The thermal protector consists of a bimetallic disc, which contains two moving contacts, plus a resistance and a pair of fixed contacts. The protector is driven in series and due to thermal dissipation, which is generated by the passage of the current, through the internal resistance, a deformation of the disc can occur, resulting in the opening of the contacts and thus causing the motor power to stop .
After a lower than specified temperature has been reached, this protector must be reconnected. Depending on this process, two types of protectors can be used, one with automatic reclosing and the other with manual reclosing. These protectors are basically bimetallic type devices which have normally closed contacts, used mainly in single-phase induction motors, in order to protect against overheating caused by overloads, causing the rotor locking and voltage drops.
The thermal protector is applicable to electric motors GLP3348 of the three-phase type, but only to Y-connected motors. The advantages are a combination of current and temperature-sensitive protector. The drawback is the current limitation by the protector being directly connected to the single-phase motor coil.
In 1820, the Danish scientist Hans Christian Oersted did not imagine that with a simple experiment he would discover a physical principle of extreme importance for the operation of this type of motor. In this way, the scientist passed an electric current, produced by a normal heap, by a conductor wire and soon after approaching a compass of that wire. The needle, which acts magnetically, moved and aligned perpendicular to the thread. For Oersted, the event confirmed that around the wire, had a magnetic field, which acted on the field of the needle.
Thus, the relationship between magnetism and electricity was first established. The French physicist André-Marie Ampere, a genius of mathematics, after knowing the experiences of the Dane, began to create a law of electromagnetism, understanding that the lines of force created by the electrified wire, the magnetic field, are circular, that is, Form a kind of invisible cylinder around the driver. T2535173S
Up until now, the magnetic field had been thought to move only in a straight line, as from one magnet to another. In the connection between electricity and magnetism, there was Englishman Michael Faraday. He valued experience as evidence of natural phenomena. It was thanks to his experiences and his curiosity, he was able to demonstrate in 1822 the circular magnetic field.