S225-10-5
3-3
4. Motor holding switch closes, assuring that one tap change
will be completed.
5. Geneva pinion completes first revolution and continues to
rotate.
6. Geneva pinion drives the geneva gear through 60 degrees
and the scroll cam and roller plates transfer the front main
movable contacts from the neutral stationary contact N to
the stationary contact No. 1. Simultaneously, the reversing
movable contact is transferred from the reversing stationary
contact (VL) to the stationary contact (VR).
7. Neutral light switch opens.
8. Geneva pinion completes second revolution and continues
to rotate.
9. Geneva pinion drives the geneva gear, main drive shaft, and
scroll cam through 60 degrees and produces final wipe
action at the front main movable and reversing movable
contacts.
10. Motor holding switch opens.
11. Motor brake engages.
12. Motor stops.
A tap change from No. 1 raise position to neutral will be accom-
plished as described, except the geneva pinion will rotate clock-
wise. The reversing movable contact will be transferred from the
reversing stationary contact (VR) to the stationary contact (VL).
CONTENTS
All movable and stationary contacts employ copper-tungsten or
silver tips at points subjected to arcing duty. Contact points not
exposed to arcing employ a combination of ETP copper and sil-
ver to provide a high conductivity current path. Movable con-
tacts are split to make contact on both sides of mating parts and
resist separation during high current surges. Contact pressure is
maintained by steel leaf or compression springs. All contacts for
current tap changer models can be retrofit to older models.
OPERATING SEQUENCE - Spring-drive
When the spring-drive switch is in the neutral position and the
control calls for a tap change, the following events occur:
1. Motor brake releases and motor starts.
2. Motor holding switch closes, assuring that one tap change
will be completed.
3. The up slope of sprocket cam engages a lip of the spool. This
lifts the pin in the pin cam and frees it from the hole in the
actuator.
4. A projection on the sprocket cam contacts a leg on the pin
cam, and both turn.
5. Drive shaft, which is attached to the pin cam, begins to turn
the crank arm and the springs begin to extend.
6. Pin comes free from the lip on the spool and a spring pushes
it against the surface actuator.
7. Down slope of sprocket cam returns the spool to the start
position.
8. Pin drops into the hole in the actuator 180 degrees from the
start position.
9. At this point, the crank arm is at top dead center and the
springs are fully loaded. Drive shaft and crank arm, sprocket
cam, pin cam, and actuator are locked together and connect-
ed through the chain to the motor.
10. Motor drives all parts beyond top dead center.
11. Spring unloads, pulling pin cam and actuator through 18O
degrees at high speed. Pins on the actuator cause the con-
tact drive sprocket to index one tap position.
12. As the contact drive sprocket moves, it imparts motion to the
reversing switch segment and main movable contacts. This
action closes the reversing movable and reversing stationary
contacts and drives the main movable contact onto the adja-
cent main stationary contact. Also, the neutral light switch
opens.
13. Motor continues to turn the sprocket cam until the motor hold-
ing switch opens. The gear motor output shaft has completed
one revolution.
Should more than one tap change be required, the foregoing
sequence will be repeated {except reversing switch portion) until
the control is satisfied or the limit switch in the position indicator is
reached.
OPERATING SEQUENCE - Direct-drive
When the switch is in neutral and the control calls for a tap
change in the raise direction, the following events occur:
1. Motor brake releases and motor starts.
2. Geneva pinion rotates counter-clockwise to engage the gene-
va gear.
3. Geneva pinion drives the geneva gear, main drive shaft, and
scroll cam through 60 degrees and produces initial wipe
action atthe front main movable contact and reversing mov-
able contacts.
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