GB2151092A

GB2151092A - Single-phase asynchronous electric motor

Info

Publication number: GB2151092A
Application number: GB08429001A
Authority: GB
Inventors: Niels Due Jensen
Original assignee: Grundfos AS
Current assignee: Grundfos AS
Priority date: 1983-11-23
Filing date: 1984-11-16
Publication date: 1985-07-10
Also published as: FR2555376A1; SE459300B; IT8423668A1; DK536583D0; DK536583A; SE8405764D0; SE8405764L; JPS60134795A; DE3440923A1; NL8403546A; IT1177269B; GB8429001D0; IT8423668A0

Abstract

The motor has main windings A'1, A'2 connected in series across the supply, a series circuit of a capacitor C' and an auxiliary winding S, and a switch 1' by means of which the capacitor C' and auxiliary winding S are connected either in parallel with both windings A'1, A'2 to provide a high torque during starting, or in parallel with only the winding A'2 during normal running. <IMAGE>

Description

SPECIFICATION Single-phase asynchronous electric motor This invention relates to a single-phase asynchronous electric motor.

According to the invention there is provided a single-base asynchronous electric motor having a plurality of main windings, an auxiliary winding connected in parallel with one or more of the main windings, and a capacitor connected in series with the auxiliary winding.

This invention will now be described by way of example with reference to the drawing, in which: Figure 1 illustrates a known single-phase asynchronous electric motor; Figure 2 illustrates a single-phase asynchronous electric motor according to the invention; and Figure 3 is a graph illustrating torque as a function of motor speed for the start-up phase and running phase conditions of the motor of Fig. 2.

The motor illustrated in Fig. 1 is a singlephase asynchronous electric motor having main windings A1 and A2, a capacitor C connected in series therewith, and an auxiliary winding S which by means of a switch 1 can be connected in parallel with one or more of the main windings and capacitor. With this arrangement the switch 1 is set, as shown, to connect the auxiliary winding S in parallel with both main windings At and A2 and the capacitor C during a start-up phase of operation of the motor to provide a relatively high torque. Once the motor is running at the required speed the switch 1 is operated such that the auxiliary winding S is then connected in series with one or both of the main windings A1 and A2 A disadvantage of such an arrangement is that the capacitor is used only as a runningphase capacitor, and is at all times subjected to the full voltage.

The motor illustrated in Fig. 2 is a singlephase asynchronous electric motor having main windings A1, and A2,, an auxiliary winding S' having a capacitor C' connected in series therewith, and a switch 1' by which the series arrangement of auxiliary winding S and capacitor C' can be connected in parallel with either one or both of the main windings A' and A'2.

In this manner the capacitor is utilized both as a starting-phase capacitor and as a running-phase capacitor, whereby a high ratio of starting moment to running moment is obtained. For starting the switch 1' is placed in the position not shown in Fig. 2, and when the motor is running the switch 1' is switched to the position shown in Fig. 2.

Fig. 3 shows plots of the moment D as a function of the number n of revolutions of the motor in the starting-phase and the runningphase conditions.

An advantage of the motor according to the invention is that transients are avoided during operation of the switch and at the same time the voltage across the auxiliary winding and the capacitor is reduced when the motor is in the running condition, which ensures a reduced loss.

1. A single-phase asynchronous electric motor having a plurality of main windings, an auxiliary winding connected in parallel with one or more of the main windings, and a capacitor connected in series with the auxiliary winding.

2. A motor as claimed in claim 1, in which the series arrangement of the auxiliary winding and the capacitor is connected in parallel with all the main windings during a start-up phase of operation of the motor.

3. A motor as claimed in claim 1 or claim 2, in which the series arrangement of the auxiliary winding and the capacitor is connected in parallel with at least one but not all of the main windings during a running phase of operation of the motor.

4. A motor as claimed in claim 2 or claim 3, including a switch by which the connection of said series arrangement can be changed.

5. A single-phase asynchronous electric motor having two series connected main windings; a series arrangement of an auxiliary winding and a capacitor; and a switch by which said series arrangement can be connected in parallel with both main windings during a start-up phase of operation of the motor, and can be connected in parallel with only one of the main windings during a running phase of operation of the motor.

6. A single-phase asynchronous electric motor, substantially as hereinbefore described with reference to Fig. 2 of the drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Single-phase asynchronous electric motor This invention relates to a single-phase asynchronous electric motor. According to the invention there is provided a single-base asynchronous electric motor having a plurality of main windings, an auxiliary winding connected in parallel with one or more of the main windings, and a capacitor connected in series with the auxiliary winding. This invention will now be described by way of example with reference to the drawing, in which: Figure 1 illustrates a known single-phase asynchronous electric motor; Figure 2 illustrates a single-phase asynchronous electric motor according to the invention; and Figure 3 is a graph illustrating torque as a function of motor speed for the start-up phase and running phase conditions of the motor of Fig. 2. The motor illustrated in Fig. 1 is a singlephase asynchronous electric motor having main windings A1 and A2, a capacitor C connected in series therewith, and an auxiliary winding S which by means of a switch 1 can be connected in parallel with one or more of the main windings and capacitor. With this arrangement the switch 1 is set, as shown, to connect the auxiliary winding S in parallel with both main windings At and A2 and the capacitor C during a start-up phase of operation of the motor to provide a relatively high torque. Once the motor is running at the required speed the switch 1 is operated such that the auxiliary winding S is then connected in series with one or both of the main windings A1 and A2 A disadvantage of such an arrangement is that the capacitor is used only as a runningphase capacitor, and is at all times subjected to the full voltage. The motor illustrated in Fig. 2 is a singlephase asynchronous electric motor having main windings A1, and A2,, an auxiliary winding S' having a capacitor C' connected in series therewith, and a switch 1' by which the series arrangement of auxiliary winding S and capacitor C' can be connected in parallel with either one or both of the main windings A' and A'2. In this manner the capacitor is utilized both as a starting-phase capacitor and as a running-phase capacitor, whereby a high ratio of starting moment to running moment is obtained. For starting the switch 1' is placed in the position not shown in Fig. 2, and when the motor is running the switch 1' is switched to the position shown in Fig. 2. Fig. 3 shows plots of the moment D as a function of the number n of revolutions of the motor in the starting-phase and the runningphase conditions. An advantage of the motor according to the invention is that transients are avoided during operation of the switch and at the same time the voltage across the auxiliary winding and the capacitor is reduced when the motor is in the running condition, which ensures a reduced loss. CLAIMS