The motor frame is a key structural component of the motor , significantly impacting its interchangeability and the uniformity of the air gap, and its machining is relatively complex. Therefore, the appropriate selection of the motor frame's machining scheme and method is crucial for improving motor quality and reducing machining costs. There are many types of motor frames, which can be categorized from various perspectives.
The machine base requires machining of the following parts: end faces, inner circles, base planes, base holes, fixed end covers, junction boxes, and bolt holes for hoisting. For split-type machine bases, the mating surfaces, mating bolt holes, and pin holes also need to be machined. The dimensional accuracy and surface roughness of each machined part of the machine base should conform to the specifications in the drawings. The end faces and inner circles require particularly high accuracy and surface roughness, and the center height must also be dimensionally accurate.
The form and position tolerances of all machined surfaces of the machine base should conform to the specifications in the drawings. The coaxiality of the end stops and inner circles, and the runout of the end faces facing the axis, are critical aspects of machine base machining and require special attention. If form and position tolerances are not specified, their maximum and minimum values should be within the dimensional tolerance range. Furthermore, the base plane should be parallel to the axis. The distance between the base feet and the machine base centerline should be symmetrical and conform to the specified tolerances.
After the magnetic base is machined, the thickness of all parts of the yoke should be uniform. The graduations of the magnetic pole holes should be equal, and their positions must conform to the drawings. The mating surfaces of the split base should be stably joined, reliably positioned, and able to meet the original requirements after disassembly and reassembly.
Types of base
●Magnetic properties. Based on whether the frame is magnetic, motors can be divided into magnetically conductive frames and non-magnetically conductive frames. Magnetically conductive frames are used for DC motors and pivot-type synchronous motors. Non-magnetically conductive frames are used for asynchronous motors, pole-rotating synchronous motors, and other motors with laminated stator cores (such as power amplifiers).
● Blank type. Based on the different blanks used for the machine base, it can be divided into welded machine bases and cast machine bases. Welded machine bases are made of welded steel. Cast machine bases can be made of cast steel, cast iron, or aluminum alloy. Magnetic guide machine bases almost always use a welded structure of cast steel or steel plates.
●Frame Material. Non-magnetic frames are generally made of gray cast iron. Cast iron frames are relatively inexpensive and easy to manufacture, and their mechanical strength is sufficient for the requirements of most small and medium-sized motors. Only in cases where high mechanical strength is required, such as explosion-proof motors and marine motors, are high-strength cast iron or cast steel frames used.
●Lightweight Alloys. In recent years, mass-produced small AC motors and micro motors have increasingly adopted frames made of die-cast aluminum-silicon alloys or aluminum-magnesium alloys. The advantage of this structure is that the aluminum alloy is directly cast onto the stator core, eliminating the need for machining the inner circle of the frame, saving on some fasteners, and also making the small motor lighter. Its disadvantages are that aluminum alloys are more expensive, have lower mechanical strength, and poorer wear resistance.
● Welded frame. Large motors with stator core outer diameters exceeding 1 meter, due to their low production volume and significant weight, commonly utilize welded frames made of shaped steel and steel plates. Compared to cast iron frames, welded frames are lighter while maintaining the same mechanical strength and structural rigidity. Welding eliminates the need for special molds, thus reducing costs and shortening the production cycle.
●Integral vs. Separate Types. Based on the different base structures, they can be divided into integral bases and separate bases. Integral bases are generally used. Separate bases have weaker structural rigidity and require more machining time. Their advantage is easier installation and maintenance.
Integrated motor bases are generally cylindrical with two or four feet at the bottom for motor mounting. Cylindrical bases offer the best manufacturability. However, for certain motors (such as traction motors) whose dimensions are limited by conditions (such as track gauge and shaft height), and where maximizing power is required, the base cross-section is often made polygonal to make full use of space. Polygonal bases are more complex to manufacture and increase processing costs.
●Other classification methods. For example, according to the different protection and cooling methods, the frame can be divided into open type, protective type, closed type, explosion-proof type, etc. The outer surface of closed type and explosion-proof type frames generally has heat sinks, while other frames do not. According to whether there are feet, they can be divided into frames with feet and frames without feet.
Disclaimer: This article is a reprint. If it involves copyright issues, please contact us promptly for deletion (QQ: 2737591964). We apologize for any inconvenience.
