9-4
Diagnostics
Fault Definitions
(cont.)
Voltage Unbalance
①
Voltage unbalance is detected by monitoring the three phase supply
voltages. The formula used to calculate the percentage voltage
unbalance is as follows:
V
u
= 100 (V
d
/ V
a
)
V
u
: Percent voltage unbalance
V
d
: Maximum voltage deviation from the average voltage
V
a
: Average voltage
The controller will shut down when the calculated voltage unbalance
reaches the user-programmed trip percentages.
Stall Protection
Stall protection is enabled at the end of the programmed ramp time
after a motor has been started. If the controller senses that the motor
is not up-to-speed at the end of ramp, it will shut down after the user-
selected delay time has elapsed.
Jam Detection
②
Jam detection operates when the SMC Dialog Plus controller status is
“at speed.” The controller will shut down when the motor current
reaches the user-defined trip level, which is based on a percentage of
the programmed motor full load current rating.
Overload Protection
Overload protection is enabled in the Calibration group by
programming the:
• Overload class
• Overload reset
• Motor FLC
• Service factor
Refer to Chapter 5 for more information on calibration.
Underload
②
Underload protection is available for undercurrent monitoring. The
controller will shut down when the motor current drops below the trip
level. This trip level, a percentage of the motor’s full load current
rating, can be programmed.
①
Voltage unbalance protection is disabled during braking operation.
②
Jam detection and underload protection are disabled during slow speed and braking operation.
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