JPH0311706A - Power source for superconducting coil - Google Patents

Abstract

PURPOSE:To make it possible to stop operation without quenching a coil when power is off by a method wherein a circuit, in which an auxiliary resistor, having the resistance value sufficiently smaller than protective resistance, and a closing device are series-connected, and a quenching protective resistor are parallel-connected. CONSTITUTION:After an alternate input has been AC-DC inverted through a converter 5, and also the alternate input has been contact-connected by a series transistor circuit 4, a coil 1 is excited. On the other hand, a circuit breaker 3 is turned OFF when the coil 1 is quenched, and coil energy is discharged by a quench-protecting resistor 2. On the other hand, a closing device 7 is continuously in OFF position, the flowing-in of coil exciting current is prevented, but it is turned ON simultaneously with power off, the series transistor circuit 4 is cut off, and most of the coil current is discharged by an auxiliary resistor 6. The resistance value of the resistor 6 is brought to a small value at which the coil 1 is not quenched by the generated heat by the change of magnetic flux when the auxiliary resistor discharges.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a technology for suppressing quenching of a superconducting coil (hereinafter referred to as a coil) when a power outage occurs during operation of the superconducting coil.

(Prior Art) A coil excitation power source generally has a circuit configuration as shown in FIG. “Applied Superconductivity” edited by Hiroyasu Ogiwara 2 Nikkan Kogyo Shimbun, 1986, pH 9). In other words, the coil power source is a converter using a diode or thyristor5. It consists of a series transistor circuit 4 for further constant current control of the output current from the converter 5, a breaker 3 and a quench protection resistor 2 for extracting coil energy to the outside when the coil 1 is quenched and ensuring the safety of the coil. Ru.

In such a superconducting coil power supply, in the event of a power outage, if the converter 5 is a thyristor circuit, it is possible to put it in a bypass pair and circulate the coil current, but since current control cannot be performed at all, safety is generally prioritized. , a method has been adopted in which the breaker 3 is opened and the coil energy is discharged to the quench protection resistor 2 6 In this case, the quench protection resistor 2 is installed for the purpose of suppressing the coil temperature rise when the coil 1 is quenched. Therefore, its resistance value is relatively large, and therefore, coil 1 is rapidly discharged6.Therefore, there is a high possibility that coil 1 will be quenched by the eddy current due to the sudden change in magnetic flux within coil 1. This is a serious problem when the coil is operated in the summer or in rural areas where the probability of occurrence is high.

(HM to be Solved by the Invention) An object of the present invention is to provide a coil power source that safely discharges the coil without causing quenching during a power outage.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention has a resistance value that is small enough that the coil does not cause quenching even if discharged at the discharge rate, in addition to the quench protection resistor.

Connecting the auxiliary resistor in parallel with the quench protection resistor 6 (Function) By doing this, most of the coil energy will be discharged through the auxiliary resistor when a power outage occurs.

In such a discharge, the rate of change of the magnetic flux within the coil is slow, so there is little alternating current loss generated within the coil, and the coil can be stopped without being quenched due to the heat generated.

(Example) The present invention will be described below with reference to an example shown in the drawings.

FIG. 1 shows the main circuit of a coil power supply according to the invention.

After the AC input is converted into AC/DC through the converter 5, it is further subjected to constant current control by the series transistor circuit 4, and then the coil 1 is excited. On the other hand, when the coil 1 is quenched, the breaker 3 is opened and the coil energy is discharged through the quench protection resistor 2.

On the other hand, the input device 7 is normally open to prevent the inflow of coil excitation current, but is closed upon power outage, and the series transistor circuit 4 is cut off to discharge most of the coil current through the auxiliary resistor 6.

The resistance value of the auxiliary resistor 6 is set to a value small enough to prevent the coil 1 from being quenched due to the heat generated by the change in magnetic flux during this discharge. Further, when the converter 5 is composed of a thyristor, instead of cutting off the series transistor circuit 4, its gate shift block operation can be used instead. Further, in the event that the coil 1 is quenched during discharging by the auxiliary resistor 6, a normal quench protection circuit can be formed by opening the breaker 3 to ensure the safety of the coil 1.

In this way, in the event of a power outage, most of the coil energy is gently discharged through the auxiliary resistor 6, so that the coil 1 can be stopped without being quenched.

(Other Embodiments) FIG. 3 is a main circuit of a coil power supply showing another embodiment of the present invention. A free wheel diode 8 is provided in place of the auxiliary resistor 6 and input device 7 shown in FIG.

Its action is similar to that shown in FIG. In addition, freewheeling diode 8
The discharge speed can be adjusted by changing the number of series. In this case, there is an advantage that the feeder 7 is not required.

〔Effect of the invention〕

According to the present invention, it is possible to stop the coil without quenching it during a power outage.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a coil power supply circuit according to a first embodiment of the present invention, Fig. 2 is a diagram showing a coil power supply circuit according to another embodiment of the present invention, and Fig. 3 is a diagram showing the main coil power supply circuit of a conventional coil power supply. It is a diagram showing a circuit.

Claims (2)

[Claims] (1) A circuit in which an auxiliary resistor with a resistance value sufficiently smaller than the protective resistor and a dosing device are connected in series is connected in parallel with the protective resistor,
A superconducting coil power source characterized in that, in the event of a power outage, the magnetic energy of the superconducting coil is discharged through an auxiliary resistor by gate operation of a converter or cut-off operation of a series transistor circuit. (2) A freewheeling diode is connected in parallel with a protective resistor, and in the event of a power outage, the magnetic energy of the superconducting coil is gradually consumed by the freewheeling diode by gate operation of the converter or cutoff operation of the series transistor circuit. Superconducting coil power supply.