WO2007074081A1

WO2007074081A1 - An electric motor

Info

Publication number: WO2007074081A1
Application number: PCT/EP2006/069739
Authority: WO
Inventors: Latif Tezduyar; Fehmi Sonmezoz; Kerem Erenay
Original assignee: Arcelik Anonim Sirketi
Priority date: 2005-12-29
Filing date: 2006-12-15
Publication date: 2007-07-05
Also published as: EP1966883A1

Abstract

The present invention relates to an electric motor (1) which can be operated at variable speeds. In the electric motor (1) of the present invention, the relays (5) are situated between the windings (4) in all the phases (7) except one phase (7), and the by-pass lines (6) extending from the relays (5) are connected to the connection point (Y) between the two windings (4) of the last phase (7).

Description

AN ELECTRIC MOTOR

The present invention relates to an electric motor which can be operated at variable speeds.

Electric motors are basically composed of a stator comprising windings situated over a stack formed of laminations and a rotor having a magnet that rotates in proportion to the frequency of the feeding current and a shaft that transfers the rotational movement.

The electric motors used in household appliances need to be operated at variable speeds. For example, the brushless direct current electric motor used in the washing machines is operated at a higher speed in the spin drying step than in the washing step. In a three phase electric motor having star type winding connection, the speed of the electric motor is changed by segmenting the windings and deenergizing some of the windings in each phase. These electric motors comprise an inverter that provides to convert the direct current received from a power supply to alternative current to be transmitted to the phases from the inverter ends.

In one of the state-of-the-art embodiments, the Japanese patent application no. JP5801541 the explanation is given for a brushless electric motor having auxiliary driving windings are connected in series to the driving windings, the midpoint of two windings in each phase is connected to the center tap with a relay or diode. Accordingly, when all three switches are closed, the current reaches the center tap skipping one of the windings at each phase.

In another state-of-the-art embodiment, the United States patent application no. US2001028202, a stator winding is divided into segments and the overall speed range of the electric motor can be extended by selectively connecting a power supply across one or more segments to thereby dynamically adjust the number of "active" turns of the stator winding.

In the Japanese patent application no. JP59083598, the windings are separated into segments and these segments are connected to relays. By changing the number of poles, variable speed of the electric motor is provided.

The aim of the present invention is the realization of a low cost electric motor that can operate at variable speeds.

The electric motor realized in order to attain the aim of the present invention is explicated in the attached claims. The electric motor comprises an inverter that converts the current received from a direct current power supply into alternative current and transmits to the phases through the inverter ends, at least two phases forming its phases that extend from its own inverter ends to a common star point and at least two windings at each phase. This type of connection of the phases is called a star-type connection. In the electric motor of the present invention, in all the phases except one, relays are situated at the midpoints of the two windings. The by-pass lines connected to the relays are connected to a secondary tap between the two windings in the last phase. In this circuit, the current that flows through the star point when the relays are in their position of connecting the two windings in each phase, skips this star point and flows through the connection point when the relays are closed from the outer windings towards the by-pass lines. In other words, in the second position of the relay, the inner windings- near the star point- are skipped, the current received from the phases flows through the connection point. Thus, the connection point serves as a secondary star point. Accordingly, the electric motor that operates at a low speed when the relays are in the position of connecting the two windings in each phase, can operate at a higher speed when the relays connect the outer windings to the by-pass lines.

[0009] By way of the present invention, an n phased electric motor can be controlled by an n-1 relay. For example, in a three-phase electric motor, using only two relays is sufficient. The electric motor of the present invention presents a considerable advantage in terms of unit costs and labor.

[0010] The electric motor realized in order to attain the aim of the present invention is illustrated in the attached figures, where:

[0011] Figure 1 - is the schematic view of an electric motor.

[0012] Figure 2 - is the schematic view of the stator winding connection when all the windings are fed in a three phased embodiment of the present invention.

[0013] Figure 3 - is the schematic view of the stator winding connection when some of the windings are fed in a three phased embodiment of the present invention.

[0014] Figure 4 - is the schematic view of the stator winding connection in a five phased embodiment of the present invention.

[0015] Figure 5 - is the schematic view of the stator winding connection in a two phased embodiment of the present invention.

[0016] Figure 6 - is the schematic view of the stator winding connection in an embodiment of the present invention comprising more than two windings in one phase.

[0017] Elements shown in figures are numbered as follows: 1. Electric motor 2. Stator

3. Rotor

4. Winding

5. Reky

6. By-pass line

7. Phase

[0018] The electric motor (1) comprises an inverter (not shown in figures) that converts the direct current received from a direct current power supply (not shown in figures) into alternative current, at least two phases (7) with a star type connection, that extend between the inverter ends (E) and a common star point (X), a stator (2) having at least two windings (4) connected to each other in series on each phase (7) and a rotor (3) that rotates in proportion to the frequency of the feed current in the windings (4) (Figure 1).

