Standard Specification for Insulation Resistance Monitor for Shipboard Electrical Motors and Generators

Abstract

This specification covers monitoring devices (monitors) for the automatic detection and signaling of low insulation resistance values in idle electrical motors or generators, or both. Monitors are intended for permanent installation in both existing or new panels and controller enclosures designed for marine application. These insulation resistance monitors shall be classified in four types: Type I are alternating current generator monitors, Type II are alternating current generator monitors, Type III are direct current motor monitors, and Type IV are direct current generator monitors. The enclosure materials used in the construction of the monitors are to be flame-retardant and the current carrying terminals shall be made of corrosion resistant material. The monitors shall isolate their measuring circuit from the line voltage, while the motor is operating, by the use of an integral isolating relay. In the design of these monitors, environmental factors shall be considered: operating temperature range, sealing, inclination, humidity, and vibration. Also, the monitor relays, voltage characteristics and operating accuracy shall be considered in the design of these monitors. Each monitor shall be subjected to the following: visual and mechanical examination and operational test.