Three Pole Electric Motor

The invention relates to an alternating current motor supplied with a single phase and having three poles and two coils, a condenser being provided in the circuit of one of the two coils.

It is known to provide an electric single-phase motor with three magnetic poles and two coils, one of the coils being directly connected to a single-phase alternating current supply while the other coil is connected to the same supply in circuit with a condenser. This condenser requires complex connections and makes the dimensions of the coil in circuit with the condenser depend upon the supply voltage.

It is the object of the invention to provide an improved three-pole, two-coil single-phase energized alternating current motor.

According to this invention a motor with three poles has one of its coils connected to the alternating current supply system and a second coil tapped across a portion of the first coil in circuit with a capacitor or merely bridged by the capacitor.

In the drawing:

FIG. 1 is a diagram of one connection arrangement of a motor according to the invention; and

FIG. 2 is a diagram illustrating a second connection arrangement of the motor according to the invention.

The motor according to the invention comprises a magnet-core stator 1 provided with only three poles, 1, 3, 4 extending all around and with air-gap spacing from a cage-type rotor 7. The two poles 2 and 3 each is formed with a respective outer column of the stator while the pole 4 is formed with a central stator, the three columns being parallel to one another and bridged at their ends remote from the rotor. The coil 5, wound upon one of the outer columns is connected across the terminals of a single-phase alternating current supply source 8.

In the embodiment of FIG. 1, the terminals of the other coil 6, wound upon the other outer column, are bridged directly by a capacitor 9 without any galvanic connection to the source 8.

In the embodiment of FIG. 2, however, the coil 6 is taped across a portion of the coil 5 in circuit with the capacitor 9.

In the embodiment of FIG. 1, the flux induced in the core 1 by the coil 5 is split through the central column and the outer column and induces a current in coil 6 provided with the capacitor 9.

Because of the shape of the magnetic core 1, the leakage reactants of the coils (including coil 6) is relatively large so that the circuit may reach a resonance or ferroresonance condition. The capacitor 9 dephases the current in the circuit including coil 6 so that the fluxes induced by the coils 5 and 6 are out of phase. The out-of-phase fluxes are superimposed on the central column to produce a resultant third phase whereby the stator is magnetically energized in a tri-phasal system, the first phase of which is the flux phase induced by coil 5, the second phase of which is the shifted phase of coil 6 and the third phase of which is the superimposed phases of pole 4. The resulting rotating field in the air gap drives the rotor 7. The three pole motor may have the parallel columns illustrated although it is possible that the columns are tilted at 120.degree. to one another.

The invention is advantageous because of the simplified connection and because it enables the second coil 6 to be dimensioned independently of the supply voltage.