Introduction (cont.)
Operation with an engine generator set
See figure 15 below.
If a
With such a system, the required battery time may be reduced to the time necessary for starting and bringing on line the
(D)supplies power to the inverter (B) during the transfers:
◗ normal AC source to the generator; ◗ generator to the normal AC source. The transfer sequences described above (normal AC source ➜ battery, battery ➜ generator, generator ➜ battery, and battery ➜ normal AC source) are fully automatic. They in no way affect the load and require no manual operation by the user.
Note:
To avoid load surges on the generator, the rectifier/charger is started with a 10 second maximum current consumption
To avoid overloading an undersized engine generator set, it is possible to set a maximum power level drawn by the normal AC input. Any additional power required is supplied by the battery. This modification can be made on site by an APC by Schneider Electric technician.
Output voltage quality and continuity
The output voltage is stable in amplitude and frequency and is free of interruptions or transients outside specified tolerances, irrespective of normal AC source or load disturbances (outages, load step changes, etc.).
Steady state voltage regulation
For stable or slowly varying load conditions, the inverter output voltage is regulated to within ±0.5% in amplitude. The frequency of the output voltage can theoretically be regulated to within
0.1% of the rated value, however the output frequency range may be intentionally extended to a maximum of ±2 Hz so that the inverter can remain synchronised with the bypass AC source and its inherent frequency fluctuations, thus enabling transfer of the load to the bypass line at any time.
Note:
The output frequency range can be personalised and if necessary modified on the customer site by a qualified APC by Schneider Electric support technician from ±0.25 Hz to ±2 Hz in 0.25 HZ steps.
When the bypass AC source voltage moves outside this frequency range, the inverter is desynchronised and operates in "free running" mode, with the output frequency regulated to a high level of accuracy by a quartz oscillator.
When the bypass AC source frequency returns to within the specified tolerances, the inverter is gradually re- synchronised to the bypass line at a rate of 0.5 Hz to 2 Hz/s (as per the value personalised by the
Transient voltage regulation
The inverter output voltage is not notably affected by instantaneous major variations in load characteristics. This is made possible by the PWM (Pulse Width Modulation) chopping technique and the microprocessor- based regulation system that instantly compensates for any variation. In particular, the inverter output voltage remains within +/- 2% of the rated voltage for load step changes of 0 to 100% or of 100 to 0%.
Example of an installation with an engine generator set
| MGE™ Galaxy™ PW |
|
generator | main LV switchboard | C |
G | Mains 2 |
|
|
| |
| A | B |
HV system | Mains 1 |
D
Fig. 15