The advantages and disadvantages of brushless AC motors and their maintenance cycles

Is the AC motor brushless or brushless?

There are two types of AC motors: brushed AC motors and brushless DC motors (also called brushless AC motors). So an AC motor may have brushes or it may be brushless.

Usually, AC motors are not classified by brush or brushless. However, some AC motors are brushless and some are brushless. Three-phase cage rotor AC motors are brushless, while three-phase wound rotor AC motors are brushless; single-phase motors with capacitors (such as electric fans) are brushless, and single-phase cage motors are also brushless; and single-phase general-purpose motors (such as hand drills and other power tools) are brushed. In addition, AC motors with external DC excitation power supplies are also brushed.

Advantages and disadvantages of AC motors

Advantages of AC motors:

1. High working efficiency. AC motors are generally more efficient than DC motors because they can utilize the variable frequency and phase difference of electrical energy.

2. Low maintenance cost. Since the AC motor has a simple structure and long service life, the maintenance cost is relatively low.

3. Smooth operation. AC motors have no rotating inertia when working, so they are more stable.

4. High reliability. AC motors have been developed for many years under the support of large-scale production and international standards, showing very high reliability and stability.

Disadvantages of AC motors:

1. Control is difficult. In order to control the AC motor, its frequency, phase and voltage need to be precisely controlled, which requires a more complex control circuit.

2. High initial cost. AC motors are more expensive to manufacture and control than DC motors.

3. Difficulty in maintenance. The internal circuit of AC motor is more complicated than that of DC motor, so it is relatively difficult to maintain.

AC motor maintenance cycle

The maintenance cycle of AC motors varies depending on factors such as model, load, and working environment. It is generally recommended to perform maintenance according to the following cycles:

1. Daily maintenance: Daily cleaning, inspection and lubrication should generally be performed every day or after each use.

2. Regular maintenance: Perform more thorough and in-depth maintenance on each component of the motor, including cleaning, lubrication, replacement of wearing parts, etc. It is generally recommended to perform this maintenance every 6 months.

3. Overhaul: Large-scale maintenance work such as repairing the motor and replacing parts is generally recommended to be carried out every 3-5 years.

The above cycle is for reference only. The actual maintenance work needs to be formulated according to the specific conditions of the motor and the working environment. At the same time, maintenance work should be performed by professionals to avoid equipment damage or safety accidents caused by incorrect operation.

The contents of regular maintenance are as follows.

1. Clean the motor. Remove dust and sludge from the outside of the motor base in time. If the environment is dusty, it is best to clean it once a day.

2. Check and clean the motor terminals. Check whether the terminal box screws are loose or burned.

3. Check the screws of each fixed part, including the anchor screws, end cover screws, bearing cover screws, etc. Tighten the loose nuts. 4. Check the transmission device, check whether the pulley or coupling is weak or damaged, whether the installation is firm, and whether the belt and its coupling buckle are intact.

5. The starting equipment of the motor should also be cleaned of external dust and dirt in time, the contacts should be wiped, and the wiring parts should be checked for signs of burns and whether the grounding wire is in good condition.

6. Inspection and maintenance of bearings. Bearings should be cleaned and lubricated with grease or oil after being used for a period of time. The time for cleaning and oil change should be determined by the working condition, working environment, cleanliness and type of lubricant of the motor. Half of the bearings should be cleaned and lubricated with grease every 3-6 months. When the oil temperature is high, or the environment is poor and there is a lot of dust, the motor should be cleaned and oiled frequently.

7. Check the insulation condition. The insulation capacity of the insulating material varies with the degree of dryness, so it is very important to check the dryness of the motor winding. The presence of factors such as a humid working environment of the motor and corrosive gases in the workplace will damage the electrical insulation. The most common is the winding grounding fault, that is, the insulation is damaged, causing the live parts to collide with the metal parts such as the casing that should not be charged. This kind of fault not only affects the normal operation of the motor, but also endangers personal safety. Therefore, when the motor is in use, the insulation resistance should be checked frequently, and attention should be paid to whether the motor casing is reliably grounded.

8. In addition to the regular maintenance of the motor according to the above items, an overhaul is required after one year of operation. The purpose of the overhaul is to conduct a thorough and comprehensive inspection and maintenance of the motor, add missing and worn components of the motor, completely eliminate dust and dirt inside and outside the motor, check the insulation, clean the bearings and check their wear. If problems are found, deal with them in time.