Motor efficiency in ground source heat pump system
Good article source: "social channel" editor: Anhui electric motor
High efficiency motor problem
In ground source heat pump system used in all kinds of motor, according to the motor work efficiency can be divided into two categories: standard efficiency motor and high efficiency motor. Compared with the standard efficient motor motor efficiency, according to the different power, the efficiency can be increased 2 to 10 percentage points, high efficiency motor is of special materials and by employing better design can reduce the loss to achieve, but the price is about more than the standard motor efficiency 10%~30%, so the motor sold in the world only 1/5 is a high efficiency motor. The motor efficiency is the ratio of mechanical power output and input power, usually expressed as a percentage, is shown in Figure 1 between the standard motor and motor efficiency difference in unit consumption to produce more power consumption through efficient motor production improved design of materials and technology.
In general, high efficiency motors usually have a high load factor, better insulation and pressure, low heat and small vibration, thus increasing the reliability. High efficiency motor must have the equivalent or more than the United States International Electrical Manufacturing Industry Association (NEMA) of the general motor full load efficiency. In other words, a motor efficiency must be equal to or more than NEMA high efficiency motor full load efficiency values can be referred to as high efficiency motor. The cost of a high efficiency motor depends on the cost of the motor, the efficiency, the use of time, the cost of installation and maintenance, and labor costs. The extra cost of a high efficiency motor can be recovered by saving operating costs, quickly recover the cost, and usually the extra cost of the motor can be offset by the cost savings of two years. For example, assume that 50HP, load factor of 75% of the motor runs more than 4000H per year, electricity is $0.04/kWh, an improvement point can save 4079kwh or $163 per year. Therefore, a high efficiency motor, through the efficiency of 4%, two years more than the standard motor savings of $1304, basically meet the two year return standard.
Relationship between motor speed and load
Centrifugal pump and fan load is very sensitive to the speed change, speed only increased 5r/min can lead to a significant increase in flow rate and energy consumption, efficiency. So when replacing a pump or fan, you must select full load speed is equal to or lower than the speed of the motor is replaced. The power of the centrifugal motor driving the fan is proportional to the cube of the rotating speed. For example, if the motor speed increased from 1740r/min to 1760r/min, although only increased by 20r/min, but to increase the power consumption of 3.5%, while the amount of air or water will also change with the square of the speed. Slip speed and load dependent, it can make different motor driving the same load as possible, such as 100hp 25% motor output rated power, can be used instead of a 50HP or lower horsepower motor, but the power of 50HP is 50%, or 62.5% of 40hp, 83% of the motor 30HP, full load output 25hp. When the motor load is gradually increased, the speed will be reduced, the full speed full speed, therefore, Anhui electric motor that has low velocity and large load motor synchronous speed close to the operation, with full power to close less efficient motor synchronous speed, instead of large power but low speed the motor can significantly reduce operating costs.
