Selection of small AC motors is a comprehensive consideration process involving many factors. The following is a systematic introduction of the relevant knowledge from several aspects, including motor characteristics, motor parameters, price and quality, installation and maintenance.
A. Motor Characteristics
a) Load Characteristics
According to the nature of the load of the machine and the production process, the starting, braking, reversing, speed regulation and other requirements of the motor, the type of motor is reasonably selected. For example, loads requiring frequent starting should use motors with large starting torque and good starting performance; while industries such as textile should choose torque motors with uniform and consistent pulling force. (For more information about torque motors, please click the link )
b) Overload capacity
Consider the motor's temperature rise limit and overload capacity to ensure that the motor will remain stable during long periods of operation or short periods of overload.
B. Motor Parameters
a) Output power
Select the appropriate motor according to the usage scenario and power demand, too big or too small will affect the usage effect. For example, to drive a small fan, the power does not need to be too large; but if you drive a small machine tool, the power requirement will be higher, otherwise the motor will not be able to carry the equipment. Calculate the power, take into account the load torque and speed of the equipment, power (P) = torque (T) × speed (n) / 9550 (units are kilowatts, N - m, rpm). It is necessary to determine the required power by calculation or analogical method, and select a motor model slightly greater than or equal to the required power.
b) Speed
According to the use of demand to select the appropriate speed, too high or too low are not conducive to the service life of the motor. Like washing machine motors, the speed is required to be able to change according to the different stages of the washing program; while the speed of electric fan motors is generally more fixed to match the design of the fan blades, too high a speed may produce noise and safety problems, too low and can not produce enough air volume.
c) Rated voltage
The rated voltage of the motor should be taken into account when selecting a model, and a motor with a power supply voltage that is the same or similar to the rated voltage of the motor should be selected. This helps to ensure stable operation of the motor under rated conditions and avoids failures caused by voltage mismatch. Common small AC motor voltages are 220 V and 380 V. Choose according to the supply voltage of the place where you are. If it is a domestic environment, it is usually 220V; both voltages may be used in industrial environments.
d) Current
When selecting a motor, it is also necessary to consider its rated current and maximum current to ensure that the motor will not exceed its current carrying capacity during operation.
e) Frequency
China's grid frequency is 50Hz, so most small AC motors are designed for 50Hz power. However, there are countries where the grid frequency is 60Hz, so you should pay attention to whether the frequency is suitable when you are purchasing. However, there are some special purpose motors that can work under other frequencies, when choosing, make sure that the rated frequency of the motor and the power supply frequency is the same.
f) Protection level
According to the environmental conditions of the place of use (e.g. temperature, humidity, dust, rain, gas, corrosive and explosive gas content, etc.), consider the necessary protection methods, and select the protective structure type of the motor. For example, “IP23” motors are suitable for dry and clean places, while “IP44” motors have higher protection levels.
g) Structure
Small motors have a variety of structural forms, such as open, protective, closed, sealed, explosion-proof and so on. According to the use of environment and installation space to choose the appropriate form of structure. For example, in a humid, corrosive dusty environment, closed motors should be used.
h) Insulation level
The insulation level of the motor determines the safe, stable and continuous operation of the motor under what kind of ambient temperature. Common insulation classes are A, E, B, F, H and so on. (To learn more about insulation ratings click on the link)
C. Price and Quality of Motors
a) Price
Under the premise of meeting the performance requirements, the motor model with reasonable price should be selected as far as possible to reduce the initial investment cost. At the same time, the running cost and maintenance cost of the motor should also be considered.
b) Quality
The quality of the motor is directly related to its service life and reliability. When selecting, priority should be given to motor brands with reliable quality and stable performance.
D. Motor Installation and Maintenance
a) Mounting form
The mounting form of the motor should be selected according to the way the motor is installed in the production machinery. In general, the horizontal type is preferred, while the vertical type is more expensive and is used only to simplify the transmission and when vertical operation is necessary.
b) Convenience of maintenance
When selecting a motor, it is also necessary to consider the ease of maintenance. For example, easy to disassemble and clean the motor structure helps to reduce the difficulty and cost of maintenance.
In summary, the selection of small AC motors need to comprehensively consider the mechanical characteristics, power and speed, voltage and current, structural form and level of protection, quality and price, as well as installation and maintenance and other aspects. Through scientific and reasonable selection, can ensure that the motor in the operation process to maintain stable, efficient and reliable performance.