Magnetic flux detector and detection method

A magnetic flux detector comprising:

• a magnetic flux generator, which includes an exciting coil and generates a magnetic flux when an excitation current is supplied to said excitation coil;
• an excitation current controller, which controls said excitation current being supplied to said exciting coil;
• a search coil, which is placed in a magnetic path where the magnetic flux generated by said magnetic flux generator passes, such that an electromotive force is induced in said search coil in response to a change in the magnetic flux;
• and
• a magnetic flux calculator, which determines the magnitude of the magnetic flux generated by said magnetic flux generator by measuring the electromotive force induced in said search coil;
• wherein:
• said excitation current controller controls said excitation current to increase from zero to a predetermined current value during a first predetermined time period and then to decrease from the predetermined current value to zero during a second predetermined time period;
• and
• said magnetic flux calculator determines the magnitude of the magnetic flux generated by said magnetic flux generator based on a difference between an increasing electromotive force integral value which is calculated by integrating the electromotive force induced in said search coil during said first predetermined time period and a decreasing electromotive force integral value which is calculated by integrating the electromotive force induced in said search coil during said second predetermined time period.