DE646114C - Induction motor for connection to single-phase networks - Google Patents

Description

The induction motors used for connection to a single-phase network are often used provided with an auxiliary winding with which a capacitor is connected in series to to obtain an increased starting torque. This capacitor can also be used during operation remain switched on continuously in order to improve the operating conditions of the engine. The most favorable operating conditions

ίο result with a capacitor of relatively small capacity, with which the motor can only develop a low torque when starting, which is approximately Y _{3 of} the nominal torque and in many cases is insufficient. In order to achieve high starting torques, one must therefore choose the capacitance of the capacitor at start-up to be considerably larger than during normal operation. By increasing the capacity, the power consumption of the auxiliary phase circuit is increased considerably, so that the auxiliary phase winding is heavily loaded.

In order to avoid overloads, the capacity must therefore be restored after the start-up can be reduced in size. For this purpose, the capacitor is often subdivided and a part is switched off after the start-up, for example by means of a centrifugal switch. The arrangement of a centrifugal switch or other switching device is cumbersome and disadvantageous.

According to the invention, without using a switching device and without switching off some of the capacitors have a high starting torque and good operating properties of the engine can be obtained by having one in series with the whole Motor circuit lying capacitor such a multiple of the capacity of the im Auxiliary phase circuit that receives the total current of the motor when the capacitor is located Start-up is in phase with the mains voltage.

While it is known to have a capacitor in series with the entire motor circuit and to arrange the auxiliary phase circuit including a capacitor to thereby to achieve phase compensation during operation, so that the motor only Active current consumes. The capacity of the in series with the entire motor circuit lying capacitor, is not larger, but rather even smaller than the Capacity of the capacitor located in the auxiliary phase circuit and is therefore capable of during no phase-improving effect during the start-up.

In contrast to this known circuit, the invention is based on the knowledge that by connecting a capacitor in series to the entire circuit of the motor a considerable increase in the tightening torque can be achieved if the

*) The patent seeker stated as the inventor:

Dipl.-Ing. Friedrich Bauer in Berlin-Charlottenburg.

both capacitors can be dimensioned in the manner described above. the Invention has the great advantage that the main capacitor during the short Starting period is heavily used because it carries the full starting current, so that with small capacities high capacitive reactive powers can be obtained. While During normal operation, the main capacitor only carries low voltages, since the Operating current is much smaller than the starting current and therefore also smaller Voltages generated on the capacitor. The particular one made according to the invention

i _S dimensioning of the capacitors it is possible to achieve full utilization of the capacitors without the use of switching devices during start-up and during operation.

An embodiment of the invention is shown schematically in the drawing. At the single-phase network io is the main winding 12 and the main switch Ii Auxiliary winding 13 of the single-phase induction motor connected. In series with the Main winding 12 is the main capacitor 14, while the auxiliary phase circuit Auxiliary capacitor 15 is located. The two capacitors 14 and 15 are permanently switched on, namely, the main capacitor 14 has a much larger capacitance than the auxiliary capacitor 15, which is dimensioned so that no phase shift between the total current of the motor and the mains voltage occurs at start-up.

Between the reactance of the auxiliary winding 13 and the capacitance of the auxiliary capacitor a certain ratio is advantageously maintained in order to achieve a nominal load to achieve as perfect a rotating field as possible. This is usually done through such a Dimensioning of the motor winding and the capacitance of the auxiliary capacitor achieved that when bridging the main capacitor 14, the tightening torque is about 30% of the nominal torque amounts to. Tests and calculations show that the main capacity 14 is essential Must be greater than the auxiliary capacity 15. For example, the ratio of the two Capacities are about 1:10.

A current transformer can also be used between the main switch 11 and the motor switch on, so that one can choose the capacity and the voltage stress for the capacitor 14 has the greatest possible freedom. You can also use the combine the two capacitors 14 and 15 to form a common capacitor, whereby only a tap is led out of the capacitor. They can also Capacitors with the motor in the usual way with the known capacitor motors Way to be assembled.

Claims (4)

Patent claims: 1. Induction motor for connection to single-phase networks in series with one Auxiliary phase winding and the entire motor circuit lying capacitors, characterized in that the in Series with the entire motor circuit lying capacitor such a multiple the capacity of the capacitor located in the auxiliary phase circuit has that the total current of the motor at start-up in Phase with the mains voltage. 2. Device according to claim 1, characterized in that the auxiliary phase circuit lying partial capacitor is dimensioned so that the motor by bridging the lying in the main circuit Capacitor developed about 30% of its nominal torque. 3. Device according to claim 1, characterized in that the two Partial capacitors are structurally combined. 4. A device according to claim 1, characterized in that the two capacitors are combined into a single con- _go capacitor, which is provided with a corresponding tap. 1 sheet of drawings