FAST LINEAR TRIP MODE
The Fast Linear Trip Mode provides an adjustable linear trip that can be used for
very quick or very slow trips. The Model 777-FT family offers superior protection
for sensitive motors, quick trips in test panels, and fast trips to protect high torque
systems.
When the Fast Linear Trip Mode is activated (TC = J00), two new parameters, Motor
Acceleration time and Over Current Trip Delay are viewed and programmed in the
RD1 and RD2 positions. The RD1 and RD2 setpoints are still valid, but can only be
viewed and programmed by setting the trip class to any other class other than J00.
Note: Ensure Trip Class is set appropriately when changing RD1, RD2, MA,
or OCTD.
When the Fast Linear Trip Mode is used, the restart delays (RD1, RD2, and RD3)
will be reduced by approximately 50%. Example: RD1 setting = 010; RD1 time = 5
second
s.
PROGRAMMABLE PARAMETERS
NOTE: The unit can be programmed prior to installation by applying
120VAC to terminals ‘L1’ and ‘L2’.
The programmable parameters are the values the user must program to pro-
vide the correct protection for the application. All parameters are actual values
except the “VUB” and “CUB’ settings, which are percentages. The range these
parameters can be programmed to is found in the specifications at the end of the
manual.
LV/HV-
The recommended settings for
“LV”
(low voltage) and
“HV”
(high
voltage) depend on many factors such as motor usage, motor size,
environmental factors and tolerance of the motor. The motor
manufacturer should be consulted for “HV” and “LV” settings.
However, the NEMA MG1 standard recommends that “LV” and “HV” be
set to no more than 10% of the motor’s nameplate voltage. The setting
can be determined by multiplying the motor’s nameplate voltage by the
recommended percent over and under voltage (eg. The motor name
plate voltage is
575
V.
Set "LV" to 0.9 x 575 = 517 and "HV" to 1.1 x
575 = 632
.
NOTE:
“LV” can not be set higher than “HV”, so “HV” may have to be
adjusted
higher before the proper “LV” setting can be programmed.
VUB-
“VUB” is the voltage unbalance trip point. The NEMA MG1 standard
does not recommend operating a motor above a 1% voltage unbalance
without derating the motor. Voltage unbalance is determined from the
following formula:
THE FOLLOWING ARE GENERAL RECOMMENDATIONS. THE MOTOR
MANUFACTURUR SHOULD BE CONSULTED FOR EXACT SETTINGS.
-5-
07/25/03
