JP7572979B2 - Capacitor-run type power supply for electric motors - Google Patents

Description

The present invention relates to a power supply device for a capacitor-run type electric motor.

In recent years, there has been an increasing demand for systems that simultaneously power multiple capacitor-run motors that operate on single-phase AC in industrial plants, and high reliability is required for operating the systems.

Figure 2 shows an example of the configuration of a capacitor-run type motor power supply device that is generally used in such cases. In a conventional capacitor-run type motor power supply device, as shown in Figure 2, a single-phase transformer 12 receives a three-phase power supply 11, extracts the single-phase power supply and supplies it to a bus 13, thereby supplying a current of a phase corresponding to the bus voltage to the main windings 15a, 15b of each motor 14a, 14b, and a current with a phase lead of 90 degrees from the main windings 15a, 15b by connecting capacitors 17a, 17b of appropriate capacity in series to the auxiliary windings 16a, 16b.

On the other hand, in regard to a power supply device for a capacitor-run type motor, Patent Document 1 states that for a single capacitor-run type motor, "the power supply can also be provided as a 'Scott-connected' transformer configured to convert three-phase power to two-phase power."

Japanese Patent Application Publication No. 06-054585

In the capacitor-run motor of the configuration shown in Figure 2 above, capacitors 17a and 17b are consumables and have a shorter lifespan than other electrical appliances. Therefore, if the number of motors in operation increases, it becomes necessary to check the capacity and replace parts periodically over a short span of time, making it difficult to reduce the frequency of maintenance and improve reliability.

For this reason, it is necessary to consider a method that allows electric motors to be operated without capacitors for each individual motor.

In response to this, although Patent Document 1 proposes the use of a Scott-connected transformer, it does not anticipate the case where a single power supply device supplies power to multiple capacitor-run motors. If Patent Document 1 is applied directly to multiple motors, all of the motors would need to be stopped simultaneously in the event of a failure in a single motor or circuit.

The present invention aims to propose a power supply device for capacitor-run motors that allows the remaining healthy motors to continue operating even if a failure occurs in one of the motors or circuit when multiple capacitor-run motors are in operation.

In order to solve the above problems, the present invention provides a power supply device for a capacitor-run type motor, characterized in that the single-phase outputs of a three-phase to two-phase conversion transformer that provides two single-phase outputs that are 90 degrees out of phase with each other are connected to busbars, one of the busbars being a busbar for connecting the main winding of a capacitor-run type motor, and the other busbar being a busbar for connecting the auxiliary winding of the capacitor-run type motor.

This invention makes it possible to improve the maintainability of capacitor-run motors while protecting the motors when multiple motors are operated simultaneously.

1 is a diagram showing a schematic configuration example of a capacitor-run type electric motor power supply device according to an embodiment of the present invention; FIG. 1 is a diagram showing a schematic configuration example of a conventional capacitor-run type electric motor power supply device.

The following describes an embodiment of the present invention with reference to the drawings.

The mechanism of a capacitor-run type electric motor power supply device according to an embodiment of the present invention will be explained below with reference to the drawings. Note that in the drawings used in this specification, the same elements are given the same reference numerals, and repeated explanations of these elements may be omitted.

Figure 1 shows an example of the schematic configuration of a power supply device for a capacitor-run type electric motor according to an embodiment of the present invention. The power supply device 1 shown in Figure 1 is composed of a Scott connection transformer 2, a main winding busbar 3, and an auxiliary winding busbar 4.

Of these, the Scott connection transformer 2 is a so-called three-phase to two-phase conversion transformer, and as its output, two single-phase AC outputs with a phase difference of 90 degrees from each other are obtained. Therefore, the Scott connection transformer may be realized, for example, by a Woodbridge connection transformer or a loop delta connection transformer.

The Scott connection transformer 2 in the example of Figure 1 receives power from a three-phase power source 5 and supplies a reference voltage to the main winding busbar 3 and a voltage with a 90 degree phase lead to the auxiliary winding busbar 4. The power supply device for a capacitor-run type motor of the present invention is characterized in that the single-phase outputs of the three-phase to two-phase conversion transformer are each connected to a busbar. In addition, one of the busbars is used as the main winding busbar 3 of the capacitor-run type motor, and the other busbar is used as the auxiliary winding busbar 4 of the capacitor-run type motor.

On the other hand, looking at the capacitor-run type motors 8a and 8b, which are loads supplied with power from the power supply side, the motors 8a and 8b have a main winding 9 and an auxiliary winding 10, and are driven by single-phase alternating current with a phase difference of 90 degrees supplied from the main winding busbar 3 and the auxiliary winding busbar 4.

As shown in FIG. 1, the multiple capacitor-run motors 8a, 8b have main winding connection ends 9a, 9b, 9c, 9d connected to circuit breakers 6a, 6b, 6c, 6d of the main winding busbar 3, and auxiliary winding connection ends 10a, 10b, 10c, 10d connected to circuit breakers 7a, 7b, 7c, 7d of the auxiliary winding busbar 3.

At this time, the open/closed states of circuit breakers 6a, 6b and 7a, 7b that supply power to the same capacitor-run motor must always be synchronized, or the open/closed states of circuit breakers 6c, 6d and 7c, 7d must always be synchronized.

As shown in Fig. 1, when an electrical malfunction occurs in the motors 8a, 8b or the circuits, the circuit breakers 6a, 6b, 6c, and 6d of the main winding busbar 3 or the circuit breakers 7a, 7b, 7c, and 7d of the auxiliary winding busbar 4 open the corresponding circuit breaker to remove the fault current, and therefore the upper transformer or other motors are not stopped. Therefore, even if multiple motors 8a, 8b are connected to the power supply device 1, the soundness of each individual motor is ensured.
The configuration shown in FIG. 1 makes it possible to realize a power supply configuration that does not require a capacitor by utilizing the Scott connection transformer 2, as compared to conventional capacitor-run type motor power supply devices.

The present invention is not limited to the above-described embodiment, but includes various modifications. For example, the above-described embodiment is described in detail to clearly explain the present invention, and is not necessarily limited to those having all of the configurations described.

1: Power supply unit 2: Scott connection transformer 3: Busbar for main winding 4: Busbar for auxiliary winding 5: Three-phase power supply 6a, 6b, 6c, 6d: Circuit breakers 7a, 7b, 7c, 7d: Circuit breakers 8a, b: Capacitor-run type motor 9a, 9b, 9c, 9d: Connection end of main winding 10a, 10b, 10c, 10d: Connection end of auxiliary winding 11: Three-phase power supply 12: Single-phase transformer 13: Busbar 14a, 14b: Capacitor-run type motor 15a, 15b: Main winding 16a, 16b: Auxiliary winding 17a, 17b: Capacitor

Claims (2)

A three-phase to two-phase conversion transformer provides two single-phase outputs that are 90 degrees out of phase with each other, and the single-phase outputs are connected to buses, one of the buses being a bus for connecting a main winding of a capacitor-run type motor and the other bus being a bus for connecting a sub-winding of the capacitor-run type motor ;
A power supply device for a capacitor-run type motor, characterized in that the main winding and the secondary winding of the capacitor-run type motor are each connected to the busbar of the three-phase to two-phase conversion transformer via a circuit breaker, and the circuit breakers of the same capacitor-run type motor are opened and closed synchronously . 2. The capacitor-run type motor power supply device according to claim 1 ,
A power supply device for a capacitor-run type motor, capable of arranging a plurality of the capacitor-run type motors, each having a main winding connected to the main winding connecting busbar and a secondary winding connected to the secondary winding connecting busbar.

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