JPS596484B2 - electromagnet device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnet device suitable for use in a nuclear magnetic resonance apparatus.

Since electromagnet devices used in nuclear magnetic resonance apparatuses are required to have high magnetic field strength and high stability over long periods of time, large magnet devices whose temperature is controlled by liquid cooling or gas cooling are generally used.

However, since such a large magnet device has a large heat capacity, it takes about 4 to 5 hours after the power is turned on to reach a thermal equilibrium state and reach a stable state where measurements can be made, and it can take up to 12 hours when performing particularly precise measurements. It required a long warm-up time. Therefore, in the past, electromagnet devices were operated continuously day and night, including at night when they were not in use, resulting in a huge waste of electricity and water used for cooling. The present invention has been made in view of the above-mentioned conventional problems, and it maintains the electromagnetic device at around the equilibrium temperature during operation even after the power is turned off, thereby shortening the warm-up time after the power is turned on, thereby allowing continuous day and night operation. It is an object of the present invention to provide an electromagnetic device that eliminates the need for electromagnets and can prevent waste of power and water.

The present invention will be explained in detail below using the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention, and in the figure, numeral 1 denotes an electromagnet having an excitation coil cooling pipe inside. The electromagnet 1 is connected to a cooling device 2 by a water pipe 3.
The cooling device 202 is composed of a heat exchanger, a circulation pump, a valve, etc., and supplies pure water to the electromagnet 1 using a pump, absorbs the heat generated by the electromagnet 1, and returns the purified water to the tap water. Water CW is cooled by a heat exchanger through which water is passed through a valve, and then sent to the electromagnet again. 254 is an excitation power source, 5 is an auxiliary power source, and current from each power source is sent to the electromagnet 1 via a changeover switch 6.

A control signal from a temperature controller T is supplied to the auxiliary power supply 5. The temperature controller 7 generates a control signal based on a temperature signal from a temperature sensor 8 attached to an appropriate part of the electromagnet 1 and sends it to the auxiliary power source 5.
Further, the cooling operation of the cooling device 2 is stopped in conjunction with the operation of the changeover switch 6. In the configuration as described above, when the electromagnet 1 is in operation, the 35 selector switch 6 is turned to the excitation power source 4 side, and an excitation current is supplied to the electromagnet.

The cooling device 2 circulates pure water to the electromagnet 1 through the water guide pipe 3, and P! In addition, the heat generated from the electromagnet 1 is absorbed.

Pure water, whose temperature has increased by absorbing heat, is transferred to a heat exchanger.
It is cooled by tap water and sent to the electromagnet again. Under such operating conditions, the amount of heat generated by the electromagnet and the amount of heat taken away by the pure water are in equilibrium, and the electromagnet is maintained at a constant temperature. Therefore, the magnetic field generated by the electromagnet becomes stable, and the sample is measured in this stable state. When the measurement is completed and the operation of the electromagnet 1 is stopped, the operation is performed according to the procedure shown in FIG. 2 so that the electromagnet is not overheated or overcooled.

That is, when the excitation power source 4 shown in Fig. 2a is turned off, no new heat is generated, but the heat accumulated inside the excitation coil does not disappear immediately, so if the pump of the cooling device 2 is stopped, and circulate pure water to 0F at this point.
When the temperature is set to F, this latent heat has nowhere to be taken away, so the temperature of the entire electromagnet increases, and the electromagnet is undesirably overheated, albeit temporarily. Therefore, as shown in FIGS. 2B and 2C, the excitation coil is operated for a while even after the excitation power source is turned off, and the excitation coil is cooled. Then, the auxiliary power supply 5 is turned to 0N at an appropriate timing as shown in d of the same figure, and then the pump and the tap water are turned off in that order as shown in B and C of the same figure.
be put into a state. By the way, when the auxiliary power source 5 is ON1, in other words, when the changeover switch 6 is turned to the auxiliary power source side, the preheating current is supplied to the electromagnet 1 from the auxiliary power source 5.

The preheating current is a current to maintain the electromagnet at a temperature in a thermal equilibrium state during operation or at a temperature close to the optimal temperature for heat retention, and the current value is such that no heat is taken away because the cooling device is stopped. Therefore, an excitation current value of 1 or less during operation is sufficient. At this time, temperature controller 7
The sensor 8 detects the temperature of the electromagnet 1, and if there is a difference from the optimum temperature, a control signal corresponding to the difference is sent to the auxiliary power source 5 to change the preheating current. Therefore, the electromagnet is always kept at the optimum temperature even when the operation is stopped. When restarting operation, the electromagnet can therefore reach a thermally equilibrium stable state in a very short warm-up time. As described above, according to the present invention, warm-up time can be significantly shortened, so there is no need for continuous day and night operation as in the conventional case, and waste of electric power and tap water can be prevented.

It goes without saying that when starting operation, the procedure for stopping the engine is completely reversed, as shown in Figure 2.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention.
The figure is a diagram for explaining the operation. 1: Electromagnet, 2: Cooling device, 4: Excitation power supply, 5: Auxiliary power supply, 6: Selector switch, 7: Temperature controller, 8: Temperature sensor.

Claims (1)

[Claims] 1. In an electromagnet device including an excitation coil, an excitation power source that supplies an excitation current to the coil, and a cooling device for cooling the excitation coil, an auxiliary power source is provided, and the auxiliary power source is turned on when the electromagnet device is not in operation. An electromagnet device, characterized in that the electromagnet device is configured to supply a preheating current for heating the electromagnet device to a substantially constant temperature to the excitation coil, and to stop the operation of the cooling device.