3-20
Malfunctions Not Indicated by a Fault
Measured field current is not
equal to parameter 118 “Fld
Cur Fdbk”.
If the field current measured by the
clamp-on ammeter is significantly
different (greater than 10%) from the
value reported in parameter 118 the field
feedback scaling is incorrect.
•
Initial calibration of the field control determines the field current
below Base Speed. The nameplate rating of both the motor
and drive determine the initial scaling calibration. Enter the
motor nameplate current rating in parameter 612 “Rated Fld
Mtr Cur”. Enter the field’s bridge rating as determined by the
field current jumper J1, not the drive nameplate rating, in
parameter 616 “Rated Fld Brdg I”. Refer to the Start-Up
chapter of the 1395 Installation Manual for values for
parameters 612 and 616.
If the initial calibration is correct, the Feedback Board may have
experienced a failure. This would be typified by the field being
phased full on and full current flowing in the motor field circuit.
However, no field current feedback would be registered at
parameter 118 “Fld Current Fdbk”. Replace the Feedback Board,
being sure that the burden resistors installed at TB2 and TB3 are
of the same value and type as installed in the original board.
The field current reference is
not equal to the motor
nameplate rating during velocity
regulation below base speed.
Parameter 117 “Fld Current Ref” is not
equal to parameter 612 “Rate Fld Motor
Cur”. For operation below base speed,
these two values should be equal.
•
Verify that parameter 676 “Field Flux Ref” is equal to 100%. If it
is less than 100% a reduced field current reference will be
commanded.
Also verify that parameter 115 “Flux Command” is equal to 100%,
when parameter 676 is equal to 100%. If it is not, the flux
reference select may be improperly programmed. For applications
where the velocity processor generates it’s own field current
reference, bit 2 of parameter 627 “Flux Mode Select” should be set
to 0. If bit 2 is set to 1, parameter 159 “Flux Feed Forward” will be
used as the field flux reference. Parameter 159 is used when an
external field flux reference is brought into the drive, typically
under master/follower configurations. Typically in a follower drive
(torque regulator) application, the field flux reference will be
brought into the follower, from the master drive (velocity regulator).
If the unit experiencing the malfunction is a stand alone or master
velocity regulator, it will generate a field current reference
internally.
The field current feedback is
not equal to the field current
reference indicating that proper
regulation cannot be obtained.
Parameter 117 “Fld Current Ref” is not
equal to parameter 118 “Fld Current
Fdbk”.
•
Verify the field voltage rating of the motor and the field voltage
rating of the drive under use is compatible. A drive with a 230V
AC input rating is capable of a field output of 150V DC, a 380V
AC of 250V DC, a 415V AC of 270V DC, and a 460V AC of
300V DC.
The measured motor voltage at
base speed, no load, is not
equal to the rated nameplate
motor armature voltage.
The armature voltage measured with a
DVM at A1 and A2 of the DC contactor,
at base speed with no load applied, is
not equal to the value entered at
parameter 610 “Rated Motor Volt”.
•
Fine tune the calibration of the constant field control to match
the flux requirements of the motor. The nameplate rating of
field current is a general estimate published by the motor
manufacturer, if more exact calibration is required perform the
following adjustments: Operate the motor at Base Speed
velocity, under no load, and place a DVM across the DC
contactor at A1 and A2. Verify that parameter 676 “Field Flux
Ref” is equal to 100%. Adjust parameter 612 “Rate Fld Mtr
Cur” in small increments until the voltage measured at A1 and
A2 is equal to the rated armature motor voltage as stated on
the motor nameplate. (Increasing parameter 612 will cause the
armature voltage to increase).
If parameter 612 must be increased to a value greater than
parameter 616, the next higher J1 setting on the feedback board
must be selected and the value of parameter 616 must be
changed to reflect the higher setting. Remove all power to the
drive before changing the J1 jumper selection. Verify that the
motor rated field is compatible with the drive rating in both voltage
and current.
Field Current Control Malfunctions
Malfunction
Symptom
Solution
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