-
4 -
6/07 A1
PROGRAMMABLE PARAMETERS
The following settings MUST be programmed by the user in order to provide proper protection for
the application. All parameters are actual values except for the VUB and CUB settings; these are
programmed as percentages. The range each parameter can be programmed to is found on the
electrical specifications table on pages 15 and 16. See pages 9 and 10 for programming examples.
LV/HV
- The recommended settings for LV (low voltage) and HV (high voltage) according to the
NEMA MG1 standard are ±10% of the motors nameplate voltage. For other settings, the
motor manufacturer should be contacted.
Example:
The motor nameplate voltage is 230 volts. 90% and 110% of 230 is 0.9 x
230=207 volts for the LV setting and 230 x 1.1=253 volts for the HV setting. These
parameters are based on the average voltage going to the motor.
VUB
- VUB (voltage unbalance) is factory set to 6%. The NEMA MG1 standard says a motor
should not be operated above a 1% voltage unbalance without derating
the motor. Most
utility supplied power sources have a difficult time sustaining a 1% VUB. The motor
manufacturer should be consulted for an exact VUB setting. Setting VUB to 999 will disable
voltage unbalance protection but will not disable voltage SP protection.
V
oltage unbalance is calculated as follows:
%
Voltage Unbalance = [(Maximum deviation from the average)/Average] x 100%
Example:
Measured line-line voltages = 203, 210, and 212. The average =
(203+210+212)/3 = 208.3. The maximum deviation from the average is the greatest
difference between the average voltage (208.3) and any one voltage reading; 212-
208.3 = 3.7, 210-208.3 = 1.7 and 208.3-203 = 5.3. The maximum deviation from the
average is 5.3, thus voltage unbalance = 5.3/208.3 x 100= 2.5%.
MULT
- MULT (multiplier) setting is found on Table 1. The MULT setting is determined by the
current the unit will be monitoring. This allows the unit to display the correct current. Set
MULT first then set UC, OC and GF.
OC
-
OC (overcurrent) is typically set to the service factor amperage (SFA) of the motor or 100-
115% of motor full-load amps (FLA), which are determined by the motor manufacturer. If
any one leg exceeds the OC setting, the 777-P will follow the TC settings to determine
when to trip; in seconds or by following the trip class curve (see Figure 4).
UC
-
UC (undercurrent) is typically set to 80% of the full-load amperage (FLA) of the motor. This
is usually adequate for protection of loss of load for many pumps and motors, including
submersibles. If the motor is not pulling near full load amperage then the UC may have to
be set to something higher than 80% of FLA for adequate protection. UC can be set to 0 if
UC protection is not desired. The 777-P examines average current to determine if an
undercurrent trip condition exists.
CUB
- CUB (current unbalance) is factory set to 7%. SymCom recommends contacting the motor
manufacturer for a specific setting. Current unbalance is calculated the same way voltage
unbalance is calculated (see formula above). Current unbalance protection can be disabled
by programming CUB to 999. This will disable current unbalance protection and current
single phasing protection.
TC
-
The TC (trip class) setting determines how quickly the 777-P will trip when an overload
(overcurrent) condition is detected. TC is a dual-function setting—both a thermal trip class
(NEMA standard) and a linear trip delay (in seconds) can be set to establish when the 777-
