The HM-20 and HM-30 style transformers have been specifically developed for use within distribution systems having a high density of non-linear loads, i.e. personal computers, video display terminals, fax machines, copiers, electronic high efficiency ballasts, UPS systems, variable speed drives, various electronic monitors. The nature of all these loads is non-linear; they only demand current during part of the cycle and/or change their impedance during the voltage cycle. These loads create harmonic currents, which in turn generate heat in the distribution equipment, neutral conductors and distribution transformers.

Numerous methods have been incorporated to deal with the effects of this phenomenon on the transformers in the circuit:

1. The transformer can be oversized. This not only results in a higher cost for the transformer initially, but a higher cost of operation for the life of the transformer. It's a classic case of treating the symptom not the cause.

2. The transformer can be specifically designed to withstand the effects of the harmonic currents generated by the loads. The K-rated transformer was developed to fulfill this task. Various K-ratings were established and described by the standards to deal with specific levels of harmonic currents. When properly applied, K-rated transformers provide a lower initial and operating cost. However, they can still be seen as simply a better method of treating the symptom.
3. The Olsun HM line of transformers incorporates design features that treat the causes of harmonic distortion. The secondary windings are configured to provide a phase shift with a low zero sequence impedance to provide a harmonic cancellation element. Electrostatic shielding is provided to minimize the broadcast of electrical noise from either the primary or load side to the other. The result is a transformer that can continuously carry its rated load and perform with maximum efficiency with load profiles up to K-20 with the HM-20 model and K-30 with the HM-30 model.

Standard Features of the Olsun HM Series Transformers

* Ratings - Through 5000 KVA and 34.5 KV
* Conductor and electrostatic shield material - Copper
* Temperature rise at full load - 115º C above 40º C maximum ambient (80º C available)
* Insulation system - UL listed, Class R, 220º C insulation
* Overload ability - 15% Continuous
* Zero Sequence Impedance and Reactance - less than 0.95% and 0.3% respectively
* Impregnation - Vacuum Pressure Impregnated (VPI) using 100% solids epoxy resin
* Electrostatic Shield – Single (HM-20), Double (HM-30)
* 200% Rated Neutral
* Thermal Switches - one per coil
* Efficiency Rating - Minimum 98%. Meets or exceeds Energy Star and NEMA TP-1 specifications
* Temperature protection - thermal switches provided in each coil
* Harmonic Cancellation - 3rd harmonic cancellation accomplished with secondary winding design
* Enclosures - NEMA-1 standard with an ANSI 61 gray, durable powder coat finish; NEMA-3R, 4 or 12 available
* Dimensions - See "Dimension Page" link. On request, smallest size will be maintained compatible with good wiring practices, custom dimensions are available
* Surge Suppression available
* Manufactured in the United States

Third party certification - UL, CSA labeled (CE label on request)