MOTOR STARTING – Three-Phase
The transformer for starting the motors is designed to work primarily with large motors. A key characteristic of this type of transformer is the high current due to absorption of the motor during the start-up process, followed by a period of operation at the nominal current. While they may be undersized with respect to the nominal motor current, and the transformers to be connected to the motors, it is always necessary to keep in mind the most appropriate dimensions to ensure proper thermal and mechanical operation during start-up.
field of application – installations of large pumps, turbines, etc.
AUTO-TRANSFORMERS FOR MOTOR START-UP
To reduce the in-rush current of the electric motors, especially on the larger ones, reduced voltages are used compared to the nominal one. The auto-transformer for motor start-up consists of an auto-transformer that usually occurs with sockets of 75%, 70% and 65% compared to the nominal voltage value. This way, the motor is started at a reduced voltage to then be connected to the mains and, finally, the transformer is de-energized. The dimensions with respect to the motor to be started are usually smaller, given that it has very brief operating periods (about 30 seconds). As in the case of transformers for start-up, during the design phase, it is necessary to take into account the correct thermal and dynamic dimensioning. If particular applications are required, the client must establish any voltage drop limits on the motor during start-up.
field of application – start-up of large motors with reduced current