Understanding UPS Operation
3.2 Bypass Mode
The UPS automatically switches to Bypass mode if it detects an overload, load fault, or internal failure. The bypass source supplies the commercial AC power to the load directly.
C A U T I O N
The critical load is not protected while the UPS is in Bypass mode.
Figure 3-2 shows the path of electrical power through the UPS system when the UPS is operating in Bypass mode.
Bypass Input
Rectifier Input
Rectifier
CB1
Bypass |
K4 |
Inverter
K3
Output
(Open)
Transformer
Path of electrical power
Battery
Figure 3-2. Path of Current Through the UPS in Bypass Mode
You can transfer the UPS from Normal mode to Bypass mode manually. However, the UPS switches automatically to Bypass mode whenever the inverter can no longer supply the critical load. If the UPS transfers to Bypass mode from Normal mode due to any reason other than operator intervention, the UPS automatically attempts to transfer back to Normal mode (up to three times within a 10-minute period). The fourth transfer will lock the critical load on the bypass source and requires operator intervention to transfer.
Bypass mode is a normal operating mode, and not an alarm condition. However, if the UPS is unable to return to Normal mode following an automatic transfer to Bypass mode, an alarm condition is recorded.
EATON Powerware® 9315 UPS | 3−3 |
