Customer Challenge:
Using an electrical insulation paint is a quick and easy way to increase the capacitance in high voltage instruments, preventing unwanted short-circuits. Circuit breakers, which quickly bypass and shunt excess current when circuits become overloaded, are an example of an instrument that uses electrical insulation paint. Specifically, the arc chambers within the circuit breaker – which contains and extinguishes electrical arcs generated when excess current is delivered through the circuit breaker – are constructed with insulating materials such as plastics and composites. Extra layers of insulating coatings are often applied because the material can splinter over time due to the heat and pressure of the chamber, leading to a reduction in insulation resistance.
For this customer, the challenge was finding a single component coating that cured at room temperature, bonded to ABS and had sufficiently high dielectric strength to bolster the insulation resistance of their arcing chamber.
Key Customer Requirements
- High dielectric strength
- Single component that can cure at room temperature
- Bonds to ABS
Solution
MG Chemicals 4226A is a single component, alkyd varnish that fully cures at room temperature. It’s highly flexible to conform to complex geometries and bonds well to a variety of substrates including many thermoplastics, metals, composites and glass. It cures to a clear finish and boasts impressive insulating properties such as a dielectric strength of 3000 V/mil, comparative tracking index (CTI) of 600 V and breakdown voltage of over 5000 V. The customer was able to apply the coating successfully to the interior housing of their arc chamber for added insulation protection that can handle current as high as 100,000 amps and voltages as high as 600 V.
Conclusion
Arc chambers, as a sub-component of circuit breakers, require high insulation in certain areas. Over time, excessive warping of the original materials can compromise the integrity of the insulation. As a result, insulating coatings like the 4226A can be applied to repair damaged areas and restore the electrical isolation.
