The UPS 1200 continually monitors internal components and incoming utility power. The UPS 1200 changes modes automatically, as required. These changes are made without the intervention of an operator. Detecting and switching the logic inside the UPS 1200 ensures that operating mode changes are automatic and transparent to the critical load.
A computer that is connected with an RS-232 cable allows monitoring of the system with the optional UPS View Software. The cable is connected to the RS-232 port that is located in the Customer Interface Tray. The Customer Interface Tray is located on top of the Controls Cabinet.
Refer to the following list for the main operating modes of the UPS 1200:
- On-line Mode
- Bypass Mode (UPS/SMS only)
- Off-line Mode (Paralleled MMU only)
- Automatic Voltage Regulation Mode
- Shutdown Mode
The operator can command the system to enter the On-line Mode or the Bypass Mode via the Graphical User Interface. When an operator presses the "EPO" button that is located on the front of the Controls Cabinet, the system enters the Shutdown Mode. The operator cannot directly place the system into the Automatic Voltage Regulation Mode. Automatic Voltage Regulation Mode is an operating mode that the system enters only under certain conditions. If the system is in the On-line Mode, an automatic transition to the Bypass (UPS/SMS) or Off-line (MMU), Shutdown, or Automatic Voltage Regulation Modes may occur depending on internal and external UPS system conditions.
The following paragraphs explain the various operational states of the UPS 1200:
On-line (voltage regulating/motoring) - The UPS 1200 is providing a constant voltage to the load. The UPS is drawing power from the input in order to spin the flywheels up to the speed for charging (7700 RPM). The UPS 1200 regulates voltage. When the flywheels reach 4000 RPM, the UPS 1200 can discharge.
On-line (standby) - The UPS 1200 is regulating voltage and ready to discharge the flywheels in order to protect the load. Each flywheel draws about 1 kW from the input source in order to maintain standby speed.
Bypass (UPS/SMS) - Power is going through the internal bypass circuit of the UPS 1200. The load is not protected.
Off-line (MMU) - Power is going through the internal bypass circuit MMU. The load is not protected by this MMU. The load may still be protected by another MMU.
Discharge (discharge) - The UPS 1200 has disconnected from the input and is delivering power to the load from the flywheels.
Discharge (phase match) - The UPS 1200 is still delivering power to the load but the UPS has qualified the input voltage. The UPS 1200 will match the output (frequency and phase) to the input source.
Discharge (walk-in) - Once a phase match is achieved, the UPS 1200 connects to the source and transfers the load from the flywheel to the source. At the end of the walk-in time, the UPS 1200 enters the Online (motoring) state.
Online Mode
Illustration 1 | g01265177 |
When operating in the Online mode, the system is ready to protect the load. When online, output voltage is being regulated to within ±1 percent of the nominal setpoint. The following illustrations show the system power flow when in Online, Standby, or Motoring states.
When the system is in the Online Mode:
- the Input Circuit Breaker (K1) and the Output Isolation Switch (K5) are closed
- the Bypass Static Switch is OFF
- power flow through the system is via the closed (ON) Line Static Switch and through the Line Inductor
- both Inverter Contactors (K3 and K4) are closed
- utility inverters are ON
The Inverters regulate the voltage on the DC Bus and control the reactive current through the filter inductors to regulate the system output voltage. At least two Flywheel Cabinets must be connected to the DC Bus with the disconnect switches closed in order for the system to operate in the Online Mode.
Note: Only one Flywheel Cabinet is required if the UPS 1200 is lightly loaded.
Online Mode States
There are three states within the Online Mode:
Online-Charging - The system enters this state when 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.
Online-Standby - When all system flywheels reach a speed of 7700 RPM, the system is in the Online-Standby state.
Note: 7700 RPM is the flywheel idle speed.
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Online-Discharging - The system enters this state when the Flywheel Cabinets are supplying power to the load. The system automatically enters this state when utility power is disrupted. Illustration 2 shows the UPS 1200 power flow when in the Online-Discharging state.
Illustration 2 | g01265185 |
Online Discharging State
When the system is in the Online Mode Discharge State, the Input Circuit Breaker (K1) may be open or closed. The Input Circuit Breaker is closed when the system first starts discharging, but opens if the outage lasts for more than five (5) seconds. The Line Static Switch is OFF, and power is flowing out of the Flywheel Cabinets. The Flywheel Cabinets regulate the voltage on the DC Bus, and the Utility Inverters convert the DC Bus voltage to three-phase AC voltage, which is supplied to the load. The Bypass Static Switch is OFF and the Output Isolation Switch (K5) is closed.
Bypass Mode (UPS/SMS)
Bypass Mode directly connects the incoming utility power to the load while bypassing the UPS system. Illustration 3 shows system power flow when in Bypass Mode. The load is not protected when the system is in Bypass Mode and can be affected by a disruption of the incoming power.
When the system is in Bypass Mode, K1 and K5 are closed. Power flow through the system will be via the Bypass Static Switch, which will be ON. The line static switch is OFF and the Inverter Contactors K3 and K4 are open.
