| Tweet |
Custom Search
|
|
|
||
 TM 55-1905-219-14-11
5-117. SHIP'S COURSE INDICATOR - MAINTENANCE INSTRUCTIONS (Continued).
both the coarse and fine control transformers would again both equal zero (figure A). Thus the coarse
synchro system provides two null points in a complete cycle. Regarding the coarse control transformer
(1XCT), its null at the 180-degree point is an unstable null, because if the shaft were on either side of that
point, by an infinitesimal angle, the servo would drive toward the correct null, 180 degrees away. The fine
synchro has 72 null positions or 36 times as many as the coarse synchro system. If only the fine control
transformer (36XCT) were connected in the system, there would be 36 positions of the transmitter shaft that
would produce a stable null error voltage. Only one of these 36 positions is desired, that position being the
point where the 1XCT also provides a stable null.
3
The mixing network switches into the servo amplifier the fine error signal when the error is small (output of
the coarse synchro is small) and introduces to the amplifier the coarse error signal when the error is large
(output of the coarse synchro is large). The coarse error signal can be small enough at the 180-degree
point to result in the fine error signal being fed into the servo, through the action of the mixing network. If
only the 1X error voltage were applied at the 180 degree point, the servo would drive away from this false
null. But, because the 36X voltage has control, it drives the servo toward this 180 degree null point. The
36X error voltage negative between 175 degrees and 180 degrees tends to drive the servo to an increased
angle (180 degrees); where positive between 180 degrees and 185 degrees it tends to drive the servo to a
decrease angle 180 degrees - the same point. In other words, if this condition were tolerated the servo
would lock in at a false null.
FIGURE A
5-1307
|
||
|
||
