Abstract: This invention aims to provide an electric rotating machine which is free from the procedure of selecting different preset neutral current values for different types of machines, and which can detect a ground fault in a phase coil of the armature winding without suffering any erroneous operation. An electric rotating machine having an armature winding including three phase coils, which has been provided to attain the object of this invention, comprises a grounding resistor connected at a neutral of the armature winding, and current measuring apparatuses furnished for at least two phase coils, wherein phase currents through the phase coils are compared with each other, and the detection of a coil ground fault is determined when harmonic components of the phase currents differ from each other.

Abstract: A brushless alternating-current generating apparatus having a brushless alternating-current generator, an alternating-current exciter coupled to the brushless alternating-current generator, and a field winding temperature measuring device for measuring a field winding temperature of the alternating-current generator. The field winding temperature measuring device has a voltage measuring device for measuring a field voltage of the brushless alternating-current generator, a current measuring device for measuring a current supplied to the alternating-current exciter, and a field winding temperature calculating unit for calculating the field winding temperature of the brushless alternating-current generator from measured signal values from these measuring devices.

Abstract: A control system for an AC excited synchronous machine for use in an electricity generator/motor system. The AC excited synchronous machine can be driven not only in a variable-speed operation based on 2-axis current control but also in a constant exciting frequency operation based on only direct-axis current component control. A phase signal is switched to drive stably the AC excited synchronoius machine in a self-excited operation or in a rotary phase modifying operation. Further, when it is desired to start pumping-up water, a synchronizing power is provided to keep constant the rotational speed of the machine at the time of establishing a desired water pressure. Because of the switching arrangement of the phase signal, the AC excited synchronous machine can be operated as an ordinary synchronous machine exhibiting ordinary synchronous characteristics, that is, self-excited operation characteristics, rotary phase modifying operation characteristics and pumping-up start characteristics.

Abstract: An AC-excited generator/motor apparatus comprising; an AC-excited generator/motor having an armature mounting thereon; an armature winding connected to an AC power system and a rotor mounting thereon; and an exciting winding excited by an AC current. An exciting device for supplying a controlled AC exciting current to the exciting winding comprises; a device for calculating a real slip frequency based on a difference between the phase of an armature voltage appearing on the armature winding and the rotational phase of the rotor; and a device for controlling the exciting current supplied to the exciting winding from the exciting means in response to a deviation of the real slip frequency from a predetermined allowable range of slip frequencies so as to restore the real slip frequency within the allowable range of slip frequencies.

Abstract: A generator/motor system comprises a generator/motor having a primary winding and a secondary winding installed on the motor rotor coupled to a prime mover/load, a main circuit interposed between a power system and the primary winding of the generator/motor, an excitation circuit including a frequency converter inserted between a part of the main circuit and the secondary winding of the generator/motor, a frequency difference detector for determining the difference between the frequency of the power system and a frequency dependent on the rotational speed of the load, and a phase-shift control device for controlling the firing phase of the frequency converter in the excitation circuit by use of a signal from the frequency difference detector as a reference signal.