DD291897A7 - DIGITAL CONTROL METHOD FOR MOTORLESS MAGNETIC FIELD DRIVERS - Google Patents

Abstract

The invention relates to a method for digital control of motorless Magnetfeldruehrern, with the number of steps for the permanent magnetic stirring element is doubled. Typical applications are in chemical and biotechnological research, development and industry where both high performance laboratory and small scale instruments are used. Existing motorless magnetic field rotors can be retrofitted with this method and thus achieve a higher stability. According to the invention, this object is achieved by electromagnetically doubling the number of steps of the stirring element for one rotation. Control, digital; Research, biotechnological; Research, chemical; Klein True listeners; retrofitting; Step number; Stability, higher}

Description

embodiment

2 shows an example of a motorless Magnetfoldrührer with 3 pole pairs.

The pole pieces 8 with the magnetic coils 9 are annularly surrounded by the core 7 and point to the center. The respective opposite coils are connected so that they are to be considered electrically as a coil, which is interrupted at the pole pieces in their magnetic FIuU. The respective opposite pole pieces each form a magnetic pole pair upon electrical excitation of the coil.

The stirring element, consisting of a permanent magnet, is located in the center of this arrangement. It depends on the poles which are in each case on the pole shoes.

In the usual operating mode, the coils are cyclically excited and the stirring element performs a movement of 60 ° from coil to coil.

The control method according to the invention introduces an additional step.

If one coil is energized, the next step is added in the second step. The stirring element assumes an intermediate position between the coils, it performs a movement of 30 °. In the next step, then the first excited coil is turned off, the stirring element moves in turn by 30 ° and aligns with the second coil.

If you proceed in the same way in the next steps, the number of steps for a complete revolution is doubled and the stability increased.

For do'.i period, where two coils are energized, a S'.rom reduction for äie coils is effective. By this measure, a uniform magnetic rotating field is generated and thus avoided an additional burden of Leistungsquelk.

During the waiting time before and after a stirring process, all coils are de-energized in order to avoid unnecessary heating of the coil system of the magnetic stirrer.

Claims (4)

1. A method for the digital control of motorless magnetic field stirrers (6) with at least two coils, which are supplied via a switching device (4) from a power source (5) via Irr.pulse from a counter (2) with adjustable clock frequency (1) be controlled, characterized in that a logic circuit (3) between the counter (2) and the switching device (4) is used, the coils (9) by the logic circuit (3) in the direction of rotation overlapping in time from the power source (5) or shut off. 2. A method for the digital control of motorless magnetic stirrer according to claim 1, characterized in that the temporal overlap is chosen so that in the first third of the on time of a coil (9), the preceding still remains on and in the last third of the on time of a coil (9 ) the following coil (9) is already turned on. 3. The method according to claim 1, characterized in that at the turn-on time of two coils (9), the current supplied from the power source (5), for each of the switched coils (9) in the power source (5) reduced by up to 50% becomes. 4. The method according to claim 1, characterized in that during the waiting time before and after a stirring all coils (9) are switched off by the logic circuit (3). For this 1 page drawings Field of application of the invention The invention can be used in chemical and biotechnological research, routine and industrial. It is suitable for high-performance laboratory stirrers as well as for small stirrers with one or more stirring points. Characteristic of the known state of the art Motorless magnetic field stirrers of conventional design usually consist of a star-shaped arrangement of at least two or more electromagnetic pole pairs. Above the center of these pole pairs is located in the mixing vessel, the stirring element, which is set by cyclically driving the coils of the electromagnet in a Drehbev eejung. Each time after a rotation of the stirring of z. B. 90 ° in two pole pairs umzupolen the magnetic field. The control of the coils via power stages, which are controlled by a counter. By varying the counter clock frequency, it is possible to change the speed of the rotating magnetic field. The stability and the synchronism of the stirring element depend essentially on the bundling of the magnetic field and the number of pole pairs. An increase in the number of poles are mechanical limits set, and additional design measures, such as filler, Mu metal plates and auxiliary pole cores, shown in the invention DE 3135961, DE 3400724 and DT 2709365, are complex and limited in the scope. Object of the invention The aim of the invention is to increase the scope of application of a motorless magnetic stirrer and thus save working time and equipment. Existing motorless magnetic stirrer should be retrofittable with this method and thus achieve the quality of the new Systome, without having to intervene mechanically in the special coil system. Explanation of the essence of the invention The invention has for its object to find a method for digital control for motorless magnetic stirrer that is significantly improved in conventional magnetic stirrer systems, the synchronization and the stability of the stirring at different viscous media and thus be avoided under normal operating conditions Trudelerscheinungen and stoppage of the stirring. The solution of the task is carried out according to the invention. ^! nd the number of magnetic sectors of action for the stirring element is doubled. In this case, it is irrelevant how many coils (one coil = one pole pair) of the magnetic field stirrer. The doubling takes place without a mechanical change of the stirrer. In the previously known solutions, the guidance of the stirring element is carried out by cyclically exciting the individual coils. If now a second subsequent thereto is connected to an excited coil, the stirring element assumes a middle position between the coils. It is generated in this way, a magnetically stable intermediate step for the stirring. If one proceeds in the same way for a complete revolution of the stirring element, then one doubles the number of magnetically stable steps for one revolution. The inventive method for controlling magnetic field stirrers increases their performance compared to the known prior art. The application width of the magnetic field stirrer expands considerably. It can be stirred media of higher viscosity. Small particles in the medium and also not quite equal bottom of the mixing vessel do not disturb the stirring process.