ESA 1-phase

This is the simplest design of the soft start up devices. Here the advantage is taken that the asynchronous motor can create a rotating field only when all the three phases conduct the voltage. No sooner the motor contactor connects the voltage to the device the two phases are immediately located on the motor. The third phase is controlled within the eligible start up time. The motor runs very slowly. At the end of the start up time the bypass contactor (internal/external) connects the controlled phase, so that the semiconductor is unloaded and the unwanted radiations as per the EMV-regulations can be avoided. This principle is in accordance with the ESA (single phase-Soft-Startup).

These devices require lowest circuit complexities; provide higher operational security and are very easy to use. The rotating current motors can be operated on 1ph- Circuit with condenser in the Steinmetz circuit. Operation as the start up current limiting for other 1ph-User load like transformers is also possible. A switching contact serves for switching the supply for electronics, so that the controlled phase is switched off and in case of a new switching a renewed controlling can take place. This contact can be used in case of pole-changeable motors for improvement of disposition of repetition.

Both the uncontrolled phases clearly lead to more current than the controlled ones. Hence these are not suitable for heavy starting. As always the operation voltage should be switched and the uneven current distribution heats up the motor very strongly; the possible switching frequency against the other systems is less.