The system enters Bypass Mode for any of the following reasons:
- system start-up
- operator command via Graphical User Interface or monitoring software
- failure to recover from a fault
Repeated errors causing the system to switch between Bypass and Online Modes can lock the system in Bypass Mode. When the system is locked in Bypass Mode, the operator must intervene to bring the system back online. Bringing the system back online is done either via the Graphical User Interface or the monitoring software.
Note: The UPS 1200 will fail to start when in Bypass Mode if any of the following Notices are present: Unacknowledged, Active and Alarm. Use the Events screen to acknowledge Notices and Alarms and to correct any Active Notices or Alarms so the UPS 1200 will start up.
There are two important Bypass Mode states:
Bypassed-Offline - Bypassed-Offline is the state the system enters when commanded to bypass via operator input, or when the system has been locked into bypass because of a fault condition. The system can only leave this state when commanded by an operator via the Graphical User Interface or monitoring software.
Bypassed-Verify Signals - When in this state, the system is verifying that the correct system telemetry is present. This state is used when starting the system and when recovering from errors. Bypassed-Verify Signals is the state the system stays in if an operator tries to bring the UPS 1200 online and there are unacknowledged events in the event log.
Bypass Assist Mode (MMU)
Bypass Assist Mode directly connects the incoming utility power to the load while bypassing the MMU. Bypass Assist Mode provides a fast transfer to bypass and maintains power to the load while the bypass breaker in the parallel switch gear closes.
Illustration 3 | g01265188 |
Illustration 3 shows system power flow when in Bypass Assist Mode. The load is not protected when the system is in Bypass Assist Mode and can be affected by a disruption of the incoming power.
Offline Mode (MMU)
When the system is in Offline mode, K1 and K5 are closed. Power flow through the system will be via the Bypass Static Switch, which will be ON. The line static switch is OFF and the Inverter Contactors K3 and K4 are open.
The system enters Offline Mode for any of the following reasons:
- system start-up
- operator command via Graphical User Interface or monitoring software
- failure to recover from a fault
Repeated errors causing the MMU to switch between Offline and Online Modes can lock the MMU in Offline Mode. When the MMU is locked in Offline Mode, the operator must intervene to bring the MMU back online. Bringing the MMU back online is done either via the Graphical User Interface or the monitoring software.
Note: Unacknowledged or Active Notices or Alarms keep the MMU from starting up in the Offline Mode. Use the Events screen to acknowledge Notices and Alarms and to correct any Active Notices or Alarms so the MMU will start up.
Automatic Voltage Regulation Mode
Automatic Voltage Regulation is an operating mode where the output voltage is regulated to the nominal setpoint. The power factor and harmonic benefits of the UPS/SMS or MMU are also still present in this mode. However, the load in and UPS/SMS system is not protected when the system is in Automatic Voltage Regulation Mode which will be indicated on the Graphical User Interface (One-Line) display. If an MMU in a Paralleled UPS system is in Automatic Voltage Regulation Mode, the load may or may not be protected, depending on the state of other MMUs in the system. When in Automatic Voltage Regulation Mode, the Graphical User Interface (One-Line) will also display the mode as "Regulating".
Automatic Voltage Regulation Mode can be entered for any of the following reasons:
System start-up - When the SMS/MMU is transitioning from Bypass/Offline to Online, the system transfers from Bypass/Offline to Automatic Voltage Regulation Mode and then begins to motor (or preheat) the flywheels. The system will remain in Automatic Voltage Regulation Mode until there are enough flywheels above 4000RPM to support the load connected to the output of the UPS 1200.
Flywheel errors - There are not enough flywheels available to support the load connected to the output of the UPS 1200.
Flywheel Cabinet keyswitch in the spin down position. - There are not enough flywheels available to support the load connected to the output of the UPS 1200.
Shutdown Mode
When the UPS/SMS or MMU is in the Shutdown Mode, K1 is open. There is no power flow through the UPS/SMS or MMU when the system is shut down and no power is supplied from the system to the load. All contactors are open, and both static switches and utility inverters are OFF.
Shutdown Mode can be entered for any of the following reasons:
- An Emergency Power Off has occurred. An Emergency Power Off occurs when you press either the "EPO" button on the front of the Controls Cabinet or a remote Emergency Power Off Button (if installed).
- There are internal or external conditions that could lead to system failure.
Operator intervention is required to put the system back online if it is shut down. If an Emergency Power Off has occurred, there is a reset switch located behind the door on the Controls Cabinet that needs moved to the "I" position or "Green" position.
Note: An Emergency Power Off from the Parallel cabinet in a Parallel system does not trip the reset switch in the MMUs. Refer to the Parallel Control Cabinet (PCC) manual to reset the system after an Emergency Power Off.
The Emergency Power Off Button is located on the front of the Controls Cabinet, directly below the Graphical User Interface. Pressing the "EPO" button transitions the UPS/SMS or MMU to the Shutdown Mode. Shutdown Mode opens the K1 input circuit breaker and:
- removes power from the load in an UPS/SMS system or
- removes the MMU from the array in a Paralleled MMU system.
When the emergency power off switch is used, high voltage still remains in the system. |
A qualified electrical professional must restart the system after an Emergency Power Off event.
Press either of the following buttons to activate an emergency shutdown:
- Emergency Power Off Button - Controls Cabinet
- Remote Emergency Power Off Button - Optional Location