DE611478C - Single or multi-phase short circuit motor with distributed winding - Google Patents

Description

The invention has the purpose that with short-circuit motors with certain numbers of rotor bars occurring, with high frequency fluctuating documents as well as those with some numbers of bars due to the presence two fields with the pole pair number difference 1 to eliminate vibrating forces and This enables both a smooth start-up of the motor and the machine noise to reduce.

To understand the mode of operation of the constructive measure representing the invention To do this, some results from the theory of the short-circuit motor must be dealt with.

The ordinal number of the upper fields that can be generated by a runner from the number of bars z _a results from the equation

where It _{1 is} the ordinal number of the primary stator field, χ is a positive or negative integer; m and% are also positive or negative numbers, the absolute value of which is the number of poles in the relevant upper field, based on the entire circumference. The ordinal number of the stator fields of a three-phase full-hole winding results from
relationship

n _x - p (i + 6z),

the

wherein ζ represents a positive or negative integer or zero. Positive values of% mean fields running in the right direction, negative values mean fields running in opposite directions.

The fields m, which result from the first equation for χ = 0, should not be taken into account in this context, in which only torques fluctuating over time, because the speed of these fields is independent of the speed of the motor and always equal to that of the generating field; As a result, the torque generated by these fields is also constant at constant speed. If, on the other hand, a rotor generates upper fields from a primary field, the number of poles of which _{corresponds to the number of poles of any other stator fields W 2} , torques arise which, apart from a certain speed at which both fields run synchronously, are variable over time. A distinction must be made between the cases m = W ₂ ¹ ^ m = - W ₂ , m = zn ₂ means that the direction of rotation of both fields is the same at a standstill

*) The patent seeker stated as the inventor:

Dr. Hans Lund in Berlin-Schöneberg.

is, m - - n _% on the other hand, that the fields run against each other when the engine is stopped. In one case, as long as the motor is at a standstill, the torque S generated by the upper fields is constant - in this case the speed is zero at which the fields run synchronously - in the other it fluctuates at twice the mains frequency. The equations for the torques generated by the fields m and « _{2 are:}

= Mdh cos

+ const if m ~

and

M _d -

cos

- ~ t ~ (l— s) (üt - \ - Z ₂ Xy ₀ + const,

<2 + - ~ (1 - s) \ at -f- Z ₂ Xf _0. -J- const, if m =

All fields with the same χ generate the same torque frequency. cp ₀ denotes the position of the traveler at the time i = to and s the slip. When the engine is at a standstill, ι - s = o. In the first case, 1 - s = ο the relationship

Md = Mdk cos (& a # <Po + const). 20th

The equation shows that the torque is constant over time, but depends on the position of the rotor. If it is rotated by a rotor slot pitch φ _ο = -3-Η- it runs through «times

? 2

all values of a period. The fields χ = τ, which are generally more important than the other upper fields, shift against the stator fields «2 when the armature is rotated about its own wavelength, with the torque running through a full period. These torques, which are perceptible when the motor is rotating slowly, are known as slot torques, which cause the motor to hook when the motor is at a standstill.

If one now divides the rotor into two rotors, and this is the idea of the invention, by inserting a third short-circuit ring r in the middle of the rotor or by placing two separate rotors on the same shaft and turning both rotors against each other by half a groove pitch As Fig. ι shows, the torques generated by the fields χ = ι cancel each other out completely. This applies not only to standstill, but also to any speed, and not only for the shafts m = « _a , but also for the shafts m = -%. With the simple measure of inserting a third short-circuit ring, however, not only the pulsating torques are avoided, but also the machine noises that arise as a result.

To offset the grooves of two laminated rotor bodies of an AC motor against each other and the slot conductors of the individual laminated rotor bodies by lying between them To connect short-circuit rings is known per se. Acted in the known arrangements But it is AC motors with pronounced poles. With these machines occur as a result of the inequality of the magnetic resistance between the stator and rotor lying airway dead center positions. In contrast to this, this is the case here Invention about that by upper fields in single or multi-phase short-circuit motors to eliminate dead center positions caused by distributed winding. According to the invention this is achieved in that all upper field moments by dividing the Rotor in axial. Direction by means of one or more short-circuit rings in two or more electrically offset from one another by inclining or offsetting the stator or rotor slots Parts are so out of phase with one another that they cancel each other out completely.

Instead of the stepwise displacement of the rotor slots around the # -th part of a rotor slot arrangement, a corresponding inclination of the rotor slots is of course also possible, as shown in Fig is drawn in with inclined runner grooves b . Furthermore, a corresponding inclination of the stator slots is possible with straight rotor slots. However, the inclination alone does not allow complete compensation of the slot torques; The third short-circuit ring r is essential. An example of a simultaneous offset against the harmonics χ = ι and χ z = 2, whereby four rotor parts and three additional short-circuit rings r are required, is shown in Fig. 3. In order to avoid a rotary movement of the housing as a result of the moments acting on the two machine halves in opposite directions and thus also to eliminate this source of noise, it is advisable to subdivide the rotor so that each two rotor sections symmetrically to the center plane of the rotor have the same offset . An example of such a displacement of the rotor against the waves χ = ι is shown in Fig. 4 _.;

The shaking forces caused by the presence of upper fields with the difference in the number of pairs of poles 1 occur — it is mostly there

Claims (4)

around runner's upper fields X ₁ and x _z - are represented by an equation that replaces the expression ζ _ζ χφ _{0 with} the expression Z ₂ (x _a - X ₁ ) φ ₀ or Z ₂ (x ₂ -f- X ₁ ) φ ₀ contains. It can be seen from this that there is a displacement of the rotor parts or the runner groove 2 (X ^ + X ₁ ) division results in a complete compensation of the shaking forces. Another advantage consists in the possibility of a very strong inclination of the grooves without the Winding factor for the fundamental wave is significantly reduced. ^X 5 claims: i. Single or multi-phase short-circuit motor with distributed winding, characterized in that the rotor is divided into two or more parts in the axial direction by inserting one or more short-circuit rings, which are electrically connected to one another by inclining or offsetting the stator or rotor slots (b or s) are offset. 2. Short circuit motor according to claim i, characterized in that only the stator Has inclined grooves and the runner grooves are neither inclined nor offset are. 3. Short circuit motor according to claim 1, characterized by two symmetrical to Runner sections lying in the middle plane of the runner with the same offset of the runner grooves. 4. Short circuit motor according to claim 1, characterized in that the whole Rotor body made up of two or more single cage rotors sitting next to each other on the shaft composed. 1 sheet of drawings