Electrical engineering & Electromechanics (Aug 2015)
COMPARISON OF CHARACTERISTICS OF THE CONVERTER-FED MOTOR AT SUPPLY FROM THE SINGLE-PHASE NETWORK AND FROM THE SOURCE OF THE DIRECT CURRENT
Abstract
Purpose. Now even more often in various cars and mechanisms converter-fed motors are used. Their comparative characteristics with motors which are supplied from a network of a direct current are necessary for definition of the specific moment of motors which are supplied from the single-phase alternating current main. Methodology. For the converter-fed motor with a ratio of teeth of the stator and a rotor 8/6 at supply from a single-phase network via the rectifier two groups of numerical experiments were carried out. Motor capacity with a constant frequency of rotation at various capacity of the capacitor at the exit of the rectifier and motor capacity at the current providing the most admissible excess of temperature of a winding are determined. Dependences of useful power on capacity size at the rectifier exit are received with a constant frequency of rotation, and also at invariable current. Results. On the basis of the made numerical experiment it is possible to conclude that due to fluctuation of tension (from 0 to 100 %) at the rectifier exit at power supply of the converter-fed motor from the single-phase alternating current main in comparison with the corresponding sizes at supply from a source of a direct current: • motor capacity at preservation of capacity of the capacitor at the exit of the rectifier and frequency of rotation decreases on 60 – 63 %; • at almost acceptable increase in capacity of the capacitor (approximately twice) power should be reduced by 50 %; • power deceleration at preservation of that size of current of the motor what took place at its food from a source of a direct current makes 40 % at preservation of size of capacity of the capacitor at the exit of the rectifier and 32 % at its doubling, the frequency of rotation decreases approximately on 13 – 15 %. Practical value. The specific moment can be determined by power sizes at single-phase supply, frequency of rotation and to the volume of a rotor, with an invariable frequency of rotation it decreases in comparison with the specific moment at power supply of the motor from a source of a direct current by 50 – 63 %.
