Force Output Relay; S5 Thermal Model; Motor Thermal Limits - GE 469 Instruction Manual

S5 Thermal Model

Force Output Relay

FORCE
OUTPUT RELAYS
NOTE

Motor Thermal Limits

GE Multilin
PATH: SETPOINTS S4 OUTPUT RELAYS
[ ] FORCE 1 TRIP
RELAY: Disabled
FORCE TRIP RELAY
MESSAGE
DURATION: Static
FORCE 2 AUXILIARY
MESSAGE
RELAY: Disabled
FORCE 2 AUX RELAY
MESSAGE
DURATION: Static
FORCE 3 AUXILIARY
MESSAGE
RELAY: Disabled
FORCE 3 AUX RELAY
MESSAGE
DURATION: Static
FORCE 4 ALARM
MESSAGE
RELAY: Disabled
FORCE ALARM RELAY
MESSAGE
DURATION: Static
FORCE 5 BLOCK START
MESSAGE
RELAY: Disabled
FORCE BLOCK RELAY
MESSAGE
DURATION: Static
The output relays can be independently forced in static or dynamic mode. In static
mode the selected relay will operate as long as it is in the "Enabled" state. Only
when the user enters "Disabled" will the selected relay reset. In dynamic mode the
user specifies the operate time (1 to 300 seconds) and the selected relay will
operate for the specified duration.
The option is NOT allowed when the selected relay output is
FORCE OUTPUT RELAY
already active due to trip or alarm condition, when the 469 is in start block
condition, or when the 469 is not in service.
IMPORTANT NOTE: The forced relay will override any trip or alarm conditions. (i.e.
when the relay is forced and trip occurs, the relay will still be enabled when the trip
condition is reset).
Control power loss in the 469 will reset all forced relays.
S5 Thermal Model
One of the principle enemies of motor life is heat. When a motor is specified, the
purchaser communicates to the manufacturer what the loading conditions and duty
cycle will be, as well as, environment and other pertinent information about the
driven load such as starting torque, etc. The manufacturer then provides a stock
motor or builds a motor that should have a reasonable life under those conditions.
Motor thermal limits are dictated by the design of both the stator and the rotor.
Motors have three modes of operation: locked rotor or stall (when the rotor is not
turning), acceleration (when the rotor is coming up to speed), and running (when
the rotor turns at near synchronous speed). Heating occurs in the motor during
each of these conditions in very distinct ways. Typically, during motor starting,
locked rotor and acceleration conditions, the motor is rotor limited. That is to say
that the rotor will approach its thermal limit before the stator. Under locked rotor
conditions, voltage is induced in the rotor at line frequency, 50 or 60 Hz. This
voltage causes a current to flow in the rotor, also at line frequency, and the heat
2
generated (I R) is a function of the effective rotor resistance. At 50 or 60 Hz, the
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Motor Management Relay
FORCE OUTPUT RELAYS
Range: Disabled, Enabled
Range: Static, 1 to 300 s in steps of 1
Range: Disabled, Enabled
Range: Static, 1 to 300 s in steps of 1
Range: Disabled, Enabled
Range: Static, 1 to 300 s in steps of 1
Range: Disabled, Enabled
Range: Static, 1 to 300 s in steps of 1
Range: Disabled, Enabled
Range: Static, 1 to 300 s in steps of 1
469
5–29