Maintenance Bypass Mode
The UPS can be manually switched to Maintenance Bypass mode allowing the UPS to be electrically isolated from the critical load. The bypass source supplies the commercial AC power to the load through an internal circuit breaker.
CAUTION:
Critical load is not protected while the UPS is in Maintenance Bypass mode.
Figure 21 shows the path of electrical power through the UPS system when the UPS is operating in Maintenance Bypass mode.
BYPASS
RECTIFIER
| Bypass |
(BIB) | Input |
| |
(open) |
|
OUTPUT | (MBP) |
TRANSFORMER | |
| (closed) |
Rectifier Input
CB1
K4
K3 | Output | |
(MIS) | ||
| ||
(closed) | (open) | |
|
Input
Isolation
Transformer
DC/DC
CONVERTER
CB2
(closed)
BATTERY
Path of electrical power
Figure 21. Path of Current Through the UPS in Maintenance Bypass Mode
The
The major components of the Maintenance Bypass are described in the following paragraphs.
Maintenance Bypass (MBP) Circuit Breaker
This breaker is normally open. When closed, it feeds utility power to the critical load when the MIS breaker is opened.
Maintenance Isolation (MIS) Circuit Breaker
This circuit breaker is normally closed, feeding UPS power to the critical load. This breaker is opened to isolate the UPS after the MBP breaker is closed.
Maintenance Bypass (MBP) Circuit Breaker
This circuit breaker is normally closed feeding bypass power to the UPS internal bypass circuit. This breaker is opened to isolate the UPS bypass after the load is transferred to maintenance bypass.
The MBP and MIS breakers are electrically interlocked to limit the possibility of UPS system damage from improper operation.
44 | Powerware BPIII Harsh Environment UPS |
