Joint research project between DSM and ERDA confirms prime position for high performance polyamides in safer circuit breakers
1/8/2015
Royal DSM, the global Life Sciences and Materials Sciences company, says that new independent research with Electrical Research & Development Association (ERDA), a cooperative research institution in India, shows that the use of DSM's high performance polyamides in molded case circuit breakers (MCCBs) makes them safer and more cost-effective to produce than traditional versions made in thermoset composites. MCCBs are heavy duty circuit breakers, mostly used in industrial and commercial buildings, and operate at far higher electrical ratings than miniature circuit breakers, MCBs, used in domestic housing.
DSM is the first engineering plastics supplier to offer a full portfolio of materials for MCCBs. It has solutions for all the separate housing components, as well as for the functional internal parts in the arc extinguishing chamber, which are critical components in MCCBs, resulting in a very safe and cost-effective solution. The results from the latest research confirm the advantages of DSM engineering plastics, and have given a strong indication of the extensive possibilities they offer in this growth market.
The company has been collaborating for over a year with ERDA (Electrical Research & Development Association), a cooperative research institution created by the Indian electrical industry and utilities to cover basic research in the field of electrical applications. ERDA has helped DSM improve its understanding of the thermo-mechanical and electrical performance of thermoplastics in arc chutes.
DSM has been a pioneer in replacing thermosets in low voltage switchgear (LVSG) applications such as MCBs for over 35 years. Now, with its most recent developments in high-performance, halogen-free flame-retardant materials, and the support of this independently-verified performance data, the company intends to repeat its success in MCCBs. It is in a strong position to demonstrate the benefits of its highest performing grades in the arc chute. Selected DSM partners such as Jiangsu Phono Electrical Co. Ltd. in China are in fact already commercializing the concept.
Alexis Ponnaradjou, VP Global Research and Technology for Engineering Plastics of DSM says: "We were very confident from the outset that our cooperation with ERDA would lead to innovative solutions on performance and sustainability, and I am happy to say that the results from our joint research have shown that our confidence was well-founded."
Research at ERDA has confirmed that arc chutes injection molded in thermoplastics such as halogen-free UL94 V-0 flame retardant types of DSM's Stanyl® polyamide 46 could easily withstand the thermo-mechanical and electrical stresses developed during short-circuit in MCCBs with breaking capacities up to 25 kA. But the same concept could potentially be used in MCCBs with much higher breaking capacities. In addition, polyamide 46 provides increased safety margins over thermosets, even in parts with far lower wall thicknesses.
The primary function of the arc chute is to provide final cooling of the arc, in order to help avoid an arc re-strike, and preserve the integrity of the contacts to increase the service life of the MCCB. Until now, arc chutes have been made in thermoset composites (DMC/BMC). The production process is longer than with thermoplastics, reject rates are generally higher, and the materials cannot be melt-recycled. Thermoplastic versions can also be designed with increased functionality built into them, compared to thermosets.
DSM's high-performance, high-temperature resistant Stanyl polyamide 46 has an additional advantage: it emits gases when exposed to high temperature and UV radiation from the plasma generated by the arc, thus providing extra help in rapid cooling of the arc, reducing carbonization and contact pitting.
In their research project, DSM and ERDA looked at the performance of various flame retardant aliphatic high temperature polyamides in short-circuit and electrical endurance tests on a single pole MCCB, rated up to 25 kA breaking capacity and up to 100 A nominal current. Materials included Akulon® PA66, which has a melting point of 255ºC and a maximum continuous-use temperature of 180ºC; and Stanyl PA46, which has a melting point of 295ºC and a maximum continuous-use temperature of 230ºC.
The researchers concluded that thermoplastic arc chutes could withstand transient as well as normal conditions, and also helped to decrease the arcing time and energy dissipated in the MCCB. As a result, there was far less carbonization than with thermoset arc chutes, helping to improve the long-term performance of the MCCB.
The experiments confirmed that flame retardant glass filled Stanyl arc chutes gave the best results in short-circuit tests. Even though unfilled grades could release far more off-gasses, and so were better than filled ones for arc voltage and carbonization, the reinforced Stanyl showed much higher thermo-mechanical stability and lower degradation. It is therefore seen as the best choice, considering the long life expectancy and performance repeatability required from MCCBs in the field.
The two partners now plan to take their cooperation further with a third partner, engaged in manufacturing of instrument transformers. Together, they will research the design and development of new challenging switchgear applications that have still not been converted from thermosets to thermoplastics.
More information can be found at www.dsm.com/electrical-electronics and www.stanyl.com.
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