Motors, commonly referred to as electric motors, are devices that convert electrical energy into mechanical motion. They play a crucial role in industrial and commercial applications by utilizing the electricity generated by generators for various production processes. The basic structure of a motor is similar to that of a generator, but their operating principles are opposite: while a generator produces electricity through the movement of a rotor in a magnetic field, a motor uses electrical current to generate motion in its rotor. To create a strong magnetic field, both motors and generators typically use electromagnets.
**Motor Structure**
A three-phase asynchronous motor consists of two main parts: the stator and the rotor. The stator, which remains stationary, includes the motor housing, three sets of windings, and silicon steel laminations. The rotor, on the other hand, is the rotating component that contains the rotor core with embedded coils. Bearings at both ends of the shaft support the rotor, and the inner bearing cap holds the lubricating oil, while the outer cap prevents misalignment and leakage. Additionally, the motor has blades at the end, secured with snap rings for stability.
**Motor Maintenance Methods**
Proper maintenance is essential to ensure the longevity and efficiency of a motor. A professional maintenance process typically involves cleaning the rotor, replacing worn components like carbon brushes, performing vacuum pressure impregnation with insulation paint, drying, and balancing the rotor. Regular checks should be conducted to maintain optimal performance.
1. Keep the motor’s environment dry and clean, ensuring that air vents are not blocked by dust or fibers.
2. If the motor’s thermal protection keeps tripping, investigate whether the issue stems from overload or incorrect settings. Resolve the fault before restarting.
3. Ensure proper lubrication of bearings. After 5,000 hours of operation, grease should be replaced or replenished. Clean old oil with gasoline, then fill the bearing cavity with ZL-3 lithium-based grease up to 1/2 for 2-pole motors and 2/3 for 4, 6, and 8-pole motors.
4. When the motor’s bearings show increased vibration or noise, it may be time for replacement. Check radial clearance and replace the bearings if necessary.
5. During disassembly, carefully remove the rotor from the non-extended end to avoid damaging the stator windings.
6. When replacing windings, document all original specifications, such as winding type, wire gauge, and number of turns. Avoid altering the design without manufacturer approval, as this can lead to performance issues or failure.
**Motor Wiring Inspection**
Whether it's an AC or DC motor, the windings are usually separated and connected to external circuits according to specific requirements. This process, known as motor wiring, is critical during installation. Before connecting the wires, review the wiring diagram provided in the motor’s junction box. Proper wiring ensures safe and efficient operation.
For DC motors, the wiring diagram is often marked on the junction box cover, allowing selection based on excitation type and load direction. While reversing the phase in AC motors won’t damage the motor, DC motors require careful handling. Reversing the armature and field windings improperly can cause serious issues, such as uncontrolled rotation or overheating. Always double-check connections before powering up.
Before connecting the motor to the power supply, inspect the terminal connections for looseness. Tighten the internal lead wires and connect the shorting piece according to the required configuration. It is also important to test the motor’s insulation resistance using a megohmmeter (at 500V) to ensure it exceeds 0.5 MΩ. Once everything is set, perform a full system check before commissioning:
1. Civil engineering work should be complete.
2. Motor installation and inspection must be finalized.
3. Secondary circuit testing, including control systems, should be completed.
4. Rotor movement should be smooth without any jamming.
5. All main circuit wiring must be securely fastened.
6. Other associated systems should be fully operational.
Among these, the fifth point is especially important. The main circuit includes all wiring from the power distribution panel to the motor terminals. Every connection—such as switches, contactors, fuses, and thermal relays—must be tight and secure to prevent potential failures or damage.
During trial operation, monitor the motor’s current and record it. Also, verify the direction of rotation, listen for unusual noises, and ensure the motor runs smoothly without any abnormal sounds. These steps help ensure the motor operates safely and efficiently over its lifespan.
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