VCB Flashcards
What is TOC?
Where is it located?
How many contacts?
When is the contact depressed?
Truck Operated Control
Located in the VCB cubicle floor to the right rear
One actuating lever
Will be depressed when the vcb is in the connected/ normal operating position regardless if the vcb is open or closed
When will the door lock solenoid be energized?
The door lock solenoid will be energized when the vcb is not in the connected/normal operating position and the vcb is not closed in test
What purpose does the door lock solenoid serve?
This solenoid prevents the key from being turned to the unlocked position which would allow the removal of the key to be placed in the cubicle door key which would allow you to unlock and open the door
Contact LSBB (charging motor)
Open only when charging spring is fully charged
PS2 BB
Clothes in the test connected and withdrawn positions open otherwise
PS1
Open in test connected and withdrawn positions closed otherwise
LSBB (below Y coil)
Closed until charging spring is fully charged open only when spring is fully charged
LS AA ( below SR. Coil)
Open until the charging spring is fully charged closed only when Fully Charged
How does the charging motor operate?
The charging motor will be energized when both LS BB and PS 2 are both closed. When the VCB is in the test or connected PS 2 BB is closed. When the VCB closes the charging spring discharges and closes LS bb. LS bb Will stay closed energizing the Charjean motor once the spring is fully charged LS bb opens de-energizing the motor
How do you close the VCB
1G1-CL is the control switch in the control room (closed in the closed position).
43g1 is the sync switch and is closed in the on position
41-1 is an aux. contact on field breaker and is closed when breaker is closed.
41p1 is a contact that is closed when the field breaker is in normal operating position.
5c1 opens when 5c1 is tripped
5p1 opens when 5p1 is tripped
DL is closed when the key is in the locked position
All these contacts closed SR coil will energize by the closed Y contact
Y coil energizes through LS bb (closes after spring is discharged) which closes 1 Y contacts to seal itself in and one opens to de-energize SR. Coil. The y coil is the anti pumping interlock.
52B closed when VCB is open and opens when VCB is closed.
LC contact is closed when operating mechanism is in reset position.
LS aa contact is closed when charging spring is fully charged.
What will cause the vcb to electrically trip?
Control switch at vcb Control switch on bench board 5c1trip 5p1 trip Field breaker opening Field breaker being removed from normal operating position SEL 751 arc flash relay
Can you verify the trip coil of the vcb?
Yes when the vcb is closed. No if the vcb is open because the red light on bench board and at vcb go through the trip coil circuit which indicates continuity when VCB is closed but not when open. However the pushing the red light on cubicle bypasses coil when in the open position.
What is Moc?
Where is it located?
How many contacts does it have?
When are the contacts depressed?
Motor Operated Control
The MOC is on the floor of the VCB cubicle, towards the front and just to the right of center
2 gang operated levers
The front is operated when the vcb is closed and is in the test position
The rear is operated when the vcb is closed in the connected/normal position
What causes SEL-751A to operate?
A flash of light measured in lumens and current flow in the gen cts
