DEC STD 122-1

This document, DEC Standard 122 Section 1 Revision A (EL-00122-01), dated March 17, 1983, outlines the mandatory methods and guidelines for measuring AC power parameters.

Purpose: To ensure uniformity and acceptable accuracy in testing AC power parameters across product engineering design and test groups for all new computer products marketed by Digital Equipment Corporation. This includes power supplies, power control equipment, rotating equipment (blowers, fans, motors), and distribution components (cables, filters, contactors, circuit breakers, connectors).

Key Measurement Areas Covered:

• AC Voltage and Current: Specifies the use of true RMS meters and defines accuracy and crest factor requirements, along with suggested instruments.
• Peak Value, Voltage, and Current: Describes methods for measuring peak amplitudes and suggests instruments.
• Crest Factor: Defines calculation from peak and RMS values.
• AC Power (Real and Apparent): Details single-phase and three-phase power measurement using wattmeters, including characteristics and suggested models.
• Total Power Factor: Explains its calculation.
• Measurement of Harmonics: Describes how to determine total harmonic distortion.
• Inrush and Start-up Currents: Provides detailed procedures, waveforms, and calculation methods for measuring transient currents during equipment startup.
• Phase Rotation: Explains how to determine the phase order in polyphase circuits.
• DC Current Component: Addresses the measurement of unwanted DC components in AC lines.
• Ride-Through Time: Describes the measurement of an equipment's ability to withstand voltage sags.
• Hold-Up Time: Outlines procedures for measuring the duration an output voltage remains within regulation after input power loss.

General Guidelines: Emphasizes using calibrated instruments traceable to the National Bureau of Standards, maintaining specified test conditions (e.g., temperature, source capacity, line impedance), avoiding average-sensing instruments, and meticulous recording of all test data.