UPS (uninterruptible power supply system) part02

3. Bypass operation

This part of the system enables the consumers to be changed over to direct mains power supply (bypass mains) without interruption and adhering to the specified tolerances. The change-over can be initiated automatically by a control signal, or manually.

Every interrupt-free change-over, whether automatic or manual, is only possible if voltage frequency and phase angle of the UPS system are synchronized with the bypass mains' Deviations in the mains frequency outside the specified tolerances inhibit the change-over.

Automatic change-over of the consumers to the bypass mains is effected when the power supply within the specified tolerance is not assured by the UPS system.

If a mains failure occurs during bypass operation, the system will automatically switch to battery operation without loss of output voltage, if battery is available and within tolerance.

4. Standby / Off

The load is not supplied with energy.

Manual bypass (Service Bypass)

For repair and maintenance work the system can be set to bypass with the overlapping manual bypass switch. In this way the system is volt-free, with the exception of a few elements at the connecting branch.

At the position TEST" it is possible to make transfer tests (Inverter - Bypass - Inverter) without disturbing consumers at the busbar.

3 REDUNDANT UPS SYSTEM WITH MAINS BYPASS

3.1 CONFIGURATION

The redundant UPS system in parallel operation with mains bypass consists of 2 rectifiers, 2 inverters and 2 electronic changeover units EAN with the static switches EA and EN. In addition 2 manual service bypass switches with 

overlapping action is installed. A transformer or a mains voltage regulator (stabilizer) may optionally be used in the bypassmains line.

3.2 PRINCIPLE DIAGRAM

DESCRIPTION OF OPERATION

At parallell/redundant operation the system in parallel is informed which operational mode the other system requests. This causes that the system automatically changes to the same operational mode depending on the priority succession. In case of a fault or switching, a system in parallel cannot force another system to a higher priority, that the system permits itself.

If a fault arises in a system in parallel causing that the system must switch over to a lower priority, the system will automatically turn off, if the other system can manage the load. If the other system cannot manage the load, both systems switch over to a lower priority operation mode.

LOAD SHARING

When both UPS systems operate in either normal operation or in battery operation the total load of the parallel/redundant UPS system is distributed in the way that each UPS system runs at 50% of its rating.