-
8 -
1/05
PROGRAMMING EXAMPLES
Example #1
Motor to be protected: 3-phase, 460 Volt, 25 hp air compressor with a 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/TS-
Standard NEMA motor = 5, TS turned on.
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 = 20
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 a 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/TS-
Manufacturer suggests VUB = 5, TS turned on.
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 Figure 3, for this (and most) submersible pumps, TC = 10 (fast trip)
RD1-
To protect the pump from rapid cycling, RD1 = 60
RD2-
Since the motor is small and submerged in water, the motor will generally cool down
quickly. RD2=5
RD3-
The well history shows that it will fully recover in 2 hours. RD3 = 120
