A. the harm of harmonics generated by the UPS power supply
1. UPS power supply harmonics may cause ammeter, voltmeter, power meter, power meter measurement errors, so that the lighting facilities to shorten the life.
2. making the distribution line loss becomes larger, heat, shorten the life of the insulator, and may even cause a short circuit or fire.
3. Interference to circuit breakers, leakage protectors, relays and other protection, automatic control devices and other instruments, causing misoperation. Make the motor produce additional loss and heat, generate pulsating torque and noise.
4. Produce electrostatic interference and electromagnetic interference to the adjacent communication lines, cause static electricity in the distribution system, and may cause series/parallel resonance of compensation capacitors.
B. the approach to suppress harmonics
1. using 6 pulse UPS power supply and active harmonic filter, input current harmonics "5% (rated load), input power factor 0.95. This configuration, although the input indicators are very good, but the technology is still not very mature, there are miscompensation, over-compensation and other problems, resulting in the main input switch false tripping or damage and other phenomena.
2. using 12 pulse UPS power supply +11 harmonic filter, such as UPS power rectifier for three-phase fully controlled bridge 12 pulse rectifier, plus 11 harmonic filter reduced to less than 4.5%, can basically eliminate harmonic current content of the harm to the grid, the price is relatively cheap active filter.
3. the use of phase-shifting transformer + 6 pulse rectifier false 12 pulse program, the composition of two 6 pulse rectifier UPS power supply patchwork into.
