881 Power Controller User Guide

This document is the 881 Power Controller User Guide (EK-881PC-UG-003), prepared by Educational Services of Digital Equipment Corporation in April 1988.

The guide provides installation and operation information for the 881 Power Controller, a general-purpose, three-phase device designed to control and distribute AC power to various components (like power supplies and fans) within an operating system.

Key aspects of the 881 Power Controller highlighted include:

• Functions: Controls large amounts of AC power with low-level signals, distributes power to single-phase loads on a three-phase system, protects data equipment from electrical noise, and disconnects power for servicing or in case of overload.
• Features: Supports local and remote switching, offers only switched receptacles, uses convection cooling, is rack-mountable, includes AC-line filtering, a moveable strain-relief elbow, and a DIGITAL power control bus with a delayed output for sequencing other controllers.
• Versions: It comes in two versions, 881A and 881B, which differ primarily in input/output voltage and current ratings:
  • 881A: 120/208 Vac nominal input, 120 Vac output, 24A per phase continuous rating, 15A max per outlet, uses NEMA L21-30R plug.
  • 881B: 220-240/381-416 Vac nominal input, 220-240 Vac output, 16A per phase continuous rating, 10A max per outlet, uses IEC 309-type plug.
  • Both versions have 9 switched output receptacles and are 19-inch rack-mountable.

The document is organized into three main chapters:

1. General Information: Introduces the controller, its functions, features, and specifications.
2. Installation: Provides detailed instructions for rack-mounting the controller, connecting AC loads (emphasizing load balancing across phases and adherence to current ratings), and setting up the Digital Power Control Bus (with options for delayed output) and External Sense connections. Warnings regarding hazardous voltages and proper plug orientation are included.
3. Operating Instructions: Explains the use of controls like the circuit breaker, the BUS/OFF/ON switch (for local, remote, or off control), and the Power Control Buses. It also describes the External Sense connector for sensor-triggered power removal and offers a troubleshooting checklist for common issues.

The guide notes that while the Digital power control bus allows for normal control of power states, it is not intended to meet emergency power control requirements as specified by NFPA. It also states that schematics are provided for qualified service personnel only.