Today we will talk about the relationship between electric motor speed and electrical motor efficiency.
Does the electric motor with high efficiency necessarily have a fast speed?
Electric motor Efficiency is an important performance indicator of electrical motor products.
especially under the guidance of the national electrical energy saving and emission reduction policy, energy-efficient motors have been gradually accepted by customers.
Energy efficiency limits for a large number of induction motors have bound and standardized electric motor manufacturers to guarantee the efficiency of motors.
Third-party product energy efficiency certification activities, for the standardization of manufacturers of product level assurance capabilities to support the evidence.
For electric motors with different numbers of poles, the motor's efficiency indexes are assessed differently, and the efficiency indexes of high speed electrial motors are higher than those of low speed electric motors.
The graph below shows the limits of the efficiency indicators for motors with different poles but the same power in some of the power sections in GB/T32891.1.
In addition to 2-pole motors, the lower the speed of 4, 6 and 8-pole synchronous motor, the lower the efficiency.
Under the same power conditions, the speed and torque are negatively correlated, i.e. the higher the speed the lower the torque.
From the data in the table above we can see that the electrical motor efficiency of the 2P induction motor is lower than that of the 4P induction motor.
This is directly related to the relatively large size of the stator winding ends of 2P motors.
The fact that the winding span of the 2P induction motor is larger and the inlay process, which predestines the winding ends to be longer, naturally increases the copper losses of the motor.
If you understand the function and role of the winding ends, we know that theoretically the smaller the end size the better the peak efficiency level of the motor.
However, the higher the speed, the higher the efficiency quality for the same torque induction motor.
This is the inevitable result of the high material utilisation rate of high speed asynchronous motors and the tendency to reduce the heat losses consumed in the material.
The turndown rate is an important parameter specific to asynchronous motors
It is also a barometer of their optimal efficiency.
Comparing the speed of a high-efficiency motor with that of an ordinary motor, we can see that the speed of a high-efficiency electrial motor is higher than that of an ordinary motor, or that the turndown rate is smaller.
Because of the motor turndown rate and rotor winding resistance is closely related, resistance, turndown rate is large, rotor resistance loss is also large, resulting in low efficiency value. A typical example of a low turndown and high efficiency classes is the patented technology of replacing cast aluminium rotors with cast copper rotors in ultra-super-efficient motors.
When it comes to the speed of the first industrial electric motor, we naturally think about how the efficiency of the copper wire motor goes in different frequency states.
Taking the more common 50Hz and 60Hz motors as an example, how does the efficiency of the electrical motor actually vary with frequency, given the same electric power and torque?
In small to medium sized asynchronous motors, winding losses are the mainstay.
When the torque remains constant, the current flowing through the winding does not change significantly due to an increase in the supply frequency (from 50 Hz to 60 Hz).
Although wind turbulence and iron consumption increase with increasing frequency, in electrical motors with 4 poles and above wind turbulence and iron consumption account for a smaller proportion, much less than the increase in power, and the general trend of increasing efficiency values is constant.
When the frequency increases to a certain level, the core loss increases dramatically and the wind turbulence also increases significantly, the motor load efficiencies will shift to a trend of decreasing with increasing frequency.
Efficiency indicators relate to the economy of electrical motor operation.
In order to improve the human living environment, regions around the world have imposed minimum energy efficiency limits on the efficiency of motors applied to their region.
China has introduced many incentives for the application of high-efficiency and ultra-super-efficient motors for system energy efficiency.
The application of variable speed permanent magnet motors with high power density and wide speed range on new energy vehicles can be subsidised by national policy on the one hand, and more importantly by the consideration of energy efficiency or the hard target of range.
With the promotion and deepening of the application of high-efficiency motors, the simple improvement of induction motors performance is far from being able to solve the requirements of improving the operating efficiency of equipment.
The integration of motors into the supporting equipment for integrated design and control has become an inevitable trend.
Renew and eliminate high energy-consuming industrial electric motor and equipment, scientifically and rationally match the power system.
It apply low-speed direct drive technology, simplify the reduction mechanism and the corresponding series of auxiliary facilities, and significantly improve the operating efficiency of the system; vigorously promote frequency-controlled motors.
It make full use of technical measures such as soft start, reactive power compensation and intelligent power configuration to continuously improve the level and effectiveness of energy saving and efficiency.
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