The Start of Synchronous Motors

If we observe the operation of the synchronous motors, it is clear that the rotor must be brought to a sufficient speed close to the synchronous, in order to synchronize with the rotating field. Some means to make this happen is to use a motor coupled to the axis of the synchronous motor, which if it is induction must have at least a pair of poles less than those of the synchronous motor and the use of the compensating windings.
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When starting with compensating windings, we must short-circuit the DC winding while applying alternating current to the stator, bringing the motor to its empty speed as an induction electric motor. The short-circuit is then removed from the field and DC voltage is applied to this winding by adjusting to the current (the DC voltage level or the field resistance value can be varied) to be small . When starting under load the best way is to use a winding rotor in place of the winding in the cage on the polar faces, that is to say, the so-called winding winding type rotor, where we use coupled to the field winding, a three-phase resistance. The motor starts with all external resistance per phase and with the field winding short-circuited.

The Start of Synchronous Motors

Triple Speed Engine

A triple-speed motor is a three-phase motor that can be basically arranged in two ways, with three separate windings or a common winding with a Dahlander. The Dahlander engine is a motor with special winding that can receive two different locks, in order to change the number of poles, thus creating two distinct speeds.
The three-phase electric motor provides unequal speeds on the same axis, but constant and mostly for only one voltage value, because the available reconnections normally allow only the change of speeds. The power and the current for each rotation are different, being modified according to the intensity of the load, problem that can be solved through a frequency inverter.
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It is of the utmost importance that the Dahlander winding be opened in the second case, otherwise, induced currents will appear when the common winding is fed, which will influence the operation of the motor. Therefore, they can not happen. The reason to avoid them is that these motors have precisely the system of a three-phase transformer. The electric motors with three windings are closed in star to avoid the same problems. If you need the triangle connection, it is mandatory to stop them when not being fed.

Triple Speed Engine

Starting Methods

The moment an electric current passes through a conductor, a magnetic field is caused around it. The main concepts about magnetism that must be considered is that as an extremely important part of electricity, since in addition to the motors, the electromagnets are used in numerous electrical components. This type of engine has a simplified construction and a significantly reduced cost, as well as being very versatile and non-polluting. During its technological development, the electric motor has become one of the most relevant projections of man.
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Its purpose is basically the drive of machines, mechanical equipment and appliances, among others, no less important. Its fundamental principles of operation, construction and methods of departure must be analyzed and respected in order to ensure satisfactory application. It can be affirmed that the electric machines are completely commanded by means of keys of departure, being that the most used consist of the direct or reversing, that has as function to drive small motors; the start star triangle, which acts in the drive of large motors without load; the compensating start, able to drive large motors with load; the start with soft-starter, used to connect large motors with load; and the starter with frequency inverter, used for small and large motors.

Starting Methods