DE3432946A1 - IRONLESS COLLECTORLESS DC MOTOR FOR HIGH SPEED - Google Patents

Description

² ARTHUR PFEIFFER VAKUUMTECHNIK WETZLAR GMBH Ironless brushless DC motor for high speeds

The invention relates to a brushless direct current motor for high speeds, according to the preamble of the claim 1, for driving e.g. turbo molecular pumps, gyroscopes, spinning or grinding spindles, especially magnetically mounted Rotors.

The vast majority of high-speed machines are now powered by three-phase motors. Disadvantage of these engines is the decreasing efficiency with increasing air gap between rotor and stator due to the increasing magnetizing current. Brushless DC motors with a wound sheet metal stator and rotating permanent magnetic Although rotors do not have this disadvantage, they exert radial attractive forces between the rotor and stator, which in the case of radial magnetic bearings must be compensated for by additional bearing forces. From the German patent application P 3302 839 a motor is known that does not have these disadvantages and in which an ironless winding in a multi-pole magnetized air gap protrudes. Two-pole arrangements are difficult to implement with the help of this design, since there is no space for the winding heads. Four-pole arrangements require twice as much to drive them Running frequency, which leads to higher switching losses in the supply device and higher eddy current losses in the wires of the winding leads. In addition, the manufacture of such a winding is very complicated and it requires a large air gap.

Brush-commutated DC motors with ironless ones are also available Skewed windings are known, as they are at Faulhaber (Fritz Faulhaber: Simple calculation bases for rapidly starting DC servomotors, VDI-Z. Vol 107 No. 4, pp. 149-152)

be written. These motors do not have any radial force, but not suitable in a vacuum or for very high speeds because of the commutator.

The object of the invention is to present a motor which, and in particular, avoids the disadvantages indicated above with a small air gap with a simple stable winding without end windings a drive free of radial forces a wave with low losses.

The object is achieved by an arrangement as described in the characterizing part of the first patent claim will. The inventive design of the oblique. winding in four partial windings, all of which start with one Pole and its ends via four controllable electrical switching elements with the other pole of the operating voltage source are connected, it is possible to use commercially available direct current drive devices (operating instructions for turbo molecular pumps TPH 170, TPU 170 and drive electronics TCP 300 No. PM 800 093 BD, E, F from Arthur.Pfeiffer Vakuumtechnik Wetzlar GmbH).

The winding sections are controlled with the aid of two Hall probes which are mounted as described in claim 2 are.

With an even air gap induction, the from the skewed winding induced back EMF a sinusoidal curve, which is disadvantageous for the operating voltage source. When designing the pole faces according to claim 3 can by the reduced air gap induction in the center of a pole of the arc the sinusoidal back EMF flattened and thus a constant back EMF of the motor can be generated. The use of a winding protruding from the air gap according to claim 4 enables heat to be dissipated from the winding, which is particularly advantageous in a vacuum.

A preferred exemplary embodiment of the invention will be explained in more detail below with the aid of FIGS. 1-3.

Fig. 1 shows a development of the helical winding with the position of the Hall probes and schematically the current flow, 2 shows a cross section through the motor in the plane of the Hall probes

and FIG. 3 shows the longitudinal section of an exemplary embodiment. .

The housing in which the arrangement is located is denoted by 9.

In a rotor 1 with the rotor shaft 7 made of steel, which is mounted in the end shields 10 with two magnetic bearings 8 is, an iron return sleeve 2 with radially magnetized magnets 3 is installed. In the one between bell and Rotor shaft formed air gap 11 is a housing-fixed stator coil 4 is arranged, which with its lower end from the The rotor bell protrudes and is enclosed by a support sleeve 6 made of aluminum. This conducts the in the stator coil resulting heat loss to the housing. The Hall probes 5 are on the inside of the stator coil in the wall of a cylindrical thin-walled sleeve of insulating material attached. With 12 emergency bearings and with 13 axial support bearings are designated.

Fig. 1 shows in its upper part the development of the stator coil. Starting at al, the winding runs over half Circumference to the opposite edge and from there goes back to the starting point on the back. From there the next turn parallel to the first. By analogous continuation of this type of winding, a continuous two-ply is obtained Winding, the number of turns, length and diameter of which depend on the wire thickness. The winding is in four equal partial windings divided, whose beginnings are connected at a1 and whose ends a2-a5 each to a collector of a switching transistor to lead. If the pole dividing line of the rotor exceeds the Hall probe Hl, transistor Tl is switched on. After a quarter Revolution, the pole dividing line exceeds the Hall probe H2,

so transistor T1 is switched off and transistor T2 is switched on etc. To generate the control signals, the output voltages of the Hall probes are each amplified via a preamplifier and the output voltages are fed to a known 1 out of 4 decoder, which is 90 ° offset, 90 ° one revolution continuous pulses to control the transistors Tl to T4 generated.

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Claims (4)

ARTHUR PFEIFFER Vakuumtechnik Wetzlar GmbH Ironless brushless DC motor for high speeds. Claims 1.) Brushless DC motor to drive a high-speed one Rotor consisting of a bell and an associated central rotor shaft (7), which has a radial Air gap (11) with two 180 ° wide magnetic poles (3) and an ironless stator coil (4), which are in these Air gap protrudes, two Hall probes (5) for scanning the position of the rotor and four electrical switching elements, which are controlled one after the other by electrical signals from these Hall probes, characterized in that the The stator coil consists of a helical winding according to FIG. 1 with four identical winding sections, the beginnings of these windings all with one pole and the ends of the winding sections via four controllable electrical switching elements are connected to the other pole of the operating voltage source. 2. Commutatorless direct current motor according to claim 1, characterized in that that the Hall probes Hl and H2 on the inside or outside of the winding on the same surface lines how the beginnings of winding sections 1 and 2 lie. 3. Commutatorless direct current motor according to claims 1 and 2, characterized in that a 180 ° wide magnetic pole two 90 ° wide magnetized magnet segments parallel to their symmetry. 4. Commutatorless direct current motor according to claims 1 and 2, characterized in that the winding is longer than the magnetized There is an air gap, and the protruding part of the winding is attached to a support tube with good thermal conductivity is.