Electrical generator or motor structure – Dynamoelectric – Rotary
Utility Patent
1999-09-21
2001-01-02
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06800R, C310S064000, C310S089000, C310S160000, C310S083000, C310S099000
Utility Patent
active
06169345
ABSTRACT:
The invention concerns a compact drive with an electric motor, a frequency converter and a gear.
The motor is an alternating or a three-pulse current motor. Also permanent magnet motors, switched reluctance motors or direct current motors can be used. The motor is supplied by the frequency converter and delivers its mechanical output via the gear.
The purpose of the invention is to make a compact drive as compact as possible.
In a compact drive as mentioned in the introduction, this is solved in that the frequency converter is arranged at one front end of the motor and the gear is arranged at the other front end of the motor.
This embodiment involves several advantages: Firstly, there is a clear separation between the electrical supply taking place on one side of the motor, and the mechanical power output taking place on the other side of the motor. The length of the drive will increase somewhat due to this measure. However, it can be ensured that both gear and frequency converter have substantially the same cross-sectional area as the motor, so that laterally fitted parts can be avoided. Secondly, the motor will need fewer housing parts, as the front covers of the motor are replaced by the frequency converter and the gear, respectively. Thus also the axial extension of the drive caused by the gear and the frequency converter can be kept within reasonable limits. Further, the production of such a compact drive is more simple. Normally, the stator winding has its connections in the area of a front end of the motor. When the frequency converter is connected here, the cables are kept short. The connections are correspondingly easier to wire and connect. Here, the terms “frequency converter” and “gear” are used as common terms. The frequency converter can be made so that it converts a direct current into a one- or multi-phase alternating current, or converts a one- or multi-phase alternating current into a direct current or an alternating current with a different frequency. The gear converts the mechanical energy defined by the speed and torque of the motor shaft to a different form, that is, a different speed or a different torque, or even to a different sort, for instance hydraulic or pneumatic pressures. In this case the gear is a pump.
In a preferred embodiment it is provided that the frequency converter has a frequency converter housing with a bottom plate of a heat conductive material, which bottom plate is fitted on the stator of the motor. The housing of the frequency converter can therefore be made with reduced stability. The actual stability is obtained in that the housing of the frequency converter is fitted on the stator of the motor. However, the stator of the motor is an extremely stable part, and correspondingly, it also stabilises the housing of the frequency converter via the bottom plate. Usually, the frequency converter is the part of the compact drive producing most heat. This is caused by electrical losses during the frequency conversion, that is, the conversion of a d.c. to an a.c. or the conversion of an alternating voltage. Making at least the bottom plate of a heat conductive material causes that the heat can be distributed and then given off to the surroundings via this bottom plate. In many cases an additional cooling will not be required.
It is also preferred that the gear has a baseplate of a heat conductive material, which baseplate is fitted on the stator of the motor. The facts applying for the bottom plate of the frequency converter also apply for this baseplate. The baseplate is mechanically stabilised by the stator of the motor, which is the mechanically most stable part of the compact drive. The heat produced can be distributed and then given off to the surroundings via this baseplate. The dimensions of the gear housing can be correspondingly weaker, as the motor serves as stabiliser.
Preferably, the bottom plate and/or the baseplate are in heat-conductive connection with the stator. The heat from the frequency converter or the gear, respectively, is no longer just given off to the surroundings. Through the bottom plate and/or the baseplate it can be led into the stator. The stator, which normally has a larger metal mass than the frequency converter, can absorb this heat. Additionally, it also has a larger heat-emitting surface, via which the heat can be given off to the surroundings. This causes that practically no additional cooling measures, such as forced ventilation etc., must be taken. Still, a thermally stable operation is obtained in spite of the compact dimensions.
In a particularly preferred embodiment it is provided that the bottom plate and/or the base plate have a bearing housing for the rotor of the motor. Thus, the rotor is carried in the bottom plate of the frequency converter and/or the baseplate of the gear, respectively. This saves an additional bearing in the gear. The gear “shares” a bearing with the motor. In connection with the frequency converter this has the additional advantage that also via the rotor bearing there is a certain heat emission. Of course, this heat emission is limited, as only a limited heat flow can be transported via the bearing. In total, an additional equalisation of the temperature distribution and a reduction of the peak temperatures can be observed. This construction also facilitates the assembling. The compact drive can be assembled by placing the frequency converter and the gear from both sides on the stator. Thus, the rotor is also automatically carried in the stator.
It is particularly preferred that the bottom plate and/or the baseplate have a circumferential centring projection in the area of its circumferential edges next to the motor, which projection surrounds the stator. This provides that the bottom plate or the baseplate, respectively, are fitted with a predetermined orientation in relation to the stator, so that also the bearing housing for admission of the bearing is oriented concentrically in relation to the stator bore. No further orientation measures are thus required. This facilitates the mounting considerably. Additionally, this measure secures against a lateral displacement of the frequency converter or the gear, respectively, in relation to the motor. The circumferential centring projection can also be interrupted, as long as it secures that the concentric orientation of the frequency converter or the gear, respectively, in relation to the motor is maintained.
It is particularly preferred that the bottom plate and/or the baseplate are made of aluminium. On the one hand aluminium has the desired heat conductivity and on the other hand it has the required mechanical stability for admission of the bearing housing. These advantages are combined with a low weight, so that the compact drive can not only be kept small with regard to its dimensions, but also with regard to its weight.
Advantageously, the frequency converter and the gear are clamped together, thus holding the motor between them. Thus, no additional fixing opportunities are required on the motor. The motor is held between the frequency converter and the gear by means of clamping forces. Fixing opportunities are thus only required on the frequency converter and the gear. This facilitates both the production of the individual parts and the assembling of frequency converter, motor and gear.
It is also advantageous that the circumference of the stator has immediate connection with the surrounding atmosphere. In this connection, a protective shield, that is, a housing, for the motor is abandoned. The circumferential surface of the stator can then be exposed to the surrounding atmosphere, usually the surrounding air. Thus also the occurring heat can quickly and reliably be dissipated, without requiring a forced guiding or a moving of the cooling air. As stated above, a certain amount of heat is also led to the stator from the frequency converter, which will cause the motor to get hot during operation. However, a balance between the heat admission and the heat dissipation occurs, so that the permitted temperatures are not exce
Bloch Jesper Olsen
Jensen John Børsting
Kristensen John
Danfoss A/S
Lam Thanh
Lee Mann Smith McWilliams Sweeney & Ohlson
Ramirez Nestor
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