1 ventilation equipment: in order to save energy, most hospitals adopt frequency conversion blower and air conditioner. The inverter is very important harmonic source, the current total harmonic distortion rate amounts to 33% above, the harmonic pollution, will produce a large number of 5, 7 times.

2 lighting equipment: due to the hospital internal use fluorescent lamps large,thus causing serious harmonic current, the 3 harmonic is the highest, when a plurality of fluorescent lamps connected in three-phase four wire load, midline willflow a lot of three harmonic current, have 3, 5, 7 second harmonic wave injectiongrid.

3 computer and UPS: at present the hospital are all computer network management, computer quantity very big, moreover the server data storage system must be equipped with UPS backup power supply. Personal computerswitching power supply and UPS are harmonic source, will produce 3, 5, 7harmonics amount.

In short, low voltage power distribution system in hospital has harmonic sourceloads, will produce 3, 5, 7 harmonics large, serious pollution to power grid.Single-phase nonlinear loads will cause the three-phase imbalance, harmonicexceed the standard, neutral harmonic overload power quality problems such asharmonic, must.