Basic requirements
1. Total harmonic distortion (THD) of input current (THD: the percentage of the effective value of the harmonic current of the AC current to the effective value of the fundamental component)
The THD of the input current of the 6-pulse rectifier should be less than 33% at the full load input current of the 6-pulse rectifier; By using an input filter, the input current distortion can be reduced to 10% The THD of the input current of the 12 pulse rectifier should be less than 10% at full load, and using an input filter can reduce the total harmonic distortion of the input current to 5%
2. AC input current limit
The rectifier/charger should have an AC input current limit circuit, which generally limits the AC input current to 115% of the full load input current.
. When the generator set is powered (at which point the rectifier will receive an external low voltage signal, which determines that it is powered by the generator set), the AC input current should be limited to 100% of the full load input current3. Battery charging current limit
The rectifier/charger should have a battery charging current limit circuit to limit the battery charging current to 15% of the rated output capacity (KW) of the UPS.
. When supplying power to the generator set (when receiving an external low voltage signal), the charging current of the battery should be limited to zero4. Temperature compensation for battery charging voltage
When using a remote temperature detector, the rectifier/charger should automatically adjust the battery float charging voltage (generally -5mv/unit/℃). Usually, the float charging voltage of the battery is 2.25V/piece, and the termination voltage is 1.67V/piece. Therefore, the DC bus voltage is N for float charging and termination voltage, respectively × 2.25V, N × 1.67V (N represents the number of batteries)
5. Gradual increase of input power
The rectifier/charger should have the ability to limit the initial power requirement to 20% of the rated load and gradually increase the input power to 100% of the rated capacity within a 10 second time interval.
. In a redundant UPS system, the input power of each rectifier/charger should be delayed by 5 to 300 seconds to reduce the impact on the generator set6. Input isolation switch
The rectifier/charger should have an input isolation switch and protection. The isolation switch should be able to provide both the current that meets the load and the recharge current of the battery, and can withstand large short-circuit currents
7. DC Filter
The rectifier/charger should have an output filter to minimize the ripple voltage applied to the battery.
. The AC ripple voltage of the DC output voltage of the rectifier should be less than 1% of the floating charge voltage (RMS). The filter should fully ensure that the DC output voltage of the rectifier/charger meets the requirements of the inverter when the battery is not connected Recharging of the batteryFunction of testing report:
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