JPH0832161B2 - Electromagnet power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an electromagnet power supply used for an accelerator electromagnet or the like for accelerating electrons or protons to high energy.

(Prior Art) Accelerators for accelerating electrons or protons to high energy have come to be used for obtaining synchrotron radiation as a light source for microfabrication of VLSI and for studying particle physics. . The accelerator controls the output current of a constant current power source connected to each electromagnet coil to generate a desired magnetic field and control the orbits of electrons or protons. The electromagnet power source used in such an accelerator is required to be controlled with high accuracy over a wide range of current values. For example, there are systems that require an accuracy of ± 1 × 10 ⁻⁴ within the rated range of 2% to 100%. One of the circuits satisfying such requirements is shown in FIG.

In FIG. 2, 1 is an AC bus, 2 is a rectifier transformer, 3 is a rectifier composed of a diode or a thyristor for converting an AC into a desired DC, 4 is a reactor, 5 is a capacitor, 6 is DC of the rectifier 3. A chopper circuit that turns the output voltage on and off at high speed and controls the load current at high speed and accuracy.
7 is a diode that circulates a load current when the chopper circuit 6 is off, 8 is an electromagnet coil that is a load, 9 is a DC current detector that detects the coil current, 10 is a coil current reference setting device, and 11 is a reference setting device. A constant current control circuit for inputting the difference between the output of 10 and the coil current detected by the DC current detector 9 and controlling so that the difference becomes 0, 12 is a control signal from the constant current control circuit 11. A pulse width modulation circuit that determines the current-carrying width of the chopper 6 in accordance therewith, and a driver circuit 13 that drives the chopper based on an on / off command of the pulse width modulation circuit 12.

The circuit shown in FIG. 2 operates as follows. First, the rectifier 3 is operated. When the DC voltage is sufficiently established, the constant current control system is operated, and high-speed current control is performed by the pulse width control of the chopper. The output voltage of the rectifier 3 is determined by the constant of the load coil and the required current value and current rising speed, and the frequency of the pulse width control of the chopper is determined by the time constant of the load coil and the required accuracy.

(Problems to be Solved by the Invention) One of the operation modes of the accelerator is an operation in which the electromagnet current is rapidly raised and lowered at a short cycle. For example 0.9
There is an operation mode in which the current is raised from 0% to 75% of the rated value in seconds and then repeated every 2 seconds. So 75% to 0%
It is necessary to lower the current within 1.1 seconds. But,
Since the circuit shown in FIG. 2 cannot supply a negative voltage, the chopper 6 is turned off and the load coil 8,
There is no choice but to circulate the current through the diode 7 and attenuate it with the load time constant. If the time constant of the load is small, the current can be reduced from 75% to 0% within 1.1 seconds by this method, but if the time constant of the load is large, the current cannot be reduced within 1.1 seconds, and the cycle is 2 seconds. There was a problem that it became impossible to drive. For example, rated current 350A, load coil constant 200m
In the case of H and 100mΩ, the current after 1.1 seconds will decrease when the current is 2.5% which is 75% of the rated value and is attenuated by the time constant of the load. It has only dropped to 106 (A). However, in the above equation, I ₀ is the initial current.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electromagnet power supply device capable of repeating the operation in a short cycle by speeding the fall of the current without providing a means for supplying a negative voltage.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a switch 16 between a chopper 6 and a load coil 8 as shown in FIG. Resistor 14 and diode in parallel with coil 8
It is provided with 15 series circuits.

(Operation) The present invention is configured as described above. When the current is lowered, the switch 16 is turned off, so that the load current circulates through the diode 15 through the resistor 14. Therefore, the discharge time constant Can be reduced to a desired value by appropriately selecting the resistance value of the resistor 14, so that
It becomes possible to perform the operation of raising and lowering the current in a short cycle.

(Example) An example of the present invention is shown in FIG. In FIG. 1, the same elements as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.
14 is a resistor for attenuating the load current when the current falls, 15 is a diode for preventing current from flowing to the resistor 14 side during steady operation, 16 is off when the current falls, and the load current is A switch for commutating to the device 14 and the diode 15 side, and 51 is a current fall command for turning off the switch 16 and blocking the chopper 6.

 Next, the operation of the present invention will be described with reference to FIG.

The rectifier 3 is operated in advance to establish the necessary current and voltage. The switch 16 is turned on by the current rising command, the chopper 6 is operated, and the current is started according to the current reference 10.
When the current reaches a predetermined value, the chopper 6 is stopped by the current falling command, the switch 16 is turned off, and the load current is circulated through the diode 15 and the resistor 14. Load current is resistor
The presence of 14 quickly reduces it. For example, if the rated current is 350 A, the coil constant is 200 mH, and 100 mΩ as described above, and if the resistance value of the 14 resistors is 1 Ω, the current value of 262.5 A, which is 75% of the rated value, will be 1.1 seconds later. It has decreased to 0.6 (A). However, in the above formula, I ₀ is the initial current, R is the constant of the load resistance and resistance 14, and L
Is the load inductance.

The constant of the resistor 14 is optimally determined by the load constant, the fall time and the current value.

[Effects of the Invention] As described above, according to the present invention, in an electromagnet power supply device including a rectifier for converting an AC voltage into a DC voltage and a chopper for turning on / off the DC voltage, a switch is provided in series on the load side of the chopper, By providing a reverse polarity diode and a resistor in parallel, the load current can be lowered at a desired time, and an electromagnet power supply device that can also support an operation mode in which the rise and fall of the current are repeated in a short cycle is provided. Can be provided.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, and FIG. 2 is a circuit configuration diagram showing a conventional electromagnet power supply device. 1 ... AC bus, 2 ... Transformer for rectifier, 3 ... Control rectifier,
4 ... Reactor, 5 ... Capacitor, 6 ... Chopper circuit,
7 ... Diode, 8 ... Load coil, 9 ... DC current detector, 10 ... Current reference setting device, 11 ... Constant current control circuit, 12 ... Pulse width modulation circuit, 13 ... Driver circuit, 14 ... Resistor, 15 ... Diode, 16 ... Switch, 51 ... Current lowering signal.

Claims (1)

[Claims] 1. A rectifier for converting an AC voltage into a DC voltage,
An electromagnet power supply device comprising a chopper circuit composed of a first switching element and a first diode connected in parallel to the rectifier, and an electromagnet coil connected in parallel to the first diode, wherein an output side of the chipper circuit is provided. A second switching element that is provided and is turned off by the electromagnet current fall command signal, and a resistor that is connected in parallel to the electromagnet coil for causing the electromagnet coil current to flow back when the second switching element is turned off. An electromagnet power supply device comprising a series circuit including a second diode and a second diode.