Examining the advantages and disadvantages of normally open contactors versus normally closed relays reveals distinct characteristics. Normally open contactors, while cost-effective, exhibit a notable drawback—requiring continuous energization when the load is active, roughly 99% of the time. This constant energization leads to audible humming, buzzing, heat generation, and a higher failure rate compared to devices not consistently powered.
On the other hand, normally closed relays operate in opposition to contactors, being energized only when the load is disconnected. This approach mitigates issues related to constant energization but comes with the drawback of being economically available only up to 50 amps. Despite their precision and fail-safe operation, the limited load capacity may influence their suitability for specific applications.
Choosing between normally open contactors and normally closed relays depends on the specific requirements of the application, considering factors such as cost, heat generation, noise tolerance, and load capacity.