Motor frame type and its processing control requirements

Motor base type

According to whether the base is magnetic, it can be divided into magnetic and non-magnetic bases. Magnetically conductive machine bases are used for DC motors and rotating synchronous motors. Non-magnetic bearings are used for asynchronous motors, rotary-synchronous motors and other motors with laminated stator cores.


● According to the difference of machine base blanks, it can be divided into welding and casting bases. The welding base is welded from steel. Foundry bases can be cast from cast steel, cast iron or aluminum alloys; almost all magnetically conductive machine bases are cast steel or steel plate welded structures.

● Non-magnetic holders are generally made of gray cast iron. The cast iron base is low in cost and easy to process. Its mechanical strength can meet the requirements of general small and medium-sized motors. Only in the case of high mechanical strength requirements, such as explosion-proof motors and marine motors, high-strength cast iron or cast steel stands are used.

Small-sized AC motors and micro-motors have gradually been cast in aluminum-silicon alloy or aluminum-magnesium alloy die-casting bases in recent years. The feature of this structure is that the aluminum alloy can be directly cast on the stator core, the inner circle of the base does not need to be processed, some fasteners are omitted, and the small motor can be made lightweight. The disadvantage is that the aluminum alloy material has a high price, a weak mechanical strength, and a poor wear resistance.

● For large motors, steel and steel plate welding bases have been widely used because of small output and large motor weight. Compared with the cast iron frame, the weight of the welded frame is lighter under the same mechanical strength and structural rigidity. When welding, no special mold is required. Relatively speaking, the cost is lower, the production cycle can be shortened, and the requirements for the personalized shape of the motor can also be satisfied.

According to the different structure of the base, it can be divided into an integral base and a separate base.


Separation bases have weaker structural rigidity and more processing man-hours. Improper assembly can also cause the complete machine to fail to meet the requirements. However, its unique advantages are the ease of installation and maintenance. When the design is reasonable, problems such as assembly accuracy and structural rigidity are no longer the limiting factors.

Integral type seats are relatively large and the section is generally designed to be cylindrical. There are two or four feet in the lower part of the base, and the power supply machine is installed and used. Cylindrical stands have the best processability, but for some motors, when the dimensions are limited by certain conditions and power is required to be increased as much as possible, the cross section of the stand is often designed as a polygon to make full use of the space. Polygonal seats are more complex to manufacture and processing costs increase.

Other classification methods. According to the different protection and cooling methods, the base can be divided into open type, protective type, closed type and explosion-proof type. The outer surfaces of enclosed and explosion-proof bases are usually equipped with heat sinks, while other bases are not equipped with heat sinks. According to whether there are feet or feet, it can be divided into bases with foot (such as B3 and B35) and without feet (such as V1 and B5).

Seat processing technical requirements

The parts that need to be machined in the frame mainly include the two-end spigot, the end face, the inner circle, the bottom foot plane, the foot hole, the fixed end cap, the outlet box, and the lifting bolts. For a separate stand, it is also necessary to machine the mating face, split screw holes, and pin holes. The technical requirements that should be met during the machining of the base can basically be summarized as the following.


● The dimensional accuracy and roughness of each processing site should comply with the drawings. The accuracy and roughness requirements of both end-end and inner circles are both high, and the center's high dimensional accuracy is also accurate.

● The geometrical tolerance of each processing surface shall comply with the drawings. The concentricity of the end-end and inner circle at both ends and the face-to-face runout of the two ends facing the axis line are the key to the machining of the machine base. Special emphasis: If the geometric tolerance is not specified, the maximum and minimum values should be within the dimensional tolerance range; the foot plane should be parallel to the axis line.

● The distance between the foot hole and the centerline of the stand should be symmetrical, and meet the specified tolerances.

● The thickness of each part of the yoke should be uniform after machining of the magnetically conductive machine base. The pole hole index should be equal and its position must be in accordance with the drawings.

● The split plane of the separation base requires stable joints, reliable positioning, and can still meet the original requirements when reassembled.