Emerson 7ADTB - Manual (Page 9)

TESTING & SERVICE
(continued)
2--3
handle
shaft extension
frame
UP opens the
Emergency source
contacts
DOWN closes the
Emergency source
contacts
UPPER SHAFT
Figure 2–2. Maintenance handle operation for Emergency source contacts (upper shaft).
handle
shaft externsion
frame
UP closes the
Normal source
contacts
DOWN opens the
Normal source
contacts
LOWER SHAFT
Figure 2–3. Maintenance handle operation for Normal source contacts (lower shaft).
Table C. Maintenance handle positions. ALL POWER MUST BE OFF !
Transfer Switch Position Interlocked Shafts Maintenance Handle Shaft Indicators
Normal
E
t t h ft
shaft
extension
up
E = O
upper contacts open
Normal
N
link
contact shafts
shaft
extension
up
N = C
lower contacts closed
Load
E
up
E = O
upper contacts open
Load
Disconnected
N
down
N = O
lower contacts open
Emergency
E
down
E = C
upper contacts closed
Emergency
N
down
N = O
lower contacts open
* Link between contact shafts prevents closing both N and E contacts. The shaft extension and contact shaft turn in opposite
directions through a cam–follower mechanism. If Normal and Emergency connectios are reversed this operation is also reversed.