MGE UPS Systems 6000 manual Static bypass, Discrimination and short-circuit capacity

MGETM GalaxyTM 6000 : Specification guide

Parallel UPS, three-phase, 250 to 3000 kVA*

*Power rating for an N+1 redundant configuration

5.3.3- Synchronisation with bypass power

ω When bypass power is within tolerances

To enable transfer to bypass power (see conditions below in section 5.4 "Static-bypass"), the inverter output voltage shall be synchronised with the bypass source voltage whenever possible. To that end, during normal operation, a synchronisation system shall automatically limit the phase deviation between the voltages to 3 degrees, if the bypass source frequency is sufficiently stable (within adjustable tolerances of ± 0.5 Hz with respect to the rated frequency).

ω Synchronisation with an external source

It shall be possible to synchronise with all types of external source.

For example, if the bypass source is a generator set, the synchronization tolerances shall be approximately

± 2 Hz (adjustable).

ω Autonomous operation following loss of synchronisation with bypass power

When the bypass source frequency deviates beyond these limits, the inverter shall switch over to free-running mode with internal synchronisation, regulating its own frequency to within ± 0.1 %. When bypass power returns to within tolerances, the inverter shall automatically resynchronise.

ω Variation in frequency per unit time

To avoid transmitting to the inverter any excessive frequency variations on the bypass AC source when it is within tolerances, inverter frequency variations per unit time (dF/dt) shall be limited to 1 Hz/s or 2 Hz/s (user defined).

5.3.4- Overload capacity

The UPS shall be capable of supplying for at least:

ω1 minutes a load representing 165% of the rated load;

ω1 second a load representing 200% of the rated load.

If necessary, the UPS shall operate as a generator (current limiting) with a peak capacity of 233% for 150 milliseconds, to allow highly disturbed transient operating states (high overloads, very high crest factors, etc.) without transferring the load to the bypass.

5.4 - Static bypass

5.4.1 - Load transfer to the static bypass

Instantaneous transfer of the load from the inverters to bypass power and back shall take place without a break or disturbance in the supply of power to the load, on the condition that the bypass source voltage and frequency are within the tolerances specified in section 4.1 "Bypass AC source" and that the inverters are synchronized. Transfer shall take place automatically in the event of a major overload or an internal UPS-system fault. Manually initiated transfer shall also be possible.

If the bypass power is outside the specified tolerances or is not synchronized with the inverters, automatic transfer of the load from the inverters to bypass power shall be inhibited or shall take place after a calibrated interruption of 500 to 800 milliseconds.

Manual initiation of this transfer as well as transfer back to the inverters shall also be possible.

5.4.2- Static-switch protection

The static switch

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[ common centralized-bypass ] () with centralized-bypass cabinet)

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[ in each UPS unit ] (other cases)

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shall be equipped with an RC filter for protection against switching overvoltages and lightning strikes.

5.5 - Discrimination and short-circuit capacity

If the bypass power is within the tolerances specified in section 4.2 "Bypass AC source" section, the presence of the static switch

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[ common centralized-bypass ] () with centralized-bypass cabinet)

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[ in each UPS unit, supplied by the same bypass AC source ] (other cases)

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shall make it possible to use the short-circuit power of the bypass source to trip the downstream protection devices of the inverter.

To ensure tripping in a selective manner, the available power shall be sufficient to trip protection devices with high ratings (circuit breaker rated In/2 or UR fuses rated In/4, where In is the rated inverter current).

If the bypass source is outside the specified tolerances, the inverter on its own shall, for the same discrimination requirements, be capable of tripping circuit breakers rated In/2 or UR fuses rated In/4, irrespective of the type of short-circuit.

APC By Schneider Electric Edition - 03/2009 Spec. E - 8