Rockwell Automation 1502 Medium Voltage Contactor, 800A (Series D and E) - Manual (Page 47)

4-18 Maintenance
1502-UM051E-EN-P – June 2013
Altitude Adjustment
Vacuum contactors are sensitive to the altitude at the installation site. This is due
to the fact that the atmospheric pressure assists in closing the main contacts by
exerting force on the bellows at the movable end of the vacuum bottles. Since
this force is proportional to the difference between internal bottle pressure and
external atmospheric pressure, the return spring must be adjusted for the ap-
propriate altitudes. Contactors are factory set for the altitude at which they are
originally installed. If a contactor is relocated to a different altitude range (see
Table 4.A), a spring adjustment is necessary for proper operation.
The following procedure shall be used to make the correct settings.
1. Determine what altitude range the contactor is set up for by checking the
rating label (also refer to the Catalog Number Explanation).
2. Measure and record dimension “A” as shown per Figure 4.24.
Note: Dimension “A” will vary from contactor to contactor, there is no
predetermined value.
Compression Bolt
Locking Nut
Return Spring
AA
Figure 4.24 – Return Spring Assembly
3. Loosen the compression bolt locking nut and adjust the position of the
compression bolt according to Table 4.A. Dimension “A” is changed by the
amount shown on the table. For example, if the contactor’s existing range
is 0-1000 m and the desired range is 3000-4000 m, increase dimension “A”
by 4.93 mm (0.194 in.). If the contactor’s existing range is 4000-5000 m
and the desired range is 2000-3000 m, decrease dimension “A” by 2.69 mm
(0.106 in.). After dimension “A” has been set for the desired altitude range,
re-tighten the locking nut.