A maximum of six power supplies can be installed in the Enterprise Chassis. Either 25W or 21W power supplies are available. Two 25W power supplies are standard in model 8721-A1x. Additional power supplies are orderable per the following table. All installed power supplies must be the same.
Both power supplies are 8 PLUS Platinum-certified. The 25W modules are 25 Watts output rated at 2VAC to 28VAC (nominal), and 275W at 22VAC to 24VAC (nominal). The power supply has an oversubscription rating of up to 3538 Watts output at 2VAC. The power supply operating range is 2-24 VAC. The power supplies also contain two dual independently powered 4mm cooling fan modules that are powered not from the power supply itself, but from the chassis midplane. The fan modules are variable speed and controlled by the chassis fan logic.
The 21W power supplies are 21 Watts output power rated at 2-24VAC. Similar to the 25W unit, this power supply also supports oversubscription, the 21W unit can run up to 2895W for short duration. The 21W supplies have two independently powered dual 4mm cooling fans, that pick up power from the midplane included within the power supply assembly.
8 PLUS is a performance specification for power supplies used within servers and computers. To meet the 8 PLUS standard, the power supply must have an efficiency of 8% or greater, at 2%, 5%, and 1% of rated load with PF of .9 or greater. The standard has several grades, such as Bronze, Silver, Gold, and Platinum.
With 25W power supplies, the chassis allows configurations of power supplies to give N+N or N+1 redundancy. A fully configured chassis operates on only three 25W power-supply units (PSUs) with no redundancy, but N+1 or N+N is advised. Three power supplies (or six with N+N redundancy) allow for a balanced three-phase configuration.
All power supply modules are combined into a single power domain within the chassis, which distributes power to each of the compute nodes, I/O modules, and ancillary components through the Enterprise Chassis midplane. The midplane is a highly reliable design with no active components. Each power supply is designed to provide fault isolation and is hot swappable.
In the case of the 25W supplies, power monitoring of both the DC and AC signals allows the Chassis Management Module to accurately monitor the power supplies. Power monitoring with the 21W power supplies is planned to be made available at a later date.
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