Synchro

Abstract: A new dual stator winding induction machine drive is described in this paper. The proposed induction machine consists of a standard squirrel-cage rotor and a stator with two separate windings wound for a dissimilar number of poles. Each stator winding is fed from an independent variable-frequency variable-voltage inverter. The proposed drive offers such advantages as speed sensorless operation, better reliability, and more flexibility to manipulate the resultant torque-speed curve of the motor. In the proposed drive, zero-speed operation is achieved by independently controlling the two sets of stator currents, hence, maintaining a minimum electrical frequency independent of the mechanical speed. This feature is especially important to minimize the negative impact of the stator resistance influence at low-speed operation and it greatly simplifies the implementation of speed sensorless control schemes. The drive is well suited for either constant volts per hertz or field-oriented (FO) operation. Circulating harmonic currents, common to most dual stator machines, are eliminated by the dissimilar pole number in each stator winding.

Abstract: The rotary machine comprises a driven rotor (2) and an electric motor (4, 14) having a stator (4) and a driving rotor (14). The stator (4) is also executed as an electromagnetic bearing (4, 14) for the driving rotor (14), and the driving rotor (14) of the electric motor (4, 14) together with the driven rotor (2) of the rotary machine forms a rotor unit (2, 14), i.e. the two rotors (2, 14) form an integral rotor (2, 14). The rotary machine can for example be a rotary pump, a centrifugal pump, a centrifuge or a stirring apparatus. The rotor (2, 14) can be constructed so as to be easily removable from the stator (4).

Abstract: The anisotropy of a cage rotor is utilized to determine the angular position of the rotor in an induction machine. The switching transients generated by a pulsewidth-controlled inverter serve as test signals. The response of the three-inverter terminal currents is exploited to derive a quasi-instantaneous rotor position signal. The position is sensed at the inverter through the 3-phase motor cable by measuring the current derivatives. The method does not require additional wire connections. It is applicable to induction motors having the stator windings connected either in wye or in delta. The results are supported by measurements from an experimental setup.

Abstract: The brushless direct current motor comprises a housing 10, a stator 13 and a rotor 11 within the housing, windings on the stator, sensors for sensing the position of the rotor relative to the stator and electronic circuitry for switching the current in the windings in response to outputs from the sensors to cause the rotor to rotate relative to the stator. The sensors and at least a part of the electronic circuitry are encapsulated in an electrically insulating and fuel resistant material in a container within the housing.