|
Control method of frequency-assisted electric drive According to control method of frequency-boosted electric drive in closed positions of commutators (1, 5) and disconnected commutator (7) as per signals of controller (9) there performed is engine acceleration to the frequency close to frequency of network 8. During acceleration, converter gradually increases output frequency starting from zero one. Upon completion of acceleration process of motor 6, converter 2, as a rule, is synchronised with network 6. After that, controller 9 supplies command for closure of network switch 7 and pickup of control pulses (locking) by inverter (4). When this command is being implemented, almost immediate locking of converter takes place and contacts (7) are closed just in a few milliseconds. On the motor side, converter with closed transistors represents a diode bridge, to the poles of which a capacitor is connected. Therefore, it serves as a damping chain at connection of contacts (7). Such a chain reduces possible overvoltages and vibrations occurring at connection due to non-homogeneity of closure of contacts, their rebound, disturbance of phase synchronism at synchronisation, etc. |
|
According to the first version, the thyristor device for smooth start of a HV synchronous electric motor by the underfrequency relay contains a dependent frequency converter consisting of a thyristor rectifier, a thyristor inverter, a smoothing choke, a transistor inverter, a transistor inverter with a control unit and a filter capacitor at the outputs, a voltage stabiliser paralleled to the filter capacitor, commutation apparatus connecting the corresponding input and output clamps of the thyristor and the transistor inverter by means of power contacts. According to the second version, the device contains all the elements as per the first version and, additionally, a unit setting the intensity of connection with the transistor inverter control unit and the voltage controller. |
|
In method of AC motor soft start, the motor is connected to a frequency converter, frequency start of the electric motor is carried out until the previously specified value of the frequency converter output voltage, which is less than the rated value of the electric motor supply frequency, afterwards the electric motor is disconnected from the specified frequency converter and is connected directly to the power supply network. |
|
Frequency-adjusted electric drive In frequency-adjusted electric drive, containing force transformer with at least four three-phased secondary windings, group of rectifier-inverter frequency transformers and driving electric engine with 2P number of poles, connected serially, in accordance to invention, winding of driving electric engine is made of 2P identical coil groups, each one of which is connected to separate three-phased rectifier-inverter frequency transformer, each one of which in its turn is connected to appropriate secondary windings of force transformer with transformation coefficient, equal to 2P. |
|
Method and device for quasi-frequency stepless start of synchronous motor Proposed method and device that can be used, for instance, in gas industry for starting electric drives of gas-transfer units involve connection of excitation unit to field winding, determination of pre-start rotor position relative to stator windings, measurement of voltage across stator windings, current through stator windings, supply voltage and field winding current, evaluation of motor speed by electromotive force induced in stator windings and estimated by voltage across stator windings and current through stator windings, current pulse supply to stator windings with aid of thyristor voltage regulator by sending control signals to control outputs of mentioned voltage-regulator thyristors, regulation of parameter of current pulses supplied to stator windings and field current so that mean torque of machine were higher than motor moment of resistance. |
Another patent 2531190.