Woodward MRM4, Руководство пользователя

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Protective Elements
Thermal Model Module Counter Values
Value Description Default Size Menu path
I2T Used Thermal capacity used. 0% 0 - 1000% [Operation
/Measured values
/ThR]
I2T Remained Thermal capacity
remained. 0% 0 - 1000% [Operation
/Measured values
/ThR]
NumberOfTrips Number of trips since last
reset 0 0 - 65535 [Operation
/History
/TripCr]
NumberOfAlarms Number of alarms since
last reset. 0 0 - 65535 [Operation
/History
/AlarmCr]
UTC - Ultimate Trip Current
Functional Description
The Ultimate Trip Current (UTC) sets the current level at which a trip eventually occurs and is settable to a value
as a multiples of » Ib « (Full Load Amps (FLA)). This value represents the vertical line on the upper portion of the
non-RTD as shown in the protection trip curve labeled “Motor Protection Curve Example 2 (without RTD)”. The
ultimate trip current setting in this example is at 1 times the of » Ib « (FLA).
The user has to set the k-Factor which can be calculated by the following formula:
k
Factor
=
UTC
CT
PRI
=
Overload
factor
∗
I
b
CT
PRI
Please note that the settings for k-Factor and Ib have to be set within the Field Parameter menu.
For normal use, set » UTC « to the » k-Factor« times 100%. The » k-Factor « is found on the motor nameplate or
in the manufacturer’s data. Note that the relay does not trip at the moment the current goes above » UTC«
during motor running. Instead, it models the gradual stator heating for currents above » UTC « , and trips only
after some time has passed. The trip time depends on a variety of setting and operating factors, including the
motor nameplate data contained in other setting values.
Use a conservative value. In this case, a lower value of »UTC« than that dictated by the » k-Factor « if the motor
ambient temperatures may rise above 40ºC (104ºF) and the optional URTD Module is not used, otherwise stator
insulation damage or loss of motor life may occur. Also, consider lowering the » UTC « value if the motor is
suitably rated, yet additional safety is critical for the application.
If UTC is set above 100% times the service factor, motor damage could
result.
In systems where an RTD is used the » UTC « pick-up point is biased by the measured temperature. This is
shown in the example trip curve labeled “Motor Protection Curve Example 3” (with RTD) were you will see a shift
Page 392 EN MRM4 01/11