Powerware SOLA 4000 manual Battery Accumulator, Inverter, Static Switches

SOLA 4000 - General System Description

1 UPS Assembly

1.4 Battery (Accumulator)

The battery supplies power in case of a short interruption or a total breakdown of the ac mains supply. In case of a rectifier failure (no dc voltage output), the load will be fed by the battery.

The battery is only capable of feeding the load for a certain time (autonomy time), depending on battery capacity and actual load.

The number of cells within the battery depends on the battery type and may also vary due to specific customer requirements. The standard number is 192 cells for lead-acid batteries and 300 cells for NiCd batteries. The battery capacity (Ah) depends on the UPS output power and the required autonomy time. The battery of 10- 30kVA units is installed inside the UPS cabinet as standard. For 40-120kVA units (or 10-30kVA units with extended battery au- tonomy), batteries are installed in external battery cabinets.

1.5 Inverter

The inverter converts dc voltage supplied by the rectifier or battery to ac voltage of a precisely stabilised amplitude and frequency that is suitable for power supply to most sophisticated electrical equip- ment.

The inverter output voltage is generated by sinusoidal pulse width modulation (PWM). The use of a high carrier frequency for the PWM and a dedicated ac filter circuit consisting of the transformer and capacitors, ensure a very low distortion of the output voltage (THD<1% on linear loads).

Every phase voltage of the inverter output is controlled separately, thus ensuring constant and equal UPS output voltages even with highly unbalanced loads.

The inverter is designed specifically for the application of today's loads i.e. The output harmonic distortion will be maintained at low levels due to a unique adaptive correction technique, even with the application of highly distorted loads.

The inverter control logic restricts the maximum output current to 150% of the nominal current in case of a short circuit. In case of overload (up to 125% of the nominal current), the output voltage is maintained constant. For higher currents the output voltage is reduced, however, this will only occur if the bypass supply is not available. Otherwise the UPS will switch to bypass operation for currents higher than 110% of the nominal current.

The inverter IGBT transistors are fully protected from severe short circuits by means of a desaturation monitor or "electronic fuse".

1.6 Static Switches

The block diagram illustrates the two static switch sections that use thyristors as switching elements. During normal UPS operation, SSI is closed and SSB is open, thus connecting the load to the inverter output.

JUE 401264 8