How to deal with temperature rise and fall of AC motor

Due to ohmic heat losses, frictional heat losses, magnetization and eddy current losses, they eventually translate into heat losses with increased disordered entropy, causing the motor to increase in temperature during normal operation. Obviously, the greater the power, the greater the losses, so the allowable temperature corresponds to the maximum motor power. Excessive temperatures can threaten winding insulation and shorten the life of the motor. The decisive factor affecting the temperature rise of the motor is the permanent high load, because the temperature rise in a short time depends on the specific heat capacity, while the temperature rise in steady-state operation is determined by the cooling method and cooling effect. For temperature rise, there are three most important modes of operation:Constant operation: Continuous constant load condition, at least to bring the motor to thermal steady state. Short-time operation: The constant load duration is not sufficient for the motor to reach thermal stability. Intermittent work: intermittent constant load, motor temperature rise oscillation

Here is the list

How the motor is cooled during normal operation

Protection class of AC motor

How the motor is cooled during normal operation

The cooling method of the motor during normal operation is as follows: Natural ventilation: no fan is used, only air convection and radiation dissipate heat. Self-cooling: Cooling by fan blades mounted on the rotor. External cooling : A cooling device that is moved externally, e.g. a fan that is not mounted on the motor shaft. Through-hole ventilation (Durchzugbelüftung): The fan uses the cooling air that blows through the whole machine to dissipate heat. Surface Cooling: Dissipates heat through cooling devices attached to the surface of the enclosed motor. Circulating cooling: The medium coolant (such as liquid, gas) is repeatedly circulated for heat conduction and heat dissipation. Depending on the type of insulating layer and impregnating agent, a thermal class (Wärmeklassen) is also given. Different materials allow different maximum temperature rises and are therefore differentiated by thermal ratings.

Protection class of AC motor

The degree of protection (IP-Schutzarten) of AC motors follows a set of international standards (Ingress Protection, IP), which is a standardized classification of the degree of protection against the ingress of external water, dust and foreign objects. The critical motor protection class depends on the installation environment and the corresponding operating conditions:

IP23: The protection level is only for fingers and medium-sized foreign objects, and it is harmless to rain within 60 degrees in the vertical direction. This rating generally applies to internally cooled motors that must operate in a clean, dry environment.

IP44: Protection class For fingers and workpieces, granular foreign objects larger than 1mm are sputtered by water in any direction. Typically used for surface-cooled motors, which can work in harsh environments.

IP54, 55: Completely prevent foreign body intrusion. Although the intrusion of dust cannot be completely prevented, the amount of intrusion of dust will not affect normal operation and prevent the intrusion of water spray. It can work in very harsh wet and even chemically aggressive environments.

generalize

This chapter introduces the general situation, basic structure, stator, phasor representation, motor standardization, working mode, temperature rise and protection level of AC motors different from DC motors. AC Motor - Theory of Rotating Magnetic Fields.

Hangzhou New Hengli Electric Machine MFG. Co., Ltd.  works has been named the provincial advanced enterprise by Zhejiang provincial government and become a state grade-2 enterprise in 1988. Our motor max-power reaches 15000kW (A.C. motor), 2800kW (D.C. motor), and max-center-high dimension of our motor reaches 1250mm.