Description of Optional MEMORY AND TIME DELAY P-C BOARD. Part Number

Transcription

1 TO Revised Description of Optional MEMORY AND TIME DELAY P-C BOARD Part Number HOBART BROTHERS COMPANY Airport Systems Group Troy, Ohio U.S.A.

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3 TO-210 Description of Optional MEMORY AND TIME DELAY P-C BOARD Part Number Description The information herein describes a a memory and time delay module, sometimes called a protective monitor module, which is an option available for the protective circuitry of various Hobart ground power units. This module is a printed circuit board identified as Hobart Part No This memory and time delay module employs the standard Hobart memory and time delay module, Hobart Part No C, along with one or more of a time delay circuit assembly identified by Hobart Part No This memory and time delay module is an integral part of the circuitry that protects the aircraft electrical system against damage which could result from overvoltage, undervoltage, overfrequency, or underfrequency. In a Hobart ground power unit, a voltage sensing module and a frequency sensing module are connected to generator output leads between the generator and load contactor. These solid-state modules sense any abnormal condition of voltage or frequency and signal the solid-state circuitry of the memory and time delay module to open the load contactor and disconnect output to the aircraft. The memory and time delay module has five memory circuits, one with a time delay for undervoltage. Each circuit is connected to a corresponding sensing circuit in the sensing modules. All memory circuits are connected to the module relay coil, and any one of the circuits can energize the coil to open the relay contacts. Thus, when a sensing device energizes any one of the module circuits, the module relay is also energized to break the load contactor holding circuit and allow the load contactor to open. A time delay system is designed into the undervoltage circuit to prevent nuisance opening of the contactor under conditions of momentary undervoltage in the generator output. An undervoltage condition which continues uninterrupted for a period of 4 to 6 seconds will cause the time delay circuit to open the load contactor. To prevent nuisance opening of the contactor under conditions of momentary overvoltage, overfrequency, or underfrequency in the generator output, memory/time-delay module (depending on the DASH NUMBER selected) permits various lengths of time delay for these abnormal conditions of voltage or frequency as explained in the following table. MODULE AND OVERVOLTAGE OVERFREQUENCY UNDERFREQUENCY DASH NUMBER TIME DELAY TIME DELAY TIME DELAY Second None None None Seconds None None None Seconds Second Seconds None Second None Seconds None Seconds Seconds Second Seconds Seconds Seconds None None December 10/90 Revised Page 1

4 TO-210 When a 400-Hz generator is purchased from Hobart Brothers, the memory/time-delay p-c board, Hobart Part Number , may be ordered as an option with any of the time delays or combinations of time delays described in the preceding table. 2. Protective Circuit Trip Values Trip values for protective circuits may differ slightly for various Series and Specifications of generator sets. However, typical trip values for protective circuits are as follows: Overvoltage trips at 130 V to 134 V Undervoltage trips at 102 V or below Overfrequency trips at 415 Hz to 425 Hz Underfrequency trips at 390 Hz to 395 Hz After a contractor trip, the module relay will remain energized (OPEN) and the indicator light on the control box panel or protective relay tray light will remain ON until the generator s reset switch is pushed to break the module 12-V DC circuit and allow the relay to return to normal, CLOSED position. 3. Customer Service If you have any questions concerning your Hobart Airport Systems Group equipment, you are invited to contact our service department by mail, telephone, or FAX. Write: Hobart Brothers Company Airport Systems Group Power Systems Division Service Department Troy, Ohio 45373, U.S.A. Telephone: (513) for Service Assistance (513) for Parts Assistance FAX: (513) Page 2 December 10/90 Revised

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