- On-line Modes
- Bypass Modes
- Automatic Voltage Regulation Mode
The UPS continually monitors internal systems and the incoming utility power. The UPS will automatically change between the modes, as required. The change is accomplished with no intervention by an operator. The detection logic and the switching logic inside the UPS ensures that the changes in the operating mode are automatic and transparent to the critical load.
A computer connected with an RS-232 cable allows system monitoring with optional UPS monitoring software. The cable is connected to the RS-232 port located in the system cabinet of an MMS system.
| |
| Illustration 1 | g02849139 |
|
System online mode power flow | |
When operating in the Online mode, the system is ready to protect the load.
When the system is in the "Online Mode", the input and output contactors are closed and the bypass breaker is open. Power flow through the system is via the input contactor, the line static switch, the line inductor, and the output inductor. The utility inverter is on.
Online mode is the standard operating mode for the system. When the system is in this mode, the load is protected. The system has the capability of discharging to support the load.
The system enters this state when the flywheel reaches 4000 RPM and there is enough stored energy in the flywheels to support the load. The flywheels have not yet reached standby speed. The system can sustain discharge in this state.
When the system flywheel reaches the nominal speed of 7700 RPM, the system is in the Online (standby) state. The UPS is regulating voltage and ready to discharge the flywheels to protect the load. 7700 rpm is the rated idle speed for the flywheel.
| |
| Illustration 2 | g02849150 |
|
Online discharging mode | |
The system enters the online discharging state when the unit is supplying power to the load. If power is disrupted, the system changes to this state.
| |
| Illustration 3 | g02849186 |
|
System bypass mode power flow automatic voltage regulation (AVR) mode | |
Repeated errors that cause the system to move between the bypass mode and online mode can lock the system into the bypass mode. When the system is locked in the bypass mode, the user must change the mode of the system via the keyswitch or UPSView.
Bypass Mode - Bypass Mode directly connects the incoming utility power to the critical load while bypassing the UPS system. The load is not protected when the UPS is in "Bypass Mode". The load can be affected by a disruption of the incoming power.
The bypass circuit also provides a path for power directly from an alternate AC source.
The system enters "Bypass Mode" at through one of the following events:
- Start-up
- The keyswitch (manual)
- Fault recovery failure
Bypassed-Verify Signals - When in the bypassed-verify signals state, the system verifies that the correct telemetry is present. The bypassed-verify signals state is used during system starting and during error recovery.
Bypassed-Auto Start - The bypassed-auto start is the default state at start-up. The UPS cannot immediately protect the load after the system is started. During the normal operation, the UPS will enter automatic voltage regulation (AVR) mode.
AVR (Automatic Voltage Regulation) Mode
AVR mode can be entered for one of the following reasons:
- Start-up
- Flywheel error
- Automatic Voltage Regulation Auto Start
The system remains in the AVR mode until the system is charged and sustain discharge. During the AVR auto start state, the flywheel must achieve a rate of 45 RPM before changing to the AVR charging state.
- Automatic Voltage Regulation Charging
The system enters this state when the UPS starts to charge the flywheel. When the flywheel has achieved nominal speed, the system enters the online stand-by state. Normally, the system enters the online charging state when the flywheel reaches 4000 RPM.
- Automatic Voltage Regulation Verify Signals
When the UPS is in the verify signals state, the UPS verifies that the correct system telemetry is present.