Welcome to G-TV! Today I will be showing you how to program the Symcom 777 motor protection
relay. I will use this demo case housing a 777-KW/HP to show the different settings and
simulate a motor for a 3 phase, 460 Volt, 5 horsepower magnetic drive pump with an FLA
of 7.1 Amps. I can program any of the features by rotating the mode select switch to the
desired position and holding the reset button while turning the dial on the right to change
the value of each setting. First, the "MULT" setting must be programmed to ensure a proper
display of current setpoints. "MULT" is the multiplication factor for determining
true current settings and represents the number of conductors passing through the main current
windows marked "A", "B" and "C," or current transformer ratio of external CTs. I will
set this according to the number of full load amps using the table here*. I will then go
to the LV setting to set my low voltage. Both the low voltage and high voltage settings
depend on the motor's specs. Generally, the NEMA MG1 standard recommends that "LV"
and "HV" be set to no more than plus or minus 10% of the motor's nameplate voltage. Since
my voltage is 460, I can set the "LV" to 0.9 times 460, which is 414. I will then go clockwise
to set the "HV". Still using 460 volts, I will multiply 1.10 by 460 to find my HV setting
of 506. Next is the VUB setting for the voltage unbalance trip point. This measures the voltage
unbalance from phase to phase. The trip point is determined by finding the maximum deviation
from the average line voltage across 3 phases and then dividing it with the overall 3 phase
line voltage average. NEMA MG1 recommends against operating a motor above a 5% voltage
unbalance under any circumstances. I will set the VUB to 5 to adhere to this recommendation.
Next, I will set the OC, which represents the maximum current drawn by the motor. It
is calculated by multiplying the full load current rating of the motor by the service
factor of the motor. Both values can be found on most motor nameplates. I will set this
to 8.2. My next setting is the LP for low power or UC for undercurrent. The LP setting
is adjustable on KW-HP models and is used to shut down the motor or pump on an underload
condition. Current drawn from a motor is non-linear relative on the load placed on a motor, monitoring
kilowatts often provides better resolution when setting trip points based on a loss of
load, since power consumption of a motor is linear. With my application, normal operation
is 2.86 KW and when the pump has a loss of flow in a dead head situation, it is 1.86
KW. I will set this to 2. This setting can also be displayed in horsepower instead of
kilowatts. The UC or undercurrent setting found in other 777 models is typically 80
percent of the FLA and can detect a loss of load for many pumps and motors such as a dry
well condition for submersible pumps based on the current draw of the motor. Next is
the CUB setting for current unbalance trip point. This setting can differ between motor
manufacturers. Most motor manufacturers will recommend operating with no more than a 5%
unbalance in current from phase to phase. I will keep this setting at 005. The next
setting, "TC" is the trip class for overload protection. The trip class defines the trip
delay when an overload is detected. TC is a dual-function setting with both a thermal
trip class and a linear trip delay can be set. While the standard trip classes are 5,
10, 15, 20, and 30, TC can be set from 2 to 60, with or without jam protection. Consulting
the Symcom manual will assist in picking which trip class is best for the application. I
will set this to 20 for general purpose motors. My next three settings are RD1, RD2, and RD3.
RD1 is the rapid cycle timer, RD2 is the restart delay after the overload relay trips and RD3
is the restart delay after an undercurrent. These settings will allow enough time for
the motor to start up or cool down as needed. �#RU" is the number of successive restart
attempts allowed after an undercurrent fault before the overload relay requires manual
reset. A setting of "0" is manual reset and a setting of "A" is continuously automatic
reset. For my application, undercurrent could be a serious problem if unchecked, so I will
change this to 0 to ensure a manual reset. My next setting is #RF, the number of successive
restart attempts allowed after a current unbalance, single phasing or overload fault. If the "oc"
prefix is selected the overload relay will automatically reset after an overload fault.
Since I do not want to have an automatic reset, I will select 1, giving the system one chance
to recover from an unbalance or single phasing problem before a manual reset is required.
The KW/HP version has PWS for the next setting, which is the power scale. This sets the range
for the LP setting. Other 777 models offer the UCTD setting for the undercurrent trip
delay timer. This is the maximum time the protection relay will tolerate an undercurrent
condition. The last setting to change is the GF for ground fault protection. This setting
detects a leakage current to ground and signals an insulation breakdown in the system. The
"GF" setting should be somewhere between 10% and 20% of the full load motor current. Ground
fault protection is a Class II ground fault protector and should not be used for personnel
safety, but can be used to indicate motor degradation for maintenance purposes. Once
my settings are programmed, I can move the dial to the run command and initiate my system.
The motor should be able to ramp up as indicated by the LED motor simulation here. For more
information on Symcom, check out our other videos on GTV. The Symcom 777, along with
thousands of other products and services are available at galco.com.