The Transformer and Electrical Co Ltd,Constant Voltage Transformers, Harmonics, harmonic Cancellation, Neutral Current Trap, rectification, Transformers, Claude Lyons, Wilflo, TEC, Chokes, Reactors, CVT, Control, Power, Marine, Ships, Panel, Railway, Furn

NEUTRAL CURRENT TRAP (3rd Harmonic Rejection Transformer)

A CASE STUDY

Table 1 Typical multi HRT site measurements.

HRT	Currents Before HRT’s Installed				Currents After HRT’s Installed
Position	Red Phase	Yellow Phase	Blue Phase	Neutral	Red Phase	Yellow Phase	Blue Phase	Neutral
Main Riser 1	8.8A	23A	5.7A	23A	6.1A	21.5A	9.4A	18A
Main Riser 2	18A	17A	5.9A	20A	7.7A	10A	10A	13A
Main Riser 3	22A	35A	51A	46A	29A	32A	40A	11A

Distribution Unit 1	31A	33A	12A	45A	20A	29A	20A	17A
Distribution Unit 2	27A	29A	38A	43A	10A	22A	30A	24A
Distribution Unit 3	17A	14A	17A	16A	14A	15A	18A	9.5A
Distribution Unit 4	19A	1A	1A	19A	14A	7.5A	7A	8.5A

Main UPS	257A	185A	120A	213A	216A	172A	144A	63A

Notes

1. The above measurements were taken at a London Bank with five floors of

computer systems.

2. In all cases the 3^rd harmonic neutral current was substantially reduced even

when the phase currents are unbalanced.

3. The total voltage harmonic distortion was reduced from over 9% to less

than 3%.

4. The UPS 3^rd harmonic neutral current has been reduced from 213A to 63A,

the complete site is running cooler, and the phase balance and power factor

have been improved.

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