DE20021290U1 - Circuit arrangement for electronic stop detection in synchronous motors - Google Patents

Description

Circuit arrangement for electronic stop detection in synchronous motors

The invention relates to ensuring a defined shutdown behavior of synchronous motors.

When carrying out positioning operations with synchronous motors, end positions are usually detected using limit switches in a mechanical, inductive or optical manner.

For example, the use of mechanical solutions to make the adjustment processes more precise is a dubious solution, as the exact adjustment path or angle depends on the assembly tolerances. In systems that implement a locking function, such uncertainties require a complex mechanical solution, as the motor may only be switched off when, for example, the locking process is actually complete. In addition, there are problems associated with the wear and tear of mechanical systems and the necessary adjustment.

A second possibility is to switch on the synchronous motor in an open control chain for a certain distance or a certain time according to DE 200 08 483.6 Ul. In this case, the phase position of the voltage applied to the two motor coils is measured and the switch position and thus the direction of rotation is determined. To carry out the control process, the motor is switched on using only one remaining switching element after the direction of rotation or control has been preselected. Starting with the switch-on process, the evaluation electronics count the number of periods that the motor is switched on.

After reaching the number of periods, which corresponds to a specified value and thus a certain travel or angle, the motor is switched off again using one of the switching elements.

The disadvantage of this solution, in addition to the wear problem, is the noise generated if the motor is already at the limit and is still powered for a certain time.

Furthermore, there is no feedback as to whether the system has actually reached the stop.

The object of the invention is therefore to propose a circuit arrangement with which an end stop is detected and the motor is switched off. An inventive solution to this object is specified in claim 1. Further developments of the invention are characterized in the subclaims.

According to the concept of the invention, the peak values of the voltages on the two motor phases A and B are determined over several periods. In the event that an end stop is reached, the voltage drop of the winding supplied via the motor capacitor Cl changes significantly and can therefore be evaluated. In this way, an end stop is immediately detected and the motor is switched off.

The main advantages of the new solution are that the system can independently recognize a given setting range and that wear and noise are minimized.

The solution is suitable for both rotary and linear synchronous motors.

Further details, features and advantages of the invention emerge from the following description of an embodiment with reference to the associated drawings in Fig. 1 and 2, which illustrate two preferred embodiments of the new shutdown control for synchronous motors.

Fig. 1 shows the diagram of the new electronic stop detection for synchronous motors using a first circuit arrangement for shutdown control. The circuit comprises the main components motor 4 with motor phases 4.1 (A and B), motor capacitor 5 (Cl), evaluation and control electronics 6 and switching element for switching off the synchronous motor when an end position is reached. The direction of rotation of the synchronous motor 4 is preselected using switch 8.

For example, the measured values for the voltage drops and/or the potential differences are recorded via measuring points 1 to 3 and evaluated in the evaluation and control electronics 6.

If the actuator reaches an end stop, there will be a significant change in the voltage drop of the motor phases 4.1 supplied via the motor capacitor 5.

As a result of this voltage drop, the switching element 7 is activated by the evaluation and control electronics and the current supply to the motor 4 is interrupted.

A second circuit arrangement for switching off synchronous motors, which uses the new principle of electronic stop detection, is shown in Fig. 2.

The circuit is advantageous when the motor 4 is not operated directly via a direction switch 8, as shown in Fig. 1, but there is a higher-level control 9 or just two (not shown) buttons, e.g. operated with low voltage, which are intended to trigger the actuating movement. In this case, the evaluation and control electronics 6 are integrated into the control circuit between the button and the switching elements. The switching element 7 from Fig. 1 can be omitted as an additional element, because the switching elements in the motor supply lines 10 can also take over the function (connecting the motor to and disconnecting it from the power supply).

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List of reference symbols

1 Measuring point 2 Measuring point 3 Measuring point 4 engine 4.1 Motor phases 5 Motor capacitor 6 Evaluation and control electronics 7 Switching element 8th Switch for direction of rotation 9 higher-level control 10 Switching elements in the motor supply lines

Claims (6)

1. Circuit arrangement for electronic stop detection of synchronous motors, characterized in that a) the voltages of the two motor phases A and B ( 4.1 ) at the measuring points ( 1 , 2 ) relative to the mass ( 3 ) or the potential difference between the two motor phases A, B ( 4.1 ) at the measuring points ( 1 , 2 ) is measured, b) these voltages are evaluated directly via an evaluation and control electronics ( 6 ), or the potential difference between the two motor phases ( 4.1 ) and/or their spectrum are evaluated and, if the criterion for reaching an end stop is met, the current supply to the motor ( 4 ) is interrupted via the switching element ( 7 ). 2. Circuit arrangement according to claim 1, characterized in that the criterion for reaching an end stop is the change in the voltage drop of the phase supplied via the motor capacitor Cl ( 5 ). 3. Circuit arrangement according to claim 1, characterized in that a change in the curve shape of the evaluated voltage serves as a criterion for reaching an end stop. 4. Circuit arrangement according to claim 1, characterized in that a change in the potential difference between the motor phases A, B ( 4.1 ) serves as a criterion for reaching an end stop. 5. Circuit arrangement according to claim 1, characterized in that a change in the spectrum of the voltage of the phase supplied via the motor capacitor C1 ( 5 ) serves as a criterion for reaching an end stop, wherein the spectral components are preferably increased at n . 1.5 times the operating frequency. 6. Circuit arrangement according to one of claims 1 to 5, characterized in that either a permanently stored value or determined values from previous periods are specified as the reference value for reaching the criterion.