Trips and Fault Finding 7-3
590 Series DC Digital Converter
Trip Message and Meaning Possible Reason for Trip
THERMISTOR
The motor temperature is too high
Inadequate ventilation
Blower failure -check for direction, clogged air filters
(models above 70A bridge rating)
Excessive armature current - check nominal armature
current on nameplate against current calibration)
Note: The motor must be allowed to cool in
order to re-start the Converter.
Alarm time delay : 15 seconds
OVERVOLTS (VA)
Motor armature voltage has exceeded
120% of rated volts
Loose armature connection
Badly adjusted field voltage setting
Badly adjusted field current loop
Badly adjusted field-weakening bemf loop
Badly adjusted speed loop
Alarm time delay : 1.5 seconds
SPEED FEEDBACK
The difference between speed feedback
and armature voltage feedback is
greater than the SPDFBK ALM LEVEL
parameter value
If FLD WEAK ENABLE parameter is
enabled, speed feedback is less than
10% when in the field weakening region
Analog tacho feedback polarity incorrect (terminals
G3 and G4)
The ENCODER SIGN parameter’s polarity is incorrect
Disconnection of wiring, including fibre optics
Tachogenerator failure
Tachogenerator coupling failure
Alarm time delay : 0.4 seconds
ENCODER FAILED
No speed feedback signal
The SPEED FBK SELECT parameter is set to ENCODER
but an optional Encoder board is not fitted
Where applicable, check fibre optic cable for
damage, bend radius, operating length - refer to
Microtach handbook.
Check cable and connections on wire-ended encoder
FIELD FAIL
Field current is less than 6% of rated
current when in Current Control mode
Field current is less than 50mA when in
Voltage Control mode (with default
current burden of 15K)
Open circuit motor field - check connection and
measure field resistance
Faulty operation of field controller
Where an ac supply feeds the onboard field
regulator, check connections D1 and D2 for line-to-
line voltage (rather than line-to-neutral) - L1 into D1,
L2 into D2. Note that the 3-phase supply must be
present for mains synchronisation purposes.
For loads where no field supply is required, e.g. a
permanent magnet motor, set the FIELD ENABLE
parameter to disable to suspend this alarm.
Alarm time delay : 0.75 seconds
3-PHASE FAILED
3-phase supply failure
Total failure of supply, or missing phase of 3-phase
supply (detected under most circumstances) - check
supply to the controller, check high-speed thyristor
stack protection fuses, check power chassis coding
fuses.
Check the mains voltage of the Converter (refer to
Product Code). This alarm may not operate properly
with controller if the voltage is incorrect, i.e. wrong
unit or controller.
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