The basis of our harmonic mitigation system is the Harmonic Suppression System (HSS®). Instead of filtering or accommodating the flow of 3rd harmonic currents after they are generated, the patented HSS prevents the generation of those currents. The HSS consists of a parallel resonance LCR circuit tuned to a specific frequency. A property of this circuit is that it has a near infinite impedance at the tuning frequency (prevents the flow of that frequency) and a very low impedance at all other frequencies (allows them to freely flow) in the system.
Computers and other electronic devices use switched mode power supplies (SMPS) to convert the AC current to the DC current they need to operate. These power supplies, due to their design, draw current in spikes and that generates harmonic currents. Harmonics currents are generated by the load, take up space in the electrical distribution and do no useful work. They reduce the capacity of the system and generate heat thereby wasting energy.
One harmonic current, the 3rd, due its frequency and the design of electrical systems in the United States, is additive in the neutral. Thus, if each phase wire is carrying some 3rd harmonic current, the neutral wire would be carrying the sum of all three phases. More current is flowing in the neutral than in the phases and the result is overheated neutral wires, switchgear, and transformers. When the 3rd harmonic current returns to the transformer it circulates in the primary winding and is dissipated as heat. This can lead to failure of some parts of the distribution system and waste heat energy loss in the transformer that can increase electrical costs by as much as 8%.
Several methods have been employed to try to accommodate the higher currents caused by 3rd harmonics in the phase and neutral wires.
- The system can be over-sized with a larger transformer, switchgear and wire.
- The neutral wire can be doubled in size to enable it to carry the extra harmonic current.
- K-rated transformers, special transformers with more steel, heaver wires, and double neutral connections, designed to withstand the extra heat produced by harmonic currents, can be employed.
- HMT, harmonic mitigating / canceling transformers, ("zig-zag" transformers) are installed. These transformers cancel the 3rd harmonic currents in the secondary winding keeping them out of the primary winding. However, these transformers require oversize neutral wire because the 3rd harmonic current is still flowing in the system.
It is important to note none of these methods actually removes the 3rd harmonic current from flowing throughout the distribution system and none of them reduce 3rd harmonic waste heat and energy loss.
Rather than accommodating 3rd harmonic current, the Harmonic Suppression System keeps this current from being generated by the SMPS loads. When connected at the transformer in series with the neutral wire, the HSS prevents the flow of 3rd harmonic current into the transformer. Since no 3rd harmonic current can flow into the transformer, none can flow out on the phase wires, and the SMPSs cannot generate any.
The advantages of the HSS over "accommodation" technology are clear. The system can be "right sized," with installed capacity equal to what is really needed. Double neutral wires are eliminated. There is no need for k-rated or zig-zag transformers to handle the extra harmonic currents since these currents do not exist in the system. Waste heat caused by 3rd harmonic currents is no longer generated and system reliability is increased. Electrical power costs are reduced. Depending on the operating hours of a facility and the cost of power, energy savings can pay back the cost of the HSS over accommodation technology in one to three years. Contact us to calculate your energy savings and payback period when using HSS.
The Harmonic suppression system is passive, extremely reliable, UL certified and fully compliant with the National Electrical Code. It is the only harmonic mitigation system that "prevents" the formation of 3rd harmonic currents throughout the electrical distribution system. It is the only harmonic mitigation system that reduces waste energy and has an energy payback. It is clearly the technology of choice for solving 3rd harmonic current problems in electrical systems that power multiple computer and electric device loads and that is virtually every office, medical facility, school, call center and all high technology environments.