level and avoid potential overloads with a built-in digital current meter while offering reliable, rack-mount, multi-outlet, single or three-phase, power distribution from any protected UPS, generator or mains input power source.

Monitored PDU
While similar to a metered PDU, a monitored PDU goes one step further with its ability to remotely monitor single- or three-phase voltage, frequency, and load levels in real-time via a built-in network connection. Output current consumption is displayed locally via a visual meter to warn of potential overloads before critical input sources become overloaded.

Connecting additional equipment to a PDU can overload it or the supply circuit, causing breakers to trip or equipment to fail. Both metered and monitored PDUs display load levels in real-time, allowing additional equipment to be connected safely. The primary input plugs into an On-Line UPS system. The secondary input plugs into a wall outlet. If the UPS system is taken offline for maintenance, repair or replacement, the PDU keeps the load powered by automatically switching from the primary input to the secondary input because of its ATS functionality. When the UPS system is restored, the PDU will switch back to the primary input.

Switched PDU
What if you want the ability to remotely monitor, connect or disconnect your data center loads? No problem! A switched PDU provides all of these capabilities. A switched PDU can locally monitor load level and avoid potential overloads with a built-in digital current meter, as well as remotely control individual outlets for the rebooting of locked equipment to avoid costly service calls, custom power-on/power-off sequences and load-shedding of non-essential loads during blackouts to extend battery backup runtime for critical equipment. Unused PDU outlets can be electronically locked off to prevent the connection of unauthorized hardware. Built-in local digital display and remote web/network interface reports detailed voltage, amperage and kilowatt output values per breaker bank / phase with additional reporting options for power unbalance percentage, IP address and optional sensor-based temperature and humidity data. The PDUs network interface connects to an Ethernet jack. Remote users can switch each of the PDUs outlets on or off via SNMP, Web or telnet.

As you can see, intelligent PDUs offer a multitude of advanced features that make it easier to reduce operating costs and increase uptime.