The thermal protector is most likely to be used in electric motors of the three-phase type, although only in motors with a Y-connection. Convenience concerns a combination of current and temperature-sensitive protector and reclosing guarantee automatic.
The drawbacks refer to current limitation, because the protector is directly connected to the coil of the single-phase motor and the application is aimed at three-phase motors. After reaching a lower temperature than specified, this protector must be reclosed.
When dealing with phenolic thermal protectors, they are based on bimetallic disks, which have two moving contacts, as well as a resistance and a pair of fixed contacts. The protector is properly driven in series and, due to the thermal dissipation caused by the passage of the chain, a deformation of the disc occurs, causing the contacts to open and the motor supply to stop. FB-810-8
The protectors are bimetallic elements that have normally closed contacts, used in single-phase induction motors, in order to avoid overheating caused by overloads, causing the rotor to lock, as well as voltage drops.
When the generator is connected to the mains momentarily, the voltage to its terminals will be indicated by the frequency of rotation and by the number of poles, resulting in the frequency of the three-phase voltage of the machine.
In order for the synchronous machine to transform the mechanical energy applied to its shaft or shaft, it is necessary for the field winding located in the machine rotor to be supplied by a source of continuous voltage, so that, when performing the rotation, the magnetic field caused by the rotor poles to have a relative movement to the conductors of the stator windings.
It is worth remembering that in performing functions as a generator, mechanical energy is produced and supplied due to the machine by the application of a torque and by the rotation of the shaft or shaft thereof. In this way, the mechanical energy source can be a hydraulic turbine, gas or steam. helical gear boston
Because of the relative movement between the magnetic field of the rotor poles, the intensity of the magnetic field circulating through the stator windings may change over time, and according to the ohm law, voltage induction will occur to the winding terminals of the rotor. stator.
Today electric motors are present in almost every industrial, commercial and residential facility and as an example, we have the tiny motors that connect the hard drives of the computers, the variety of motors that connect our appliances and the large motors that move ventilating pumps , mills, compressors, and other diversities of applications.
The design and research of enamelled conductors, synthetic insulation papers or films, magnetic sheets, aluminum alloys and plastic materials basically cooperated for the weight to power ratio of the motors. Analyzing the weight of a motor of the same power with the passage of time, we can verify that the current motor has only 8% of the weight of its precursor in 1891.
By comparing catalog data from different manufacturers at different times, we can see that there was a reduction in weight and, consequently, a decrease in the engine’s constructive size by approximately 20% in each decade, taking the last two, in which the reduction was less defined. RL32013B1
This demonstrates the necessity of periodic revision of the norms, in order to adjust the relation between powers and carcasses to the sizes reached through technological development. This technological development is fundamentally characterized by the creation of new insulating compounds, which tolerate higher temperatures.