[0019] The electric motor (1) furthermore comprises at least one relay (5) each of which is empkced between two windings (4) in all the phases (7) except one phase (7), that provides to activate a different segment of the windings (4) at each position and at least one by-pass line (6) each of which connects these relays (5) to a connection point (Y) situated between the two windings (4) of the last phase (7) (Figure 2, Figure 3, Figure 4 and Figure 5). When the relay (5) is at the first position of connecting the two windings (4) on each phase (7), the current delivered from the inverter ends (E) flows through both of the two windings (4) on these phases (7), reaches the start point (X) and from here flows to the last phase (7) and returns back to the inverter. However, when the relays (5) are in the second position, the current delivered from the inverter ends (E) to the phases (7) only flow through the windings (4) between the inverter ends (E) and the relays (5) and reaches the connection point (Y). The current flowing from the connection point (Y) reaches the inverter point (E) by passing through the winding (4) of this phase (7) between the connection point (Y) and the inverter end (E). Consequently, at the second position of the relays (5), it is possible to attain a higher speed by passing the current from only a portion of the windings (4).

[0020] In a three-phase (7) embodiment of the electric motor (1) of the present invention, the stator (2) comprises three phases (7) connected to a star point (X) and double windings (4) at each phase (7) (Figure 2 and Figure 3). The electric motor (1) in this embodiment is used particularly in washing machines. In this case, only the windings (4) between the inverter ends (E) and the relays (5) are used in the spinning step requiring higher speed, and all the windings (4) are used together in the washing step requiring a lower speed. There are two relays (5), each provided between the two windings (4) of the first two phases (7). Two by-pass lines (6) connecting these relays (5) are connected to the connection point (Y) situated at the center of the two windings (4) in the third phase (7). The current (Al) delivered to the two inverter ends (E) flows through the star point (X) and activates both of the two windings (4) together at the first position of the relays (5) (Figure 2). When the relays (5) are in the second position, the current (A2) delivered to the inverter ends (E) flows only through the connection point (Y) without going to the star point (X), thus only the windings (4) between the inverter ends (E) and the relays (5) are activated (Figure 3). The more or lesser phased (7) embodiments of the electric motor (1) of the present invention, operates with the same principle (Figure 4 and Figure 5).

[0021] In an embodiment, the electric motor (1) of the present invention comprises more than two windings (4) separated from each other by relays (5) at each phase (7) (Figure 6). Accordingly the electric motor (1) can run at more than two variable speeds.

[0022] The electric motor (1) of the present invention is preferably a brushless direct current electric motor.

[0023] By way of the present invention, the speed of the electric motor (1) provided can be controlled by means of the phases (7) connected to the connection point (Y) serving as a secondary star point.

Claims

[0001] An electric motor (1) comprising an inverter that converts the direct current received from a direct current power supply into alternative current, at least two phases (7) with a star type connection, that extend between the inverter ends (E) and a common star point (X), a stator (2) having at least two windings (4) connected to each other in series on each phase (7) and a rotor (3) that rotates in proportion to the frequency of the feed current in the windings (4), and characterized by at least one relay (5) each of which is emplaced between the two windings (4) in all the phases (7) except one phase (7), that provides to activate a different segment of the windings (4) at each position and at least one by-pass line (6) each of which connects these relays (5) to a connection point (Y) situated between the two windings (4) of the last phase (7).

[0002] An electric motor (1) as in Claim 1, characterized by a relay (5) that connects the two windings (4) on each phase (7) at one position, and provides the current delivered to all the phases (7) except one to flow through the star point (X) and return back from the last phase (7) and activate all of the windings (4).

[0003] An electric motor (1) as in Claim 1 or 2, characterized by a relay (5) that in one position connects the by-pass lines (6) to the windings (4) between the inverter ends (E) and the relays (5) and provides the current delivered from the inverter ends (E) to all the phases (7) except one to flow through last phase (7) by skipping the star point (X) and activate only between the windings (4) between the inverter ends (E) and the relays (5).

[0004] An electric motor (1) as in any one of the above claims, comprising more than two windings (4) at each phase (7) separated from each other by relays (5).

[0005] An electric motor (1) as in any one of the above claims, used in a washing machine, characterized by a relay (5) that provides to attain the high speed required for spin drying in its first position, and the low speed required for washing in its second position.

[0006] An electric motor (1) as in any one of the above claims, which is a brushless direct current type.