JPH0711932B2 - Electrical circuit turn-on / off control method - Google Patents

Description

Description: INDUSTRIAL APPLICABILITY Fields of application High voltage power supply devices using semiconductor switching devices such as solid state relays and triacs, motor power supply devices, etc., especially in power supply devices that are frequently turned on and off,
The present invention relates to a control method for making and breaking an electric circuit, which is capable of significantly reducing an increase in current capacity and power loss due to the influence of an exciting inrush current at the time of making a small size and saving energy.

Conventional technology Devices such as transformers and reactor electromagnets that use magnetic materials have a hysteresis characteristic of ferromagnetic materials.Therefore, depending on the phase when the power is turned on, an exciting current that is several times as large as that during normal use flows In order to avoid this, (a) Use two sets of switching elements, and connect a resistor in series to one set of switching elements to be closed first to limit the current value, and after a few cycles, Another set of switching elements shorts this resistor.

(B) The phase angle control is performed to gradually apply the voltage to reduce the influence of the hysteresis characteristic.

Etc. are adopted.

Problems to be Solved by the Invention In (a) above, the power loss in the resistor increases when the frequency of making and breaking is high.

In (b) above, it is not applicable when high speed operation is required due to the time delay until all the voltages are applied.
Further, the phase angle control has a drawback that the charging current becomes excessively large when the capacitor is connected to the load side, which is not suitable.

Means for Solving the Problems The present invention is intended to provide an electric circuit turn-on / off control method in which the above-mentioned drawbacks are eliminated, and a transformer using a ferromagnetic material connected to a three-phase AC power supply, This is a make / break control method for an electric circuit that includes equipment such as reactors and electromagnets, and the voltage that causes a current to flow in the opposite direction to the direction of the current at the time of breaking the electric circuit just before it rises rises from zero. It is performed within a phase range of ± 120 degrees with respect to the phase to reduce the value of the inrush current due to the magnetic saturation phenomenon.

Action A device using a ferromagnetic material has a magnetization curve as shown in Fig. 2, and when energized, it becomes A → B → A '→
The magnetization state changes periodically along the hysteresis loop of B ′ → A.

The magnetic flux φ changes in proportion to the time-integrated amount of the voltage applied to the device, and when a sinusoidal AC voltage having an effective value E1 [V] is applied, the magnetic flux change amount φa is given by the following equation.

However, f: frequency [Hz] N ₁ : E ₁ [V] is the number of linkages between the conductor and the ferromagnetic material to which a voltage is applied.

When the device is cut off from the power source, the magnetized state becomes the point B or B'on the magnetization curve. If the magnetization state at the point B is reached, assuming that the phase of the voltage to be applied next time is the phase rising in the direction of flowing the current in the + I direction, the magnetic flux φ further increases by φa from the point B and the magnetization state is increased. Becomes the point C, and the exciting current I has its peak value I ₂ . On the contrary, if the phase of the voltage to be applied next time is the phase rising in the direction of flowing the current in the −I direction, the magnetic flux φ changes from −point by −φa and the magnetized state becomes C ′. As for I, its peak value I ₁ flows. The absolute value of the exciting current I ₁ is compared to the absolute value of the exciting current I _2, it can be kept low as a fraction of.

Further, the phase of the voltage to be applied next time advances by 120 degrees with respect to the phase rising from zero in the direction of flowing the current in the -I direction,
Or even if there is a delay, the maximum change in magnetic flux is approximately 75% of the above φa, and the peak value of the exciting current is approximately the same as I ₁ above.
Limited to 70%. In this case, the square integral value of the current, which is a measure of the thermal stress of the switching element, remains at about 50% of the value when I ₁ flows.

The electrical circuit turning-on / off method according to the present invention is 180 ° opposite to the worst voltage phase shifting from the B point to the C point, which is from the B point to the C ′.
Within the range of ± 120 degrees centered on the phase of the voltage moving to the point,
The control is performed so as to perform the next closing to reduce the exciting inrush current.

Examples Examples of the present invention will be described below.

FIG. 1 shows an embodiment, 1 is an AC power supply, 2 is a high-speed switching element, 3 is a phase detection circuit, 4 is a storage circuit, 5 is an arithmetic circuit,
6 is a control command and 7 is a load.

The phase information when the cutoff signal is sent from the arithmetic circuit 5 to the high-speed switching element 2 in accordance with the cutoff command of the control command 6 is held in the storage circuit 4, and the phase detection circuit 3 receives the next command to input the control command 6 from the phase detection circuit 3. The power supply phase information and the previous cutoff phase information of the memory circuit 4 are compared and calculated by the arithmetic circuit 5, and when a proper closing phase is reached, a closing signal is sent from the arithmetic circuit 5 to the high speed switching element 2 and the load 7 is switched to the AC power source 1 Throw in. The input phase information at this time is held in the storage circuit 4.

In response to the cutoff command, the control command 6 thereafter sends a cutoff signal from the arithmetic circuit 5 to the high-speed switching element 2 to cut off the load 7 from the AC power supply 1. At this time, the cutoff phase information is stored in the memory circuit 4
Held in. In this manner, the load 7 is switched on and off alternately.

When the demand for high-speed responsiveness is low, the method of omitting the memory circuit shown in FIG. 1 and fixing the closing phase and the closing phase within an appropriate range is also the closing / closing control method of the electric circuit of the present invention. It is included.

Further, the electric circuit closing / closing control method of the present invention can be realized as a module in which the phase detection circuit 3, the arithmetic circuit 5, the high-speed switching element 2 and the like are integrated.

Effects of the Invention As described above, in the electric circuit closing / closing control method according to the present invention, the closing of the electric circuit including the ferromagnetic device connected to the AC power supply means the direction of the current at the time of breaking just before the closing. ± 12 with respect to the phase where the voltage that flows the reverse current rises from zero
The current capacity on the power supply side can be reduced by reducing the excitation inrush current due to magnetic saturation, that is, by preventing the excitation inrush phenomenon, by reducing the current capacity on the power supply side. It has remarkable effects such as reduction of power loss due to inrush current, and has great industrial and practical value.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an electric circuit closing / closing control system of the present invention. FIG. 2 is a magnetic flux-exciting current characteristic diagram of a ferromagnetic device for explaining the principle of the present invention. 1: AC power supply, 2: High-speed switching element 3: Phase detection circuit, 4: Memory circuit 5: Arithmetic circuit, 6: Control command, 7: Load

Claims (1)

[Claims] 1. In a closing / closing control system of an electric circuit including a transformer / reactor, an electromagnet, and the like, which uses a ferromagnetic material connected to a three-phase AC power supply, the electric circuit is closed immediately before the closing. An electric circuit closing / closing control method characterized in that it is performed within a phase range of ± 120 degrees with respect to the phase in which the voltage that causes the current to flow in the direction opposite to that at the time of breaking is raised from zero.