DE696636C - Circuit to prevent the mechanical brake from being applied in three-phase motors with a shift control for the mains connection, which reverses the direction of rotation - Google Patents

Description

.A'8310

The main patent 679 940 describes a circuit for preventing the mechanical brake from being applied in three-phase motors - with a sliding armature, which prevents the sliding armature from falling off during the reversal of the direction of rotation caused by the gradual swapping of two mains connections. The undesired dropping of the sliding armature, which is often associated with broken cables, is avoided by connecting all phase windings in series at the moment of the actual phase change, so that the root mean square of the induction is significantly higher than with the known formation of fields with three times the number of poles Connection of only one small iPhase winding to the same voltage despite the same arithmetic mean and the magnetic pulling force is sufficient to prevent the brake from engaging.

However, if the saturation of the machine is too weak, the field strength of the series is sufficient lying windings during the switching process not to prevent the sliding armature from falling off to avoid, according to the invention, in the switching stage with all the phase windings connected in series, the Field strength increased for a short time by stepping up the voltage or by a special auxiliary winding.

It is known per se, with electric motors in the control periods by Hoclitransformieren the tension or through. Changing the winding circuit increases the field strength. heights. However, this measure was previously '' when reversing sliding anchor motors, ' not yet applied to achieve a sufficiently * high magnetic pull. :

The switching arrangement according to the invention for preventing sliding anchors from falling off for three-phase displacement armature motors is shown in the accompanying drawing. ;

Switching stage ι gives the circuit · of the stator winding of the sliding armature motor in clockwise rotation again / seen from the drive side. In stage 2 the delta connection is on one; Corner solved.

While in the circuit according to the main patent the released winding phase is short-circuited in the third stage and all winding phases in series are connected to two mains phases in the fourth stop position, a transformer A is now switched on in stage 3. The three-phase supply is always maintained. In the fourth switch position, all three winding phases of the split delta connection are connected in series to two mains phases. Level 5 corresponds to =% tvd e 3, swapping two mains connections, while switch position 6 represents the changeover of two mains phases carried out to operate the motor in opposite directions. The measure according to the invention achieves. that even with weakly saturated machines there is always a field of sufficient strength to prevent the sliding armature from falling off and thus preventing the mechanical brake from engaging.

Claims (1)

Claim: Circuit to prevent the mechanical brake from being applied in three-phase motors with sliding anchor during the step-by-step swapping of two Mains connections caused the direction of rotation to be reversed according to patent 679940, characterized in that that in the switching stage with series connection of all phase windings the field strength by stepping up the voltage or by a Auxiliary activity is increased for a short time. 1 sheet of drawings Berlin. - printed in öes reichsdruckerM