Browse Prior Art Database

Phase Detector for Emergency Power Off Circuits

IP.com Disclosure Number: IPCOM000121939D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 77K

Publishing Venue

IBM

Related People

Abernathy, J: AUTHOR [+2]

Abstract

This device consist of two parts, phase detection and a power source that is not dependent on one phase of a three-phase electrical system. The phase loss monitor detects a loss of phase and removes power to the load.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Phase Detector for Emergency Power Off Circuits

      This device consist of two parts, phase detection and a
power source that is not dependent on one phase of a three-phase
electrical system.  The phase loss monitor detects a loss of phase
and removes power to the load.

      Illustrated in the figure is the circuit diagram for the phase-
loss monitor.  The phase-loss monitor requires single-phase
electrical supply to power the circuitry.  If a phase is lost and it
is the one that is powering it, the phase-loss monitor would not
operate.  Therefore, the following circuit was designed. Three
control relays (CRA, CRB, and CRC) are used to monitor power in each
of the phases.  If power is available in all three phases, all the
relays are energized and their normally open contacts in the circuit
will close.  Assuming that phase A is the preferred source, relay
CRA's other normally closed contacts following the CRB and CRC
contacts will open and interrupt the branches.  Assuming further that
phase B is the second preferred source, the normally closed contacts
of the CRB will open in the CRC branch.  Phase A is now the only
source for power.

      If phase A is lost, relay CRA is de-energized and its normally
open contact opens, isolating that branch.  The normally closed
contacts of CRA will close, and a complete circuit through the CRB
contact will be established.  The circuit through the CRC contact is
still interrupted by the normally closed contact of CRB.  The same
situation repeats regardless of which one or two phases are lost.

      The phase-loss monitor has a 0-10-second delay (provided by
...