DE4241553A1 - Washing machine drive is fed via frequency transformer - features raised secondary resistance of rotor to improve effectiveness at lower speeds - Google Patents

Abstract

A drive motor is for a laundry treatment machine and is fed via a frequency transformer. Its special structural characteristics are described in P4119902.2-32. To provide for further optimisation, the secondary resistance of the rotor is raised to the degree that it corresponds to the requirements of the different thermal and dynamic limiting performance of the motor while taking into account the weakening of the field. ADVANTAGE - The invention improves effectiveness in the lower rotation speed range (washing) and cuts noise.

Description

Against the proposed combined measures A considerable prejudice in the professional world, but without it is not a satisfactory drive to create both the requirements for increased torque in the lower Speed range (washing), as well as good efficiency and silence fulfilled.

It is therefore the task of those mentioned in the claim Improvements to continue a washing machine drive optimize.

Solutions are needed to meet the task became known, after which the Washing machine drive from frequency converter feed of standardized motor larger in size and performance was chosen. However, there is always an associated larger, more powerful frequency converter and because of the poorer utilization of the engine less Efficiency.

If you add the additional costs for the larger engine, the more powerful frequency converter, possibly larger chokes and above all the increased energy costs, so costs are reached which are the additional costs for one Special motor may well exceed.

Above all, the optimization makes a better one Efficiency achieved in the lower speed range (washing), which is known to be by far the most time-consuming part of the job prevails.  

In addition, lower-performing (smaller) Frequency converters are used.

The measures proposed in the claim are therefore operationally very valuable, especially since they also become one further noise reduction when operating the engine contribute.

The increase in secondary resistance can be achieved by both Reduction of the rotor grooves as well as by using Aluminum alloys are made with increased resistance. Both measures are also possible at the same time, especially if with regard to manufacturing requirements a further reduction in the size of the grooves is not possible.

Details of the invention are explained on the characteristic curves of optimized motors. There is
with Md = the torque and
I = the current versus speed.

If you define the current by the multiple of Mdn for any speed point within the acceleration curve (limit values), you get the current for the nominal torque. (Even if such a rough calculation shows deviations from the practical values, this method shows a significant tendency.)
For example for the intersection "a"

1.) - - - = I standard motor Ib / Md max. = 3.75 / 3.75 = 1
        = I special motor Ic / Md max. = 2.5 / 3.75 = 0.65

Since the losses depend on I ² (xR), the ratio is I ² to 0.65 ² = 1 to 0.4.

Even if the calculation of the rollover had an error of 20%, the current is in the ratio of 1 to 0.5. For a practical motor, this would mean that one takes 10 A on the other 6.5 A, with the I ² × R losses being only half.

This is favorable for the engine, although being conceded is that the rotor losses are not the same.

However, for the required frequency converter the losses to the actual electricity, making it smaller can be. The same applies to the chokes.

2.) 1/7 of n / n syn.
- - - I = standard motor = Ie / Md max.g = 4.5 / 2.9 = 1.52 I ² = 2.4
        I = special motor = If / Md max.d = 3.75 / 4.75 = 0.79 I ² = 0.61

So you can see the I ² (xR) losses decrease by about 75%.

This is in the case of a switching operation such as that when reversing (Washing) occurs, of considerable advantage.

A disadvantage is the greater slip at the nominal speed point, However, this can be done without problems by increasing the frequency (around 10%). Max. Speed at full load is only proportionally 1%, because when it is reached the maximum speed is the counter torque and thus the current by spinning off the water and lack of more Power requirement for acceleration immediately to about 1/3 decreases (1/3 I corresponds to only 1/9 of the losses).  

The change of the engine from standard to special execution brings such serious advantages that the prejudice against Special motors is not authorized. It would also be from the standpoint irresponsible of energy consumption, such technical Opportunities not to use.

Claims (1)

Drive motor for a laundry treatment machine, which is fed via a frequency converter and according to the patent. . (Registration: file number P 41 19 902.2-32) is carried out with special, combined design features, characterized in that for further optimization the secondary resistance of the rotor is increased to such an extent that it takes into account the requirements of the different thermal and dynamic limit power taking into account the field weakening of the drive motor of the washing machine.
Through the above registration, a drive unit for a laundry treatment machine is already named, in which the electrical energy is supplied by a frequency converter to achieve different washing and spin speeds, which also performs the tasks of changing the direction of rotation, programming the various accelerations, braking and switching back Speeds at, unbalance takes over.
The motor is characterized by the choice of particularly suitable numbers of slots, both in the rotor and in the stator. The winding is designed as a longed winding and the laminated core is welded together in the back.