JPS6159287A - Drive for control rod - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to nuclear reactor control rod drives, particularly those of the type using electric motors.

Nearly 200 control rods are installed in a power reactor, and are used to control output by changing their positions and adjust the three-dimensional power distribution.

The electric motor-driven control rod has a structure as shown in FIG.
Screw 5-2 rotated by the rotation of
It operates in accordance with the vertical movement of the nut 3 that is engaged with K.

However, what is important about a device for operating this type of control rod is that it is simple and reliable, that the position control unit is as small as about 1III, and that high-speed insertion is possible.

Numerical control (NO) is the driving machine that performs minute positioning.
One example is the step motor, which is often used in machine tools.

As is well known, step motors have features such as open-loose position control with a wide variable speed range, and the ability to hold the control rod at its current position by exciting it with direct current, but the control circuit is It has the disadvantage of being complicated and expensive.

For this reason, it is conceivable to use an induction motor with a brake, but if minute positioning is repeated frequently, brake wear becomes a problem, and there is also the problem that a single failure of the brake could cause the control rod to fall.

Furthermore, it is also conceivable to use a motor that integrates a dynamic brake such as an eddy current brake with an induction motor, and to use an electromagnetic brake only for holding the control rod. However, dynamic brakes generate braking force when the motor rotates at high speed, and due to their characteristics, it is difficult to perform minute positioning.

The present invention has been made in view of the above points, and an object of the present invention is to provide a highly reliable control rod drive device that is capable of minute positioning and uses an induction motor with a simple structure as a drive source.

A specific embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows the outline of the electric motor used in the apparatus of the present invention, where 11 is an induction motor, 12 is a step actuator, and 13 is a rotating shaft.

A major feature of the electric motor applied to the drive device of the present invention is that the induction motor and the step actuator are directly connected to the same rotating shaft as shown in FIG. 2, and the operating characteristics thereof will be explained below.

The step actuator 12 in FIG.
It has a structure as shown in the figure, and a motor having the same structure as a general variable reluctance type step motor can be used.

In FIG. 5, 51 is a stator, 52 is a rotor, and 53 is an excitation winding.

If the excitation winding m53 is now excited by a DC power source to generate a magnetic flux as shown by the arrow in FIG. 5, the torque characteristic with respect to the rotation angle of the rotating shaft 130 will be as shown in FIG. 6. In addition, the torque-speed characteristics when rotating the rotating shaft under DC excitation, as shown in Figure 7, show that the torque rapidly decreases with respect to the speed, and as the speed increases, the torque increases again. . The drive device of the present invention effectively utilizes this characteristic, and is characterized in that the torque of the step actuator at low speed is used to output positioning and holding torque.

This is directly connected to an induction motor as shown in FIG. 2, and as shown in FIG. 3, the induction motor is connected to an AC power source 30 via a bus drive control circuit 31, and the step actuator 12 is connected to a DC power source 32.

The pulse drive control circuit 31 is, for example, a circuit as shown in FIG. 4, and is a circuit that drives the induction motor in steps.

In FIG. 4, 41 to 45 are AC thyristors, which are turned on by pulses given from p1 to p5.
It turns off when the current flowing below the holding current decreases. 4
6 is a capacitor, and 47 is a thyristor control circuit.

Now, the drive device of the present invention as shown in FIG. 3 operates as follows when rotating by a minute angle.

Now, when the thyristors 41 and 43 are turned on at time t0 as shown in FIG. 8, the electric motor 11 outputs positive torque, overcomes the torque of the step actuator, and starts rotating in the positive direction. Next, when the thyristor 45 is turned on at time t1, the phase current advances through the capacitor 46, current flows, and the motor becomes equivalent to having the excitation phase order switched, and at first the brake due to reverse excitation of the induction motor is activated. Can be applied.

When the speed falls below a certain value, a braking force is applied by the torque of the step actuator shown in Figure 7, and when the torque is at the zero torque position shown in Figure 6 or load torque is applied, it is balanced with the torque. It will stop at the specified position.

The drive device of the present invention does not only act as a brake during the rotation of Tanabata like a whirlpool brake, but also acts as a wear-free brake from the deceleration process to the time of stopping, and moreover, the angle at the time of stopping is Since it is determined only by the characteristics of the step actuator, it has the feature of allowing highly accurate positioning.

In addition, when the motor is continuously rotated at high speed for rapid insertion of the control rod, thyristors 41 and 43 (for reverse rotation, 4
2.44), it is very simple as it only needs to be turned on continuously.

It should be noted that controlling the current shown in FIG. 8 to flow using the circuit shown in FIG. 4 can be easily performed using well-known circuit technology, so the details will be omitted.

Also, as a method of applying the brake of an induction motor, vJ
Instead of flowing a leading current through a capacitor as shown in Figure 4, it is possible to simply switch between the two phases.

Furthermore, it is also possible to use a step actuator with a permanent magnet in the rotor or stator, and in this case, it is also possible to omit excitation by a DC power supply, which eliminates the problem of control rods falling due to power outages. It is also possible to eliminate the control rods, which is very advantageous in cases where control rods are installed at the bottom of the reactor.

The induction motor and the step actuator do not necessarily have to have an integral structure, and their rotating shafts can also be connected by gears or the like.

[Brief explanation of the drawing]

Figure 1 is an example of a control rod drive load to which the load of the present invention is applied, Figure 2 is a schematic diagram of the drive device of the present invention, Figure 3 is its wiring diagram, and Figure 4 is a diagram of the drive unit of the present invention. Pulse drive control circuit, fifth
6 is a diagram showing an example of a step actuator, FIG. 6 is a torque-angle characteristic diagram of FIG. 5, FIG. 7 is a torque-speed characteristic diagram, and FIG. 8 is a diagram showing an example of current flowing through an induction motor. °−゛−. 1...Motor, 2...Screw, 3...Nut,
4... Connecting rod, 5... Housing, 6... Control rod, 3o... AC power supply, 31... Pulse drive control circuit, 32... DC power supply, 51... Stator, 52...
Rotor, 53... Excitation winding a, 41-45... AC thyristor, 46... Capacitor, 47... Thyristor control circuit, 11... 4 electric motor, 12... Step actuator, 13 ···Axis of rotation.

Claims (1)

[Claims] 1. A step actuator that has stator teeth and rotor teeth with different numbers of teeth and that excites all the stator teeth at the same time;
An induction motor mechanically connected to the step actuator, a conversion means for converting the rotational motion of the induction motor into linear motion, and a control rod that is inserted into and withdrawn from the reactor in response to the linear motion of the conversion means. What is claimed is: 1. A control rod drive device comprising: a control rod drive device, characterized in that all stator teeth of the step actuator are always excited.