Electrical brake for AC motors

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When thread cutting on the lathe, it is easier if the motor can be braked automatically. This can be done simply by short-circuiting the windings by means of the counter electromotive force generated. For this purpose, the auxiliary switch of the contactor of the drive motor must have 2 free closing contacts. In the case of a single-phase motor, only one phase must be short-circuited via the make contacts of the contactors for both directions of rotation with the second phase via a 2-pole brake switch. With a 3-pole motor, the second phase must also be routed via the make contacts of the contactors, and the third phase is then connected to the short-circuited contacts of the brake switch. The wiring can be found in the wiring diagram. The required auxiliary contacts can be ordered from the contactor manufacturer. Since usually only 2-pole auxiliary switches are installed, these can simply be replaced with a 4-pole auxiliary switch with three make contacts and one break contact.