Abstract: The present invention provides a method for starting motors by harmonics for synchronous motors, wound-rotor and cage-rotor asynchronous motors started thereby. During the starting period, according to the present invention, the connection of the stator winding is changed so as to create some very strong harmonic fields. The harmonic fields are associated with the rotor windings and are used to improve the starting performance of the motor. The three motors all have large starting torque, small starting current and can be started by direct-on-line. The wound-rotor asynchronous motor has no brushes or, slip rings on the rotor and there is no electric contact thereby increasing the reliablity of starting and running. The running efficiency is superior to the cage-rotor asynchronous motor.

Abstract: A vane type pump suitable for a hydraulic system comprises passages communicating with the underside of the vanes in the inlet quadrant with the surrounding of the drive shaft and passages communicating the underside of the vanes in the discharge quadrant with the discharge chamber, thereby the underside of the vanes can act as a set of additional little pumps while being ineffective at zero pressure. The undervane pressure in the inlet quadrant can be tested and adjusted at any time during the operation by a manometer and an auxiliary valve. The vane type pump in accordance with the present invention is adapted to various viscosities of fluid such as 1-38 cst, 50.degree. C., and it is possible to work at negative pressure without keeping the reservoir a certain relative height and without replacing the inner component. The pump works at a high volumetric efficiency and total efficiency all the time.

Abstract: The present invention relates to an automatic device for depressing low frequency oscillation of power system. It consists of an electronic circuit incorporated in the original excitation regulator of a synchronous generator. This circuit can turn the input deviation of voltage .DELTA.V into simulating state variable deviations of angular frequency .DELTA..omega., of power .DELTA.P and of power angle .DELTA..delta., and then outputs the sum of them according to the principle of optimal control. With the device of the present invention, the output capability of a remote power station may double, a whole set of measurement and feedback devices may be spared and the distortions in measurement may be avoided. The present device has further advantages of being small in size, cheap in cost, easy to establish and high in reliability.