Designing a series of motors , especially a basic series, is a task with significant market implications. Therefore, before designing, it is essential to conduct thorough research and comparative analysis of existing series or similar motors both domestically and internationally, adhere to the aforementioned requirements, and provide a practical basis for the overall design by prototyping a few typical specifications. Ms. Can will discuss with you today the issues that must be considered during the design of a series of motors. A good design can achieve multiple specifications of products using the fewest possible components.
1 power level
The ratio of two adjacent power levels in the same series (higher power to lower power) is called the power increment factor or capacity increment factor K. Its value directly affects the determination of the number of power levels in the entire series and has an important impact on the series' economy.
A smaller K value allows for a wider range of power ratings, making it easier to meet the diverse needs of different users, facilitating selection, and reducing over-installation capacity, installation costs, and operating expenses. However, an increase in power ratings leads to more specifications within the same series of motors, requiring more manufacturing equipment and complicating production management, thus increasing manufacturing costs. To address this issue, national standards include specific provisions regarding priority coefficients.
Using a priority number system allows for reasonable segmentation, satisfying the drive needs of various equipment with the fewest possible specifications. In this case, the ratio between the installed capacity of each stage and the motor's own power is approximately equal, which is reasonable. However, considering that the actual demand for different specifications of motors within the same series varies—lower-power motors generally require more, while higher-power motors require relatively less, and certain power ratings may require significantly more or less—it may not be appropriate to use the same power increment coefficient for the entire series, i.e., using only a basic priority number system with the same common ratio. Therefore, the standard stipulates that, when necessary, a composite priority number system is permitted, meaning different priority number systems are used within different power ranges. This allows for wider spacing within lower power ranges and closer spacing within higher power ranges, and individual power segments may be spaced further apart than adjacent segments, depending on specific circumstances.
2. Determining Installation Dimensions and the Correspondence between Power Rating and Installation Dimensions
The installation dimensions of a motor refer to the dimensions required for its installation with the associated machinery. It is crucial to determine the appropriate installation dimensions for a series of motors and the correspondence between power ratings and installation dimensions. The installation dimensions of a series of motors are generally graded according to the shaft center height. Their determination must comprehensively consider the specific circumstances of both the associated machinery and the motor itself, and should, in principle, increase sequentially according to a priority number system.
The main dimension consideration in installation is the shaft center height. For motors with end-cap bearings, determining the correspondence between power rating and installation dimensions primarily involves determining the correspondence between the power rating and the shaft center height. If too few shaft center height levels are selected after determining the power rating, while the manufacturing process equipment can be reduced and installation and use will be more convenient for users, the electromagnetic design will be less efficient, and materials will not be fully utilized. Therefore, this correspondence must be comprehensively considered, and multiple schemes must be calculated and compared. Typically, one shaft center height corresponds to two power ratings; in certain power ranges, it may also correspond to three power ratings.
3. Determination of the outer diameter of the stator laminations of AC series motors
When determining the outer diameter of the stator laminations for AC series motors, the following key factors should be considered: 1) Consistency with the specified shaft center height. Practice has shown that, when the shaft center height is constant, it is advisable to appropriately increase the outer diameter of the stator laminations if possible, as this is beneficial to both motor performance and manufacturability. 2) Economic rationality in utilizing silicon steel sheets. 3) Uniformity of the overall shape of the series; and, where conditions permit, full utilization of existing process equipment.
4. Standardization, serialization, and generalization of components
For a series of motor components, standard parts, dimensions, and structures should be used as much as possible. The dimensions of similar components should be rationally arranged according to the requirements of the entire series to improve versatility and interchangeability. For example, for AC motors, 2-3 specifications with the same number of poles and adjacent power ratings should use the same stator laminations (although the core lengths may differ). Motors with different numbers of poles and adjacent power ratings should preferably use the same stator lamination outer diameter, but different inner diameters, with the same or slightly different core lengths. For DC motors with different speeds but adjacent power ratings, the same armature outer diameter and pole laminations should be selected. This will greatly reduce the number of stamping dies and special dies, and further reduce the number of fixtures and measuring tools because the same shaft diameter, bearings, commutator, and winding supports can be used.
To ensure that the main dimensions of the motor are appropriate, for motors produced in large batches, the outer diameter of a core is generally limited to two core lengths, and occasionally three. For motors produced in smaller batches, more than two lengths can generally be used. Especially for high-power motors, when a welded frame is used, the change in length will not cause significant inconvenience in the process. Therefore, the core is sometimes made of three to four or more lengths.
5 Derivation Possibilities
In other words, we should consider the possibility that certain products can be derived with only minor modifications to meet the requirements of special performance, special environment and special use conditions.
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