NEMA overloads often use melting alloy thermal overloads. Is this statement true or false?

The statement is true. NEMA (National Electrical Manufacturers Association) overload relays often utilize melting alloy thermal overloads as a means of protection for electric motors. These melting alloy thermal overloads work by using a metal alloy that changes phase from solid to liquid at a specific temperature. When the motor experiences an overload condition—exceeding the rated current for a sustained period—the heat generated causes the alloy to melt. This action opens the circuit, disconnecting the motor from power and preventing it from sustaining damage due to overheating.

Using melting alloy thermal overloads provides a reliable and straightforward method for overload protection, as the response time of the overload is related to the amount of overload current and the duration of that current. This principle is integral for applications where motors may face varying loads, ensuring safety and longevity of the equipment.

The other choices reflect scenarios that don't accurately capture the use of melting alloy thermal overloads in NEMA overload devices. Thus, affirming the use of melting alloy thermal overloads in such systems is an essential aspect of understanding electric motor protection mechanisms.