A system for a first digitally controlled grounded inductor simulation circuit may include an OP-AMP, a digitally controlled current amplifier (DCCA), a voltage buffer, two resistors, and a capacitor. The first digitally controlled grounded inductor simulation circuit allows adjustment of an equivalent inductance value (CR.sub.1R.sub.2/A) through programming a digitally controlled current gain (A) of the DCCA. A system for a second digitally controlled grounded inductor simulation circuit includes an OP-AMP, a digitally controlled current amplifier (DCCA), a dual output current follower (CF), an active current division network (CDN), two resistors, and a capacitor. The second digitally controlled grounded inductor simulation circuit allows adjustment of an equivalent inductance value (CR.sub.1R.sub.2/αA) via programming the active CDN and the DCCA.

A system and method for detecting the location of coil open and coil short faults. The method includes obtaining an instantaneous admittance signature of each solenoid coil, sending out a periodic test signal to each valve, obtaining a new admittance signature; and calculating the coil-open and coil-short faults.

A system and method for detecting the location of coil open and coil short faults. The method includes obtaining an instantaneous admittance signature of each solenoid coil, sending out a periodic test signal to each valve, obtaining a new admittance signature; and calculating the coil-open and coil-short faults.

To provide an abnormality detection apparatus for resolver which can determine the abnormality of at least the first system, even if the period of the excitation AC voltage of the first system and the period of the excitation AC voltage of the second system are different periods, and the magnetic interference between systems occurs. An abnormality detection apparatus for resolver applies an AC voltage of a first period to a first system excitation winding; applies an AC voltage of a second period different from the first period to a second system excitation winding; calculates a first system square sum which is a sum of square values of the detection values of output signals of first system two output windings after the second period component reduction processing: and determines abnormality of first system based on whether or not the first system square sum is within a normal range of first system.

To provide an abnormality detection apparatus for resolver which can determine the abnormality of at least the first system, even if the period of the excitation AC voltage of the first system and the period of the excitation AC voltage of the second system are different periods, and the magnetic interference between systems occurs. An abnormality detection apparatus for resolver applies an AC voltage of a first period to a first system excitation winding; applies an AC voltage of a second period different from the first period to a second system excitation winding; calculates a first system square sum which is a sum of square values of the detection values of output signals of first system two output windings after the second period component reduction processing: and determines abnormality of first system based on whether or not the first system square sum is within a normal range of first system.

A transformer fault detection, where the transformer includes a primary winding coupled to a medium voltage power line and a secondary winding providing a stepped down voltage of the medium voltage. The detection system includes a switching device, where the switching device includes a first voltage measuring device for measuring the voltage on the primary winding, a controller for processing measured voltages and a transceiver for receiving and transmitting messages. The detection system also includes a second voltage measuring device for measuring the stepped down voltage on the secondary winding, where the second voltage measuring device includes a transmitter for transmitting the measured step down voltage to the switching device. The controller uses the measured voltages to calculate a transformer turns ratio (TTR) of the transformer to determine whether a transformer fault.

Provided are embodiments for determining solenoid plunger position by performing a method which includes generating, by a first signal circuit, a first signal based at least in part on a pull-in current value of a current applied to a solenoid coil of a solenoid. The method further includes generating, by a second signal circuit, a second signal by applying a time delay to the first signal. The method further includes comparing, by a comparator circuit, the first signal and the second signal to determine whether a plunger of the solenoid has moved within the solenoid from a first position to a second position. The method further includes, responsive to determining that the plunger of the solenoid has moved within the solenoid from the first position to the second position, reducing the current applied to the solenoid coil of the solenoid from the pull-in current value to a hold current value.

Provided are embodiments for determining solenoid plunger position by performing a method which includes generating, by a first signal circuit, a first signal based at least in part on a pull-in current value of a current applied to a solenoid coil of a solenoid. The method further includes generating, by a second signal circuit, a second signal by applying a time delay to the first signal. The method further includes comparing, by a comparator circuit, the first signal and the second signal to determine whether a plunger of the solenoid has moved within the solenoid from a first position to a second position. The method further includes, responsive to determining that the plunger of the solenoid has moved within the solenoid from the first position to the second position, reducing the current applied to the solenoid coil of the solenoid from the pull-in current value to a hold current value.

The characteristics of a winding to be tested is allowed to be analyzed more easily and in a shorter time. A testing instrument 1 includes an impulse voltage application capacitor Cs having one end connected to an external terminal T2, a switch SW and a current limiting resistor Rs connected in series between another end of the impulse voltage application capacitor Cs and an external terminal T1, and a parameter calculator 5. The parameter calculator 5 calculates at least one of the value of the equivalent capacitor Cd, the value of the equivalent inductor Ld and the value of the equivalent resistor Rd by performing regression analysis using a measured value of a voltage Vcd in an analysis time period Ta from turning on of the switch SW to start of resonance based on the equivalent inductor Ld, the equivalent capacitor Cd and the equivalent resistor Rd pertaining to a winding 11.

The characteristics of a winding to be tested is allowed to be analyzed more easily and in a shorter time. A testing instrument 1 includes an impulse voltage application capacitor Cs having one end connected to an external terminal T2, a switch SW and a current limiting resistor Rs connected in series between another end of the impulse voltage application capacitor Cs and an external terminal T1, and a parameter calculator 5. The parameter calculator 5 calculates at least one of the value of the equivalent capacitor Cd, the value of the equivalent inductor Ld and the value of the equivalent resistor Rd by performing regression analysis using a measured value of a voltage Vcd in an analysis time period Ta from turning on of the switch SW to start of resonance based on the equivalent inductor Ld, the equivalent capacitor Cd and the equivalent resistor Rd pertaining to a winding 11.