No abstract

A mathematical model of the magnetic field in the working clearance of a magnetoelectric valve motor is presented when the rotor is misaligned relative to the stator axis, which occurs during manufacture, for example, due to defects in bearing panels or during operation due to bearing wear. Using the conformal transformation of an uneven air gap into a uniform (circular ring), a study of the magnetic field in the air gap of the engine was carried out. A case is considered when the section of the air gap with the minimum size is stationary and is associated with a specific place on the surface of the stator boring. The serrature of the stator was taken into account on average using the Carter coefficient. The magnetic field in the inhomogeneous air gap created by the rotor magnets and the current of the stator winding was assumed to be plane-parallel, having a two-dimensional character. It is obtained that the misalignment of the rotor associated with the rotational motion of the air gap section with a minimum size leads to the appearance of non-sinusoidal EMF and pulsations of electromagnetic moment with a frequency exceeding 3p times the rotational speed of the rotor (p is the number of pairs of poles). With fixed eccentricity, an alternating EMF is induced along the rotor shaft, causing alternating current in the circuit: shaft – bearings – bearing panels – stator housing. Pulsations of the moment of the electromagnetic moment of the engine are caused by the appearance of mainly the 3rd and 9th harmonics, the values of which increase with increasing misalignment according to a law close to linear. The constant component of the electromagnetic moment increases somewhat with increasing misalignment.

Relevance of study. Starting of the medium voltage synchronous machine at standstill is one of the main problems in the operation of unregulated synchronous electric drives. The optimal solution is starting the excited synchronous machine fed by the thyristor statical frequency converter. A sensorless control of the statical frequency converter for thyristor switching of load-commutated inverter to functions of synchronous machine angular rotor position in the area of zero and low speed, has not yet received a clear solution. The purpose of this study is the design of the sensorless control method for the thyristor statical frequency converter at the synchronous machine startup under conditions of angular acceleration uncertainty. Materials and methods. Methods of theory of electrical machines and computer mathematical simulation are used in the study. Results of the study. The regularity between the angular rotor position and the non-conductive phase stator voltage of the synchronous machine is determined. The rotor rotation angle of the synchronous machine is defined as the ratio of the conductive state duration of the thyristor arm pair of the load-commutated inverter to the period determined from the non-conductive phase stator voltage of the synchronous machine. The sensorless control method is based on simultaneous operation of scalar control, indirect angular rotor position determination and cross-control channels. The proposed sensorless control method is tested by computer mathematical simulation of the system «thyristor statical frequency converter –synchronous machine». Findings. The application of the considered control method was found for commercially available medium voltage thyristor frequency converters of EKRA Ltd. The considered method can be used for the sensorless control of frequency converter by different topology.

No abstract

No abstract