Main reversing movable contacts
The reversing switch changes the polarity of the tapped
winding. When the QD5 Quik-Drive tap-changer is in neutral
position, the reversing switch is located on the âVNâ
Reversing Neutral Stationary Contact. In the open position
the reversing switch is not in the load current circuit.
The reversing switch motion on the QD5 tap-changer occurs
as the main movable contacts enter or leave the neutral
position. The QD5 tap-changer reversing switch movable
contacts interact with the three reversing stationary
contacts during the buck and boost operation of the tap
changer.
The first tap step in either direction rotates the Reversing
Segment actuator causing the Reversing Segment Actuator
arms to rotate the reversing switch and engage the
appropriate reversing stationary contact. When the tap-
changer receives a signal for raise and the reversing switch
contact is in neutral, the reversing movable contacts will
move clockwise on to the VR stationary bridging the VR and
VN stationary contacts. In the lower direction from neutral
the reversing movable will move counter clockwise on to
the VL stationary contact. The reversing movable will be
bridging the VL and VN when moving in the lower direction.
Micro switches
Micro switches are use for the holding switch, reversing
logic, neutral indication and taping limit logic switches.
Two sets of normally closed switches are use to provide a
safety switch circuit to prevent the tap-changer from tapping
beyond 16R and 16L acting as a fail-safe to the mechanical
stop. The switches enable the tap changer to step back from
the mechanical stop when the holding switch is closed.
The micro switches used are rated for â40°C to 130°C,
5 Amp 125/250 Vac rating. The switches are designed to
exceed one million operations at QD5 tap-changer current.
QD5 tap-changer operating sequence
When the tap-changer is in the neutral position and the
control calls for a tap change, the following events occur:
1. Motor will start and drive the chain sprocket.
2. Rotation of the chain sprocket rotates the drive pinion.
3. The drive pinion cam engages and closes in the holding
switch.
4. Drive pinion roller engages the position indicator drive
gear advancing the position indicator pointer.
5. The sprocket drive roller engages the Geneva gear
rotating the Geneva gear.
6. As the sprocket rotates and the holding switch is
actuated, the sprocket cam dis-engages and releases
the brake.
7. The rotation of the Geneva gear causes the reversing
segment actuator to operate which moves the
reversing switch movable contacts, via the linkage tying
the reversing segment actuator to the reversing switch
from neutral to VR or VL.
8. Rotation of the Geneva gear relocates the movable
contacts on the stationary contacts.
9. Drive pinion cam returns to the open area opening the
holding switch.
10. Tap Change is completed.
Figure 9. Reversing movable contact assembly.
4
QD5 QUIK-DRIVE TAP-CHANGER INSTALLATION AND MAINTENANCE INSTRUCTIONS MN225012EN March 2016
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