Compared with synchronous motors, asynchronous motors have lower manufacturing costs (15%-25% lower) and longer service life (about 18 years, 20% longer than synchronous motors). They have a low failure rate and reduce maintenance costs by 20%-30%. High-efficiency asynchronous motors can save 10%-15% of energy in industrial applications and adapt to various load fluctuations.
Simple structure
Asynchronous motors are usually manufactured at a cost of 15% to 25% lower compared to synchronous motors. For example, for a 1 kW motor, the price of an asynchronous motor is around 70% of that of a synchronous motor.
The failure rate of equipment using asynchronous motors is 30%-40% lower than that of equipment using synchronous motors. The asynchronous motor used has been running continuously for more than 2,000 hours without a single failure, while the number of failures of equipment using synchronous motors in the same period reached 2 times.
The highest efficiency in some high-efficiency asynchronous motors can be more than 90%, and a certain type of three-phase asynchronous motor reaches 95% when operating under full load.
More than 70% of motors used in industrial fields are asynchronous motors. A 75 kW asynchronous motor can work continuously and stably in mining areas with an ambient temperature of more than 40 degrees Celsius, and its service life is usually more than 15 years.
The average life of an asynchronous motor is about 18 years, which, compared with an average of 15 years’ service life of a synchronous motor used in the same period, extends the service life of an asynchronous motor by more than 20% over that of a synchronous motor.
Many modern asynchronous motors use efficient and energy-saving designs, which reduce the energy consumption of such motors by approximately 10%-15%. Energy consumption has been reduced by 13% in certain fan systems using some of the improved asynchronous motors.
An asynchronous motor with a power of 11 kW weighs about 90 kg.
Asynchronous motors are more space-saving because of their compact design. Even some smaller asynchronous motors can be put into equipment housings up to 2 meters high.
Low maintenance cost
The maintenance cost of asynchronous motors is usually 20%-30% lower than that of synchronous motors. In high-load and high-temperature environments, equipment using asynchronous motors have nearly 40% fewer repairs compared with synchronous motors.
The maintenance cost of an asynchronous three-phase motor is about RMB 150,000 annually in a power plant. Repair and replacement of parts of the synchronous motor of the same power involves RMB 240,000. Thus, the maintenance cost of asynchronous motors is RMB 90,000 less than synchronous motors.
The failure rate of equipment for asynchronous motors stands at 2%-3% per year and for synchronous motor, it’s up to 5%-6%.
The general service life for pumps driven with asynchronous motors would be more than 10 years, while those using traditional brush motors would only serve for 5 to 6 years.
Asynchronous motors can normally operate continuously for 24 hours in a transmission system of steel plants. Their maintenance needs occur 2-3 times a year, whereas the other type of motors will need 4-5 times. Elevator systems with asynchronous motors can generally be operated without major maintenance over a period of 1-2 years.
The use of asynchronous motors can drastically minimize the requirement of skilled maintenance people and hence decrease training and labor costs.
In the whole life cycle, the number of parts to be replaced by asynchronous motors is only 60%-70% of that by synchronous motors. Within a 10-year service life, the asynchronous motors’ parts to be replaced may only account for 30% of the total maintenance cost, while most synchronous motors’ parts often cost more than 50% of the total cost.
Asynchronous motors with intelligent monitoring systems reduce maintenance costs by around 10%-15%.
Reliable operation
The mean time between failures of asynchronous motors is usually above 3,000 hours, while that of synchronous motors is around 2,500 hours.
A large steel plant uses asynchronous motors to drive large conveyors and crushers, which run 24 hours a day. After 5 years of operation, these asynchronous motors have only had 1 failure, with an average failure rate of 0.2%, while the failure rate of synchronous motors used in the same period was 0.6%.
A ventilation system driven by asynchronous motors in an underground mining environment of a mine in the north has been stably running for more than 15 years.
Even with strong fluctuations in large loads, asynchronous motors can still achieve operating efficiency greater than 90%.
In a high electromagnetic interference environment, the stability of asynchronous motors is much better than that of synchronous motors.
The asynchronous motors will be able to run continuously and stably in high temperatures, even above 40°C. The asynchronous motors used in the offshore oil platform can operate continuously for over 2,000 hours in a very humid offshore environment.
