Literal and Numerical Symbology

The auxiliary contacts of a contactor adopt a specific type of numbering, since the number is combined by two digits, the first digit indicating the contact number and the second digit indicating whether the contact is normally closed, one two, or normally open, three and four.

Just as each element contained in an electric control circuit has its specific graphic symbol, the numbering of the contacts and the literal representation of them also have a pattern that must be respected and followed.    2B5V64

The numbering of the contacts representing the force terminals is given as follows, one, three and five are the input circuit, line. The two, four and six are from the output circuit in the terminal. The number of the auxiliary contacts follows the following pattern: one and two are the normally closed contacts (NF), with 1 being the input and 2 being the output. And three and four are the normally open contacts (NA), with 3 being the entrance and 4 being the exit. In the relays and contactors there are A1 and A2 for the coil terminals.



The Starting Current

The two methods for decreasing the starting voltage are to provide current at the normal voltage, temporarily forcing the electric motor, to be connected to the grid, with the winding for a higher voltage, thus using the star-delta starting system and generating current below the normal voltage, by means of resistors, inductors or autotransformer.

All starting systems with reduced voltage present some drawbacks as the starter torque reduces in the ratio of the square of the voltage reduction supplied to the motor.

In order for the link between motors and a public power grid to be made, it is necessary to follow some important guidelines for this purpose, established by specific standards.

Most often, it is necessary to remove an electric motor at full voltage in order to make the most of the starting torque. If the startup at full voltage of an electric motor generates a voltage drop higher than the maximum permissible, use a starter with low voltage, taking care, however, to analyze if the torque is sufficient to drive the load.


Gear Coupling

The gear coupling is essential at times when it is necessary to slow down. It is of utmost importance to check that the axles are correctly aligned and parallel when dealing with straight gears, and in the angle of engagement, in the case of helical or conical gears. Pulley and belt couplings is a specific type of transmission applied when there is a need for a ratio of speeds between the motor and the driven load.  CA32112 L

The motors that have sliding bearings have up to three marks on the end of the shaft, bearing in mind that the center mark is the indication of the magnetic center and the other two marks of the outer part, which as it has the function of permissible axial movement limit to the rotor. The engine must be coupled so that the arrow fixed to the bearing housing is over the center mark at the time the engine is running.

Excessive tension in the belts may damage the bearings and may cause engine shaft rupture. The motors equipped with slide bearings must be driven by the coupled machine or by means of a gear unit. The sliding bearings do not leave the coupling by means of pulleys and belts.