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Motor rotor



Motor rotor

Motor rotor: It is also a rotating part in a motor. The motor is composed of a rotor and a stator. It is used to realize the conversion device between electrical energy and mechanical energy and mechanical energy and electrical energy. The motor rotor is divided into a motor rotor and a generator rotor.

Rotation method

The motor rotor is divided into two types: inner rotor rotation and outer rotor rotation. The rotation mode of the inner rotor is that the core in the middle of the motor is a rotating body, outputting torque (referring to electric motor) or receiving energy (referring to generator). The rotation mode of the outer rotor is to use the outer body of the motor as the rotating body, and different modes facilitate the application in various occasions.

Brushless DC motor rotor

The rotor of the brushless DC motor is composed of permanent magnets with a certain number of pole pairs embedded on the surface of the iron core or embedded in the iron core. Permanent magnets are mostly made of rare earth permanent magnet materials with high coercivity and high permeability magnetic induction density such as neodymium iron boron. The role of the permanent magnet of this rotor is similar to that of the permanent magnet used in the brush motor, both of which establish a sufficient magnetic field in the air gap of the motor. The difference is that the permanent magnet in the brushless DC motor is installed in the rotor. Above, the magnet of the brushed motor is mounted on the stator. The rotor structure of the brushless DC motor mostly adopts surface-adhesive magnetic poles, also known as tile-shaped magnetic poles. The surface-adhesive magnetic pole is to paste a radially magnetized tile-based rare-earth permanent magnet on the outer surface of the iron core. A reasonable design can obtain the air gap magnetic flux density in the form of a square wave.

Rotor injection molding process

Put the metal insert into the mold, and then inject the BMC plastic. Heat to 160 degrees.

The power of the motor. It should be selected according to the power required by the production machinery, and try to make the motor run under the rated load. Pay attention to the following two points when selecting: (1) If the motor power is selected too small. There will be a "small horse-drawn cart" phenomenon, causing the electric motor to be overloaded for a long time. Make its insulation damaged by heat. Even the electric motor was burned. (2) If the motor power is selected too large. There will be a "big horse-drawn cart" phenomenon. The output mechanical power cannot be fully utilized, and the power factor and efficiency are not high (see table), which is not only detrimental to users and the power grid. It will also cause waste of electrical energy.

Motor power selection

To correctly select the power of the motor, the following calculation or comparison must be done: (1) For the constant load continuous working mode, if you know the power of the load (that is, the production machinery Power on the shaft) Pl (kw). The required motor power P(kw) can be calculated as follows: "P=P1/n1n2"" where n1 is the efficiency of the production machinery; n2 is the efficiency of the motor. That is transmission efficiency. The power calculated by the above formula is not necessarily the same as the product power. Therefore. The rated power of the selected motor should be equal to or slightly greater than the calculated power.

Example: The power of a production machine is 3.95kw. The mechanical efficiency is 70%. If a motor with an efficiency of 0.8 is selected, how much kw should the motor's power be? Solution: P=P1/n1n2=3.95/0.7*0.8=7.1kwBecause there is no 7.1kw— Specifications. So choose the electric motor of 7.5kw.

(2) Motors with short-time working quota. Compared with the continuous working rated motor of the same power. The maximum torque is large, the weight is small, and the price is low. Therefore, when conditions permit, a short-time rated motor should be used as much as possible.

(3) For the motor with intermittent work rating, the selection of its power should be based on the size of the load continuity rate, and the motor specially used for intermittent operation mode should be selected. The calculation formula of the load duration string Fs% is FS%=tg/(tg+to)×100% where tg is the working time, t. Is the stop time min; tg ten to is the working cycle time min.

In addition. The power of the motor can also be selected by analogy. The so-called analogy method. It is to compare with the power of motors used in similar production machinery. The specific method is: understand how much power motors are used in similar production machines in this unit or other nearby units, and then select motors of similar power for test runs. The purpose of the test run is to verify whether the selected motor matches the production machinery. The verification method is: make the motor drive the production machinery to run, measure the working current of the motor with a clamp ammeter, and compare the measured current with the rated current marked on the nameplate of the motor. If the actual working current of the electric power machine is not much different from the rated current marked on the Mingpi. It shows that the power of the selected motor is appropriate. If the actual working current of the motor is about 70% lower than the rated current marked on the nameplate. It indicates that the power of the motor is selected too large (that is, the "big horse-drawn trolley" should be replaced with a smaller power motor. If the measured working current of the motor is more than 40% larger than the rated current marked on the nameplate, it indicates the power of the motor If the selection is too small (ie "small horse-drawn cart"), the motor should be replaced with a larger power motor. table: load condition 1/4 load 1/2 load 3/4 load full load power factor 0.2 0.5 0.77 0.85 0.89 efficiency 0 0.78 0.85 0.88 0.895

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