Magna-Power Electronics' HN Series harmonic neutralizers eliminate families of harmonic components by multiplying the number of input phases with specially wound autotransformers. These transformers, in combination with equally loaded, high-power DC power supplies, offer a cost-effective solution to maintaining power quality at acceptable levels.  HN Series harmonic neutralizers are packaged in cabinetry designed to be integrated with multiple MT Series installations.

Why Neutralize Harmonics?

Input current harmonics are a by-product of nearly all power supplies. Power can only be delivered to the load if the frequency and phase of the voltage and current match. For a three phase power supply using a three phase input rectifier, the input current has a theoretical spectrum of 6n±1 where n is an integer incrementing from 1; this is known as a 6-pulse waveform. This means that a power supply with a three phase input rectifier will produce input currents at 1, 5, 7, 11, 13, 17, 19 ... times the fundamental frequency. The theoretical magnitude decays as the reciprocal of the harmonic component. The 5th and 7th harmonic components have magnitudes of 20% and 14% of the fundamental component, respectively.

Harmonics currents in power systems can find unusual paths and can cause problems if the magnitude is significant and there are loads sensitive to harmonic frequencies. For example, lighting ballasts have series connected capacitors and inductors which can be excited by harmonic currents. IEEE has introduced standard, IEEE 519, which defines recommended limits. Implementing this standard requires a knowledge of the power system and other loads producing harmonics. Unfortunately, the standard can allow the same power supply to possibly exceed limits in one application and not in another. In the same respect, a power supply may or may not can cause a harmonic related problem with or without meeting IEEE 519. The best solution to minimize the risk of a harmonic problem is to eliminate the harmonic current at the source.

Figure 1. (a) 6 and (b) 12-pulse waveforms

Magna-Power Electronics’ HN Series harmonic neutralizers suppress families of harmonics by increasing the number of power phases. It can be used when multiple power supplies are used in series or parallel and are equally loaded. Harmonic neutralizers can produce 12-pulse or 18-pulse waveforms which have harmonic current components on the order of 12n±1 or 18n±1, respectively. Figure 1 shows the theoretical difference between 6-pulse and 12-pulse waveforms; 18-pulse waveforms are similar, but with more steps. Figure 2 shows the resulting spectral differences. HN Series harmonic neutralizers are protected with appropriate sized circuit breakers.

Figure 2. Normalized input harmonic current spectrum for (a) 6, (b) 12, and (c) 18-pulse waveforms

Models and Ratings

Size: 62½" H x 24” W x 31½” D

Size Diagrams

Option Code: +HN

Products Supported: