How to determine the main size of the motor?
Today I will talk to you about the general method of determining the main dimensions of the motor. Some motors may take different steps according to their own characteristics, and even write the main dimensional relationship into other forms.
1 Calculate the power P,
First, the calculated power P is obtained by using equations (1)-(5) according to the rated power of the motor.
Then according to P, and n (AC motor is synchronous speed, DC motor is rated speed), combined with the characteristics of the designed motor, using the recommended data or curve to select the electromagnetic load A, Bδ, substituting (6) can be calculated motor Armature volume D2Lef.
2 D and Lef calculation
The main dimensions D and Lef can be obtained from the calculated armature volume D2Lef by selecting the appropriate λ with reference to the recommended data. For asynchronous and synchronous motors, also determine their stator outer diameter D1. In order to make full use of silicon steel sheets, reduce the specifications and quantity of process equipment such as die, strengthen the versatility and consider the need of increasing power levels of series motors, China currently stipulates the standard outer diameter D1 of AC motor stator core and the standard armature of DC motor. Trail Da. When D1 (or Da) > 99 cm, a fan-shaped piece should be used.
It should be pointed out that the standard diameters specified are not in accordance with the current production level regulations in China. In fact, other diameters are also used in some new series of motors.
3 empirical analogy
In actual production, due to the accumulated rich practical experience, the “analog method” is often used to determine the main dimensions. The so-called "analog method" is based on the specific conditions (structure, materials, technical and economic indicators, processes, etc.) of the designed motor, and refers to the design and test data of the similarly-sized motors of the same type that have been produced, directly selecting the main dimensions and some Other data. For example, for asynchronous motors, the "outer analog" is usually used to directly select the outer diameter of the stator (and the corresponding frame number or shaft center height), the inner diameter, the length and the air gap size, the rotor inner diameter, the number of stator slots, and the like. If the designed motor I and the same type of motor II that have been produced have the same number of poles and different rated powers, it is known from equation (6) that the armature length, conductor cross section and number of turns can be approximated by the relationship of PNI/PNII. .
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