Analysis on the causes of motor energy consumption and Its Solutions

Motor energy consumption performance is mainly in the following areas:

• First, the motor load rate is low. Due to improper motor selection, the affluent amount is too large or production process changes, making the actual working load of the motor is much smaller than the rated load, about 30% to 40% of the installed capacity of the motor operating at 30% to 50% of the rated load, operating efficiency is too low.
• Second, the power supply voltage is asymmetric or too low. Due to the unbalanced single-phase load of the three-phase four-wire low-voltage power supply system, the three-phase voltage of the motor is asymmetrical, and the motor generates negative sequence torque, increasing the three-phase voltage asymmetry of the motor, and the motor generates negative sequence torque, increasing the loss in the operation of the motor. In addition, the grid voltage is low for a long time, making the normal work of the motor current is large, and thus the loss increases, the greater the three-phase voltage asymmetry, the lower the voltage, the greater the loss.
• Third, the old, old (eliminated) type of motor is still in use. These motors use E-grade insulation, larger size, poor starting performance, low efficiency. Although experienced years of transformation, but there are still many places in use.
• Fourth, poor maintenance management. Some units of motors and equipment are not maintained in accordance with the requirements of maintenance, allowing them to run for a long time, making the loss increasing.

Therefore, for these energy-consuming performance, it is worth studying what kind of energy-saving programs to choose.

There are seven kinds of motor energy-saving programs

1. Choose energy-saving motor
Compared with ordinary motors, high-efficiency motors optimize the overall design, choose high-quality copper winding and silicon steel sheet, reduce various losses, the loss decreases by 20%~30%, and the efficiency increases by 2%~7%; the investment payback period is generally 1~2 years, some months. In comparison, the efficiency of high-efficiency motor is 0.413% higher than that of J02 series motor. Therefore, it is inevitable to replace the old motor with high efficiency motor.
2. Appropriate selection of motor capacity to achieve energy saving
The country has made the following regulations on the 3 operating areas of three-phase asynchronous motor: the load rate between 70% and 100% is the economic operating area; the load rate between 40% and 70% is the general operating area; the load rate below 40% is the non-economic operating area. Improper selection of motor capacity will undoubtedly cause waste of electric energy. Therefore, the use of suitable motor, improve the power factor, load factor, can reduce power loss and save electrical energy.
3. Adopt magnetic slot wedge instead of original slot wedge
Magnetic slot wedge mainly reduces the no-load iron loss in asynchronous motor. The no-load additional iron loss is generated in the stator and rotor cores by the harmonic flux caused by the tooth slot effect in the motor. The high frequency additional iron loss induced in the core by the stator and rotor is called pulsation loss. In addition, the stator and rotor teeth are sometimes right and sometimes wrong, and the flux of the tooth surface cluster changes, which can generate eddy currents in the tooth surface line layer and produce surface losses. Pulsation losses and surface losses are collectively called high frequency additional losses, which account for 70% to 90% of motor stray losses, and the other 10% to 30% are called load additional losses, which are generated by leakage flux. Although the use of magnetic slot wedge will reduce the starting torque by 10%~20%, the iron loss of the motor with magnetic slot wedge can be reduced by 60k than that of the motor with ordinary slot wedge, and it is very suitable for the transformation of the motor with no-load or light-load starting.

4. Adopt Y/△ automatic conversion device
In order to solve the waste of electric energy when the equipment is lightly loaded, Y/△ automatic conversion device can be used to achieve the purpose of power saving without replacing the motor. Because in the three-phase AC grid, the voltage obtained by different connections of the load is different, and thus the energy drawn from the grid is also different.
5. Power factor reactive power compensation of motor
Improve power factor, reduce power loss is the main purpose of reactive power compensation. Power factor is equal to the ratio of active power to apparent power, usually, low power factor will cause excessive current, for a given load, when the supply voltage is certain, then the lower the power factor, the higher the current. Therefore, the power factor is as high as possible to save power.
6. Inverter speed control
Most of the fan and water pump loads are selected according to the amount of full-load work required, and most of the time in the actual application is not in full-load working condition. Because of the AC motor speed control is very difficult, commonly used baffle, return valve or open and close time, to adjust the air volume or flow, while the large motor in the frequency state frequently open and close more difficult, the power impact is larger, is bound to cause power loss and open and close when the current impact. The use of inverter direct control of fan and pump loads is one of the most scientific control methods, when the motor is running at 80% of the rated speed, the energy-saving efficiency is close to 40%, while closed-loop constant voltage control can also be achieved, the energy-saving efficiency will be further improved. As the inverter can realize the soft stop and soft start of the large motor, avoiding the voltage shock when starting, reducing the motor failure rate and extending the service life, and also reducing the capacity requirements of the grid and reactive power loss.
7. Liquid speed control for wire-wound motor

Liquid resistance speed control technology is developed on the basis of the traditional product liquid resistance starter. Still change the pole plate spacing to adjust the size of the resistance to achieve the purpose of stepless speed regulation. This makes it have good starting performance at the same time, it is energized for a long time, bringing the problem of heating up, due to the adoption of a unique structure and reasonable heat exchange system, its working temperature is limited to a reasonable temperature below. Liquid resistance speed control technology for wirewound motors, with its reliable work, easy installation, energy saving, easy maintenance and low investment, has been rapidly promoted, for some speed control accuracy requirements are not high, speed range requirements are not wide, and infrequent speed control of wirewound motors, such as fans, pumps and other equipment of medium and large wirewound asynchronous motor using liquid speed control effect is significant.

Source: China Permanent Magnet Manufacturer – www.rizinia.com