JPS6029357Y2 - Y↓−△ starting circuit with phase advance capacitor - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a Y-Δ starting circuit with a phase advance capacitor in which the connection position of the phase advance capacitor is devised so as not to interfere with the measurement of the rated current of the induction motor.

Fig. 1 shows a conventional Y-Δ starting circuit with a phase advance capacitor, in which 1 is a three-phase induction motor, and one end of the primary winding of each phase U, V, W is connected to each of the three-phase AC power supplies. Phase R, S,
It is connected to T via a circuit breaker 3 and a main switch 4.

In addition, the other ends X, Y, and Z of each phase of the primary winding are connected to the three-phase AC on the power supply side of the main switch 4 via the operating switch 5 for connecting the primary winding to Δ. It is connected to each phase R9S, T of the power supply, and a starting switch 6 for connecting this primary winding to Y is connected to the other end x, y, z of each phase of the above-mentioned secondary winding. There is.

7 is each phase capacitor? A, 7b, 7c are connected to Δ for power factor improvement phase advancing capacitors, each terminal of which is connected to each phase Rt St of the three-phase AC power supply on the motor side of the main switch 4.
Each is connected to T.

In such a conventional Y-Δ starting circuit with a phase advance capacitor, when it is desired to measure the rated current of the motor 1, three Connect a current transformer 10 of an ammeter 9 to one phase of the phase AC power supplies R, S, and T, measure the motor current after power factor correction, and convert this to find the rated current, or This was done by removing capacitor 7.

For this reason, measuring the rated current of the motor 1 was troublesome.

In order to improve this, the main switch 4 should be installed as shown in Figure 2.
is connected to the three-phase AC power supply R, S, T on the power supply side from the connection point 8 of the switching device 5 for Δ side operation, and the phase advance capacitor 7 is connected to the connection point 8 of the main switch 4 and the switching device 5 for Δ side operation. The current transformer 10 of the ammeter 9 is connected to each phase R, S, and T of a three-phase AC power supply between the connecting point 11 of the phase advance capacitor 7, for example, and the Δ side of this S phase. It is conceivable to connect to one phase S of the three-phase AC power supply between the connection point 8 of the operation switching device 5, but in this case, the main switch 4 would switch the line current, and the first This is disadvantageous because it requires a larger capacity than when switching the phase current shown in the figure.

The present invention was developed in consideration of this point, and as shown in Fig. 3, the main switch 4 is connected to a three-phase AC switch on the motor side from the connection point 8 of the Δ side operation switch 5, similar to the one shown in Fig. 1. Connect to each phase R, S, and T of the power supply, and connect the two terminals of the phase advance capacitor 7 to two phases, for example, R and T, of the three-phase AC power supply on the motor side of the main switch 4. The remaining one terminal of the phase capacitor is connected to the remaining one phase S of the three-phase AC power supply on the power supply side of the connection point 8 of the switching device 5 for Δ side operation.
, and connect an ammeter to one phase S of the three-phase AC power supply between the connection point 8 in the S phase of the Δ side operation switching device 5 and the connection point 11 of the phase advance capacitor on the power supply side. 9
The current transformer 10 is connected to the current transformer 10.

By doing this, the current of the motor 1 before power factor correction can be measured using the ammeter 9, and by simply changing the connection position of one terminal of the phase advance capacitor in the conventional circuit shown in Fig. Conventional problems can be easily solved without increasing the capacity.

[Brief explanation of drawings]

1 and 2 are drawings showing a conventional Y-Δ starting circuit with a phase advance capacitor, and FIG. 3 is a circuit diagram showing an embodiment of the present invention, where the same reference numerals indicate equivalent parts. 1; Three-phase induction motor, 3; Circuit breaker, 4; Main switch, 5;
Δ side operation switch, 6; Y side start switch, 7; phase advance capacitor, 9; ammeter, 10; current transformer.

Claims (1)

[Scope of utility model registration request] Connect one end of each phase of the primary winding of the three-phase induction motor to each phase of the three-phase AC power supply via the main switch, and connect the other end of each phase of the secondary winding to Δ. Connect to each phase of the AC power supply on the power supply side of the main switch through an operation switch for switching, and connect this primary winding to the other end of each phase of the secondary winding to Y. In the case where a starting switching device is connected, connect the two terminals of the power factor improvement phase advancing capacitor with each phase capacitor connected to Δ on the motor side of the main switch, and connect them to two phases of the three-phase AC power supply, respectively. Connect the remaining one terminal of the phase advance capacitor to the remaining one phase of the three-phase AC power supply on the power supply side of the connection point of the Δ side operation switching device, and An ammeter and a current transformer are connected to one phase of the three-phase AC power supply to measure the current of the motor between the connection point and the connection point of the phase advancing capacitor on the power supply side. A Y-Δ starting circuit with a phase advance capacitor.