Usually, the asynchronous motors that can be used in wind turbines have more than 5 years’ continuous operation. In some projects of wind power investments, the asynchronous motor’s annual maintenance cost only makes for 2%-3% of the total investment in equipment, while the average annual maintenance cost of other kinds of motors during the same time is usually between 4% and 6%. The operation control system of the asynchronous motors is relatively simple. Thus, it is more convenient to conduct debugging and maintenance.
Adaptable to various industrial applications
Asynchronous motors occupied about 70% of the market share and became the first choice of power drive method in many industrial fields.
About 80% of mining equipment uses asynchronous motors. Mining equipment using asynchronous motors has a failure rate that is 20%-30% lower than other types of motors in the same period.
About 60% of wind turbines in the world use asynchronous motors. The asynchronous motors of a certain wind power project have been running for more than 7 years and have not had a major failure so far. In the water pump system, the operating efficiency of asynchronous motors remains above 85%. More than 70% of steel production lines use asynchronous motor drive systems.
Asynchronous motors are used as the most important driving power in about 65% of chemical plants. Asynchronous motor drive systems are employed in about 72% of textile mills and 65% of paper mills.
Asynchronous motors are used in more than 50% of water treatment plants. The asynchronous motors can ensure stable performance for 24-hour operation without interruption. About 80% of electrified railway systems use asynchronous motors as traction systems.
The annual maintenance costs of the production lines using asynchronous motors in the food processing industry are estimated to be 30%-40% less than those by the production lines employing synchronous motors.
High efficiency
High-efficiency modern asynchronous motors have the efficiency as a rule over 90%, by 5%-8% higher than the old one. Improving energy efficiency of asynchronous motors in a large steel plant saved the plant nearly 2 million yuan in electricity per year. The sum saved means 1.5% of all the annual operating cost.
Most wind turbines are made with asynchronous motors, and their efficiency often ranges from over 93% to 95%. In a wind power generation project, the utilization of high-efficiency asynchronous motors reduced the cost of electricity production by almost 10%, and the rate of return for the project increased by 15%.
In a water treatment plant, the pump system driven by asynchronous motors yields efficiency over 95%, and traditional synchronous motors would only yield an efficiency of around 90%. Therefore, it was possible to save more than 300,000 yuan in electricity costs per year with this pump system using high-efficiency asynchronous motors, and the investment payback period for the motor was only around 3 years.
The asynchronous motor’s efficiency-fluctuation range is usually maintained within 1%-2% when the load fluctuates. In the same environment, the fluctuation of efficiency for synchronous motors may reach up to 3%-5%.
By using the steel production electric roller as an example, after taking asynchronous motors into use, energy efficiency of equipment increased by over 8%, and the average annual cost savings on electricity has reached as high as 1 million yuan.
A fan system using asynchronous motors can consume around 15%-20% less power compared with the conventional air-conditioning system in a big commercial building.
Low energy consumption
It is possible for the asynchronous motor to have as much as over 90% in energy efficiency, while the improvement usually falls between 5%-10% for asynchronous motors. After a chemical plant installed new asynchronous motors in place of old ones, the annual average power consumption decreased by about 2 million kWh, thus saving more than 1.5 million yuan on electricity bills.
The wind turbines using double-fed asynchronous motors are generally around 92%-95% of energy efficiency. Using asynchronous motors, an offshore wind farm will save around 200,000 kWh of electricity consumption per year and the reduced cost from electricity consumption close to 1 million yuan.
The efficiency of asynchronous motors could be about 90% in a typical mine hoisting system. The annual average power consumption of equipment was reduced by 15%-20% and more than 500,000 yuan of electricity bill was saved yearly.
After using asynchronous motors, the overall energy efficiency of the production line has increased by more than 10%, and the average annual electricity cost savings have reached 800,000 yuan.
Strong overload capacity
Asynchronous motors remain stable for some time when loads are more than rated values; they can accept an overload, usually 1.5-2 times the rated load.
After applying asynchronous motors, the overload capacity of equipment in the metallurgical industry under high load is already 2 times the rated load.
Since it adopted an asynchronous motor air-conditioning system, a large commercial building has reduced the system load fluctuations that hit the motor by 50%.
Asynchronous motors can generally tolerate a load between 150%-200% of the rated load for a period of 1-5 minutes. The reactor driven by an asynchronous motor can tolerate a load of 200% in a short period of time. The maximum current that an asynchronous motor can tolerate during the starting process is 6 times the rated current.
