| 摘要 |
PURPOSE:To compensate delay of an eddy current at high speed by comparing a magnetic flux simulation value obtained from a simulation circuit of an electromagnet with a practical value, setting up a feedback circuit so as to be driven similarly to the practical circuit and adding a differential value of an effective current relating to an obtained eddy current time constant to a command value to obtain an effective current command value. CONSTITUTION:Magnetic flux phi is detected by a magnetic flux detector 4, in a simulation value obtained through a simulation circuit consisting of a multiplier 51B, and an integrator 53A, a deviation (e) between the simulation value and the value phi is extracted through the adder/subtractor 54C, multiplied by the simulation value by means of a multiplier 51C and integrated by an integrator 53B and the integrated value is inputted to the multiplier 51B. At that time, the output (a) of the integrator 53B corresponds to an eddy current time constant. The input of the integrator 53 is always supervised by a comparator 56, a switch is opened/closed and the value (a) corresponding to the eddy current time constant is stored in the integrator 53B. In said constitution, a delay due to the eddy current can be compensated without executing measuring/adjusting work, a sharp pulse-like magnetic flux is obtained, and even if a coil having the temperature change of a resistor or a different time constant is used, adjustment in each change can be omitted.
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