Frequency conversion and energy saving of the hott

Frequency conversion energy saving of injection molding machine

why can frequency conversion technology make injection molding machine energy saving

1. "Big horse pulls small car" phenomenon

the hydraulic system of the injection molding machine is a load with large fluctuations in pressure and flow. In different working stages such as mold closing, mold locking, glue injection, pressure maintaining cooling, mold opening and ejection, its pressure and flow will change regularly. The typical pressure and flow curve is shown in the following figure:

it can be seen from the above figure that in a working cycle, The actual pressure and flow of the injection molding machine vary, sometimes large and sometimes small, sometimes almost zero. When the actual flow is small, the oil supply of the oil pump is far greater than the actual consumption of the load, and the supply exceeds the demand. All the surplus hydraulic oil under high pressure overflows through the overflow valve. Under high pressure, the hydraulic oil releases a large amount of heat energy after overflow. This part of the dissipated energy is actually part of the electric energy absorbed by the oil pump motor from electricity. Due to the long maintenance time of small flow, the dissipated electric energy is also larger. Therefore, there is a serious waste of energy in the hydraulic system of injection molding machine, that is, the waste of "big horse pulling small car" is serious

2. Frequency conversion energy saving

from hydrodynamics, P (power) =q (flow) × H (pressure), flow Q is directly proportional to the power of speed n, pressure h is directly proportional to the square of speed n, and power P is directly proportional to the cube of speed n. It can be seen from the above formula that if the efficiency of the oil pump is certain, when it is required to adjust the flow Q to decrease, the speed n can decrease proportionally, and at this time, the output power P of the oil pump decreases in a cubic relationship. For example, if the rated power of an oil pump motor is 55kW, when the speed drops to 4/5 of the original speed, its power consumption is 28.16kw, saving 48.8%; When the speed drops to 1/2 of the original speed, its power consumption is only 6.875kw, saving 87.5%

① the pipeline condition remains unchanged, and the ideal relationship between the required power and flow (speed)

② when adjusting the outlet valve (baffle), the relationship between the required power and flow

③ when adjusting the inlet valve (baffle), the relationship between the required power and flow

④ the pipeline condition remains unchanged, and the relationship between the power and flow required for regulating slip speed regulation

⑤ the pipeline condition remains unchanged, and when variable frequency speed regulation, The relationship between required power and flow

above is the ideal energy-saving situation of non closed fluid system. Such an ideal energy-saving effect cannot be obtained for closed fluid system, but each physical quantity has a similar relationship

it's the coherence of each other studied by experts. 3 Using frequency conversion technology to control the energy saving of injection molding machine can also obtain the following benefits:

achieve the purpose of improving efficiency and indirect energy saving

reduce the oil temperature and improve the service life of hydraulic parts

improve the consistency of product quality (weight)

when adding injection molding machine, there is no need to expand the capacity of electricity

the core problem of energy-saving transformation of injection molding machine

1 The problem of power saving rate

2 Efficiency problem

reactive power not only increases line loss and equipment heating, but also reduces active power due to the reduction of power factor. Ordinary quantitative pump injection molding machine cos Φ Value is 0 8. After using the energy-saving cabinet with variable frequency speed regulation, cos is reduced due to the function of the filter capacitor in the frequency converter Φ Thus, the reactive power loss is reduced and the active power of electricity is increased

because the response time of the motor controlled by the frequency converter is greater than the action time of the valve at power frequency, therefore:

when the set parameters of the original injection molding machine are not changed - the processing efficiency is 95% - 98%

when the set parameters of the original injection molding machine are allowed to be changed - the processing efficiency is 99% - 101%

3 Noise problem

adopt internationally advanced dead time compensation technology to greatly reduce high-order harmonic current, make the current waveform closer to sine wave, and reduce motor noise

4. The problem of anti-interference

pulse width modulation (PWM) technology adopts soft switching technology, which greatly reduces external interference

5. The price of motor lithium carbonate gradually falls down, and the service life problem

because the motor is started directly or y/d, the starting current is equal to () times the rated current, which will cause serious impact on electromechanical equipment and power supply, and will also have too high requirements for capacitance. The large current and vibration generated during startup are extremely detrimental to the service life of the equipment. After using the frequency conversion energy-saving cabinet, the soft start function of the frequency converter will make the starting current start from zero, and the maximum value will not exceed the rated current, which reduces the impact on electricity and the demand for power supply capacity until it reaches the high point and swings back to the low point, and prolongs the service life of the equipment and mold