light industry

一、summary
In recent years, China's economy sustained rapid development, energy issues become more and more become industry development Zhi elbow, and with the rapid rise in energy prices, the domestic market fierce competition, energy saving has become the main problems faced by many industries, especially some large energy consumption industries such as petroleum, chemical, pharmaceutical, metallurgy, manufacturing, environmental protection, municipal and other industries. According to the information shows that China's high and low voltage motor, with a total capacity of above 35000MW, most for fan and pump load. Most of them work in the high energy consumption and low efficiency.
General fan, water pump system mostly depends on the valve to regulate the water flow or pressure and baffle the adjustment way is to increase the network loss and consumes a lot of energy to the price, therefore, inevitably cause waste of electric energy. And due to the design of the system is according to the maximum design load, in actual operation, the vast most of the system is not likely to run under full load condition, there is a large surplus, so there is great potential for energy saving.
ECF500 frequency conversion speed control device, by changing the speed of the fan, thereby changing the air flow in order to adapt to the needs of the production process, but also the most efficient operation of the province, the highest overall efficiency. So the variable frequency speed regulation is the best speed control scheme, it can realize the stepless speed regulation of the fan, and can be convenient to form a closed loop control system, realize constant pressure or constant flow control.

二、Energy saving analysis of Frequency Conversion Retrofit (taking fan as an example)
1, variable frequency speed regulation energy saving principle
According to the principle of fluid mechanics, the relationship between the wind turbine driven by the induction motor and the P of the shaft power Q and the wind pressure H:
P / Q*H when the motor speed varies from N1 to N2, Q, H, P the following relationship with speed:

Visible air volume Q and motor speed n is proportional to the relationship, and the required shaft power P and speed of the cubic proportional relationship. So when you need 80% of the rated air flow through the adjustment of the motor speed to 80% of the rated speed, that is, to adjust the frequency to 40.00Hz can be, when the required power will be only 51.2% of the original.
As shown in figure (1), the energy saving effect of frequency conversion speed regulation is analyzed from the operating curve of fan.

 When the required air volume reduced from Q1 to Q2, if we adopt the way of regulating damper, pipe resistance will be increased, pipeline characteristic curve upward, system operating points from point a to the new operating point B operation, the shaft power P2 and the area of H2 * Q2 is proportional to; if the use of speed control mode, the wind speed of the machine by N1 decreased to N2, the characteristics of the pipe network is not changed, but fan characteristic curve moves down by the, so the operating condition by a point to point C. At this time, the required axis power P3 is proportional to the area of HB * Q2. Theoretically analyzed, the savings of the shaft power Delt (P) and (H2-HB) x (C-B) is proportional to the area.
Taking into account the efficiency of the reduction and speed adjustment of the additional loss of the device, through the practice of statistics, the wind turbine speed control can be energy saving up to 20% ~ 50%.
2, frequency conversion energy saving analysis
Before the transformation of power frequency operation calculation formula of P1=U * I * 1.732 * COS phi, which:
U - motor voltage, kV; I - motor current, A; P1 - a single load under the power of the power frequency, kW;
With COS - load operation and single power factor, less than the rated power factor.
C1=T (P1 * * sigma delta), which:
T - annual average running time, h; P1 -- the running power under a single load, kW;
Delta -- the proportion of the full year run time under this load; C1 -- the total electricity consumption before the transformation, kW.h.
The estimated power calculation formula of the frequency conversion operation after transformation:

3、Energy saving control table: comparison of energy consumption of fan and water pump frequency conversion speed regulation

speed n%	flow Q%	wind pressure H%	Shaft power P%	Power saving rate%
100	100	100	100	0
90	90	81	72.9	27.1
80	80	64	51.2	48.8
70	70	49	34.3	65.7
60	60	36	21.6	78.4
50	50	25	12.5	87.5

The percentage and 100% of all traffic rated flow fan, power 100% rated power frequency operation consumption power (i.e. the motor input power = fan rated shaft power and efficiency of the motor, motor efficiency is 93 ~ 96%, the rated power greater efficiency is higher. The energy saving of frequency conversion timing is the difference of the energy consumption of the two regulating modes (the percentage is multiplied by the rated power consumption).

三、Other additional benefits of variable frequency speed regulation
(1) the grid side power factor improvement: the original motor directly driven by the power frequency, when the full load power factor of 0.85, the actual operating power factor is much lower than 0.8. Using variable frequency speed regulation system, the power factor of the power supply side can be increased to more than 0.9, without reactive power compensation device can greatly reduce reactive power and meet the requirements of power grid can be further upstream equipment operating cost savings.
(2) equipment operation and maintenance cost was decreased by variable frequency regulation, by adjusting the motor speed to achieve energy saving, in the load rate is low, the motor speed is reduced, the main equipment and corresponding auxiliary equipment such as bearing wear is reduced, maintenance period can be extended, extended operating life of equipment; and after the transformation of the variable frequency air damper opening degree of up to 100%, operation does not bear the pressure, can significantly reduce the throttle maintenance. In the operation of the frequency converter, it is only necessary to dust the converter regularly, without stopping the machine to ensure the continuity of the production. With the need of production, adjust the speed of the fan, and then adjust the air volume of the fan, not only meet the requirements of the production process, but also greatly reduce the intensity of the work. By adopting frequency conversion technology, the mechanical wear and tear are reduced, the maintenance workload is reduced, and the maintenance cost is reduced.
(3) after using the frequency conversion device, the motor can be soft start, the current is not more than 1.2 times the rated current of the motor, no impact on the power grid, the motor service life is prolonged. Throughout the operating range, the motor can be guaranteed to run smoothly, the loss is reduced, the temperature rise is normal. The noise and starting current of the fan is very small, and there is no abnormal vibration and noise.
(4) compared with the original old system, the inverter has over current, short circuit, over voltage, under voltage, lack of phase, Wen Sheng and so on a number of protection functions, more perfect protection of the motor.
(5) the operation is simple, the operation is convenient. The intelligent regulation can be realized by the computer remote given parameters such as air volume or pressure.
(6) to adapt to the power grid voltage fluctuation ability, wide voltage working range, the power grid voltage fluctuation between +10% ~ -15%, the system can be normal operation.

四、Concluding remarks
In summary, in order to save energy and cost, frequency conversion and energy saving reconstruction of the fan system, so as to achieve the purpose of saving energy and prolonging the service life of the motor, contactor and mechanical parts, bearings, valves, pipe. Generally speaking, for the continuous work of the air supply system, with the change of the process, the motor operating frequency of 35 ~ 50.00Hz between the dynamic adjustment, the system power saving rate of up to 20% ~ 35%.