CONTROL OF EXCITATION CIRCUIT PARAMETERS OF SYNCHRONOUS MOTORS AT START-UP AND SELF-START

Synchronous motors (SD) with excitation systems (SZ) have a significant specific weight in ensuring continuous and complex technological processes at enterprises of the metallurgical, chemical, and petroleum processing industries. Existing types of industrial mechanisms and machines require different starting and input moments in the operation of the SD. Depending on the requirements of technological processes, the following circuit solutions are proposed to solve the problem of starting powerful synchronous high-voltage motors: direct asynchronous start with control of the excitation circuit parameters; start-up with control around the stator of the LED using devices that change the energy parameters of the power source; starting with the use of auxiliary electric machines and mechanisms. During a direct asynchronous start of a synchronous motor, an increase in electromagnetic torque can be achieved through the use of special methods of controlling the excitation circuit. This may include cyclic regulation of the excitation voltage, gradual or stepwise reduction of the resistance of the starting resistor, as well as their combined use. More complex control of the excitation system, the use of starting inductive resistances, excitation systems with two-way conductivity converters, and the use of capacitive energy storage in the excitation circuit are also possible. Additionally, it is possible to introduce changes in the design of the stationary motor itself, such as the use of split excitation windings with series capacitors or the arrangement of capacitive excitation rods. A significant increase in the asynchronous moment of the LED at a reduced voltage can be obtained by cyclically introducing capacitive energy storage devices (EEE) into the excitation circuit. The use of ENE allows to reduce the phase shift between the E.R.S. and OZ current with a simultaneous increase in the if current and its active component, as well as use the stored slip energy, which leads to an increase in the asynchronous torque. The supply of forcing voltage to the OT with the simultaneous inclusion of the ENE ensures a further increase in torque. The article discusses the scheme of the device during cyclic control of the LED excitation circuit parameters. To evaluate the effectiveness of the cyclic control of the parameters of the circuit, the transient processes of the asynchronous operation of the SDS3 2000–100 type with a power of 2000 kW, 100 rpm were calculated. Calculated dependences of direct asynchronous start of the LED, as well as with cyclical changes in the parameters of the excitation circuit, are given. For a comparative assessment, calculated dependences on the ENE with cyclic changes in the parameters of the excitation circuit were performed. The analysis of calculated dependencies shows that with the inclusion of ENE in the OZ, the input torque increases by 22% compared to the resistor start with a corresponding increase in the OZ current amplitude by 39%. The maximum value of the transient voltage Ufmax when the ENE is turned on exceeds the transient voltage on the OZ by only 7% when starting the LED with a seven-fold starting resistor.