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Trouble
Motor comes up to speed
too quickly or slowly
Motor starts hard, not softly
Controller is off but
motor is running
Motor overload relay
trips during starting
Motor not able to
accelerate load
Motor branch circuit
protection trips during
starting or running
28
Table 6 Troubleshooting - Continued
Cause
Improper settings
Load is too light
or too heavy.
Improper setup
Shorted SCR (LED 4
is on)
Unsuitable delta motor
Shorted SCR's
while running
Motor is overloaded
while running
Improper overload
relay heaters
Overload relay current
transformers incorrectly
wired.
Branch circuit protective
device incorrectly sized
Incorrect power wiring
causing a short on input or
load side of controller
Check/Remedy
Adjust Start Time T1 and Initial Voltage U settings per
paragraph 6.6.
Adjust load or consider decreasing or increasing motor size; for
proper controller selection, refer to section 3.
Refer to paragraph 6.6 for motor starting adjustments.
Check SCR's as described in paragraph 9.3.
A certain delta motor design (wired Inside Delta) will not start
softly with a high friction load (e.g., conveyor), only with a low
friction load (e.g., water pump). The soft start produces balanced
three-phase power to the motor, but it becomes stuck at a low
rpm until the end of the start ramp at high current. It then jumps
quickly to full speed due to the high voltage and current.
Check voltage from terminal A1 to A2 to verify that Run coil is
not energized. Check SCR's as described in paragraph 9.3.
Check for a mechanical cause of overload and clear.
Check that motor comes up to speed when started by applying
across-the-line full voltage directly to the motor. An alternative
is to use the controller with T1 set at 0 (0.5 seconds) and U at F
(80% full voltage).
a.
If motor can't accelerate the load, increase motor size; for
proper controller selection, refer to section 3.
b.
If motor accelerates the load, continue checking the follow-
ing causes.
Check heater table to determine correct heater size.
Verify current transformer wiring per applicable diagram(s).
Size the device in accordance with all applicable codes
(NEC/CEC).
Check circuit breaker trip settings.
Check all power wiring connections to determine if a phase-to-
phase or phase-to-ground short is present.
Siemens Energy & Automation, Inc.
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