GE VALUTROL MAIN CONTROL MODULE Instructions Manual page 22

To sImplIfy signal tracIng, the gain of the regulator and
drIve IS reduced and the speed feedback signal to the
regulator error amplifier is removed.
SIGNAL FLOW
The local reference LR IS applied directly to the input of the
linear tIme section, by·passing the
REF SCALE
adjustment.
The timed output TR wIll ramp to a voltage equal to LR in
magnitude and polarity in a time determIned by the setting
of
LIN TIME.
The local reference LR is also applIed to the input of the last
stage of the speed feedback section. The output SFB will be
equal to LR in magnitude, but opposite in polarity. The
tachometer scaling cirCUIt and its output TFB are
unaffected by the local reference and will remain at zero.
As the signal from SFB into regulator error amplifier IS
inhibited. The primary purpose of exercising SFB is to
check those specIal function circuits In the modification
rack whICh are programmed from SFB,and/ or SFB
functions of an MFC.
A dummy feedback signal to replace the normal SFB signal
is connected from the output of the regulator integrator
output DR to the input of the regulator error amplifier.
Under these conditions DR is equal to the magnitude ofTR
but opposIte in polarity as long as the current reference is
raIsed, the current feedback signal CFB will exceed the
current limit level set by
CUR LIM
and force the DR output
into negative saturation for forward current limIt and
positive saturation for reverse current limit.
Current feedback will also program the CEMF output to a
level proportional to the CFB level and the
COMP
adjustment.
The load Instrument output IMET WIll also respond to the
current reference.
The gain of the drive is reduced so that the phase control
reference PCR is equal to the magnitude of the driver
reference DR as long as the current reference IS set to zero.
With an oscilloscope, the initial pulse output IPU, and the
pulse output PO may be momtored to verify proper
operation. See FIg. 16 and 22.
DIAGNOSTIC RUN (SWITCH RIGHT)
In dIagnostIc run, the local reference LR and the diagnostic
switch are substituted for the reference{s) SR, JOGR and
the RUN and JOG switch inputs just as In dIagnostic static.
The drive then runs normally with one important
exception: system feedback is normal but the signal from
system feedback to the regulator error amplifier is inhibited
and the dummy feedback from DR is still in place.
22
The net effect IS the drive operates as a base speed voltage
regulator from the
LOC REF
potentIOmeter.
CALIBRATION PROCEDURE
The dIagnostIc card is used to generate the appropriate test
signals and operatIng modes to calibrate the drive.
If
a
dIagnostIc card has not been furnished, one may be ordered
or the test CIrcUIt shown in Figure 23 may be used.
Make all connectIOns prior to applying input power. To eXIt
from the DIAGNOSTIC RUN mode, push the RESET
button to inItIate a fault shutdown, then remove mput
power.
*
All connectIOns may be made to the test posts on the front
of the main control card except for CRM and FDR which
are located on the RTB terminal board.
+20V
CURRENT
REF'
-ZOV
LOCAL
REF'
DIAGNOSTIC STATIC
r----4CRM ..
+zov
>-----_---41---~ DPI
LOCAL
REF'
' O - - - - - 4 L R
-20V
)---..:....::=--~---~
MIIC
DIAGNOSTIC RUN
FIG. 23 DIAGNOSTIC TEST CIRCUITS
DPI
DP2
LR
F'DR.
eTa
To aVOId confusion and possible interactIOn, the
adjustments should be made
III
the following sequence.
Two sequences are listed, one when a motor field exciter
MFE is provided, and one when a
~otor
field control MFC
IS provided. Refer to the system elementary to determine
which has been furmshed.