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6/07 A1
PROGRAMMING EXAMPLES
Example #1
Motor to be protected: 3-phase, 460 Volt, 25 hp air compressor with full load amperage rating of 34A
and maximum service factor amps of 37.4. Use the following calculations and reasoning to
determine the appropriate settings for this application.
LV-
460 x 0.90 = 414
HV-
460 x 1.10 = 506
VUB-
Standard NEMA motor = 5
MULT-
From Table 1 = 1
OC-
Service Factor Amperage = 37.4
UC-
FLA x 0.80 = 34A x 0.80 = 27.2
CUB-
Standard NEMA motor = 5
TC-
General purpose motor, TC = 20. No linear trip delay is desired, TC also = oFF.
RD1-
Since this compressor takes about 10 seconds to bleed off excess pressure after a
shutdown, setting RD1 = 20 will allow the compressor to unload before being restarted.
RD2-
Because the motor may be hot from running in an unbalance or single phase
condition, a motor cool-down time of 10 minutes, RD2 = 10, should be appropriate.
RD3/#RU- Because an undercurrent would signal a serious problem in this application (a broken
shaft or belt), #RU should be set to 0 for a manual reset. Therefore, RD3 does not
have any function
#RF-
Because an overload (overcurrent) fault signals a serious problem in this application
(e.g., worn bearings), "oc" should not be included in the #RF setting so that a manual
reset after an overload fault is required. A #RF=1 will give the system 1 chance to
recover from an unbalance or single phasing problem before manual reset is required.
UCTD-
Setting UCTD = 5 will allow normal operation and not allow the motor to run too long in
a failure mode.
GF-
A ground fault setting of 15% of full load amps will be a significant indicator that the
motor should be evaluated for repair or replacement. Therefore, GF = 34A x 0.15 =
5.1.
Example #2
Motor to be protected: 3-phase, 230 Volt, 5 hp submersible pump with full load amperage of 15.9A
and maximum service factor amps of 18.2. Use the following calculations and reasoning to
determine the appropriate settings for this application.
LV-
230 x 0.90 = 207
HV-
230 x 1.10 = 253
VUB-
Manufacturer suggests 5
MULT-
From Table 1, MULT = 2, 1 loop of main conductor
OC-
Service Factor Amperage = 18.2
UC-
FLA x 0.80 = 15.9 x 0.80 = 12.7
CUB-
Manufacturer suggests 5
TC-
From Table 3, for this (and most) submersible pumps, TC = 10. No linear trip delay is
required so TC also is set to oFF.
