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One--Brief introduction

With the development of Various industry, toughened glass has become widely used nowadays, which has been a indispensable material in life. What’s more, the tempered furnace is also a important equipment for glass processing. Glass tempering furnace is a equipment through glass-heating and after that quenching technique, making the surface of glass form the pressure stress after cooling, after that the inside glass form the tensile press, thus improving the intensity of the glass, making the ordinary annealed glass become toughened glass.

   With the mature of frequency conversion technology and the wide application of frequency converter(inverter).In the current situation of increasingly tight energy, the way to the motor variable frequency speed control technique use for air volume control of the fan and the regulating motor speed to adjust the air volume has replaced the traditional fan which with constant speed running and the way depends on the Shutter Valve to adjust air volume. The energy saving effect is remarkable.

                    Picture 1 Glass toughened furnace production line

Two---Glass tempered furnace equipment and tempered process

Glass tempering furnace is equipment which the common glass is under heating to a softening temperature and use powerful airflow to spat cooling, makes Glass quenched a Toughened glass. The picture below,

 

Picture 2, Composition of glass toughened furnace

2.1. First put the ordinary glass to Reciprocating heating room until it is evenly heated to the glass softening point, After the glass softening, it will proceed to a extreme quenching to finish toughened glass.

2.2.A centrifugal fan is used for quenching.
2.3.According to the thickness of the glass, the centrifugal fan speed is blowing quench cooling to the back and front side of the glass according to the parameter set by the the upper computer of the control system and powerful airflow is generated with different flow size.

2.4.After glass though tempered quenching, it will forms the pressure on its surface, and when the glass is subjected to external forces, the surface stress is first offset, thus improving the carrying capacity and improving the tensile strength of the glass.

Three---The principle of energy saving and transformation of frequency converter

Variable frequency energy saving reconstruction of the toughened furnace fan application on frequency inverter with the function of air-volume optimizing industrial control on upper computer machine, setting different function code for different kinds of products, so as to realize the demand of different kinds of glass production technology. The frequency inverter under the control of PLC can be change according to the needs, making fan running at the most energy saving state.
3.1 Standby phase of fan

When the glass is in the heating stage, the fan is in standby mode, and the fan outlet is closed. The PLC output about 7.2mA analog signal to the frequency converter, the corresponding output frequency of inverter is 10Hz, the fan is in standby operation. When the fan is in standby state, it will run and maintain at a low frequency so that the fan can timely accelerate to the speed that quenching needs.

3.2. Fan speed up phase 30 seconds before quenching

Before 30 seconds When the glass which is finish heat softening that is going to send to the air blast quenching zone, set PLC output corresponding analog value to inverter according to the frequency of upper computer machine to make the fan accelerate the quenching speed, At this stage the fan speed can accelerate from the standby state to the rated speed of 80% to 100%.after the completion of being heating, the high temperature glass is quickly send to the quenching cooling zone, the wind brake is quickly pulling off, the powerful flow is going into the wind gate though air hose, blowing evenly over the top and bottom of the glass, make the glass extremely quenched to reach the purpose of the steel.

3.3 The quenched stage acquire different air volume according to the thickness of the glass, means the fan speed is different. In addition to the partial thickness of the glass below 4.3mm, usually the fan runs under rated frequency of 85%.The equipment can meet the requirements of most glass quenching process. Due to the fan speed at rated speed 85%, the output shaft power is 61% of the rated power. In the process of the quenching, adopting frequency conversion and using a louver valve to adjust air-volume is more energy saving.

Four---on-site application cases and pictures

4.1 PI500 series frequency inverter features
   

               Picture3 PI500series frequency inverter

The features of PI500series frequency inverter

Adopt DSP as core control unit to realize high speed high performance.

Three speed control methods: V/F, no PG vector control, with PG vector control.

Support the vector control of asynchronous motor and permanent magnet synchronous motor, accurate motor parameter self-learning.

Under the non-inductive vector, the torque output of 0.5hz /150% can be realized. Low speed and high torque, low torque ripple.

Simple PLC function can achieve up to 16 speed control.

Advanced thermal management, independent air duct design, adapt to 40 ℃ environment temperature, fan can be discharge, easy installation and maintenance.

Built-in 485 communication interface, easy-to-use upper computer software, the realization of networked communication with the upper computer, support a variety of communications.

Three anti-lacquer coating treatment, adapt various bad environments.

The instantaneous power cut will not stop.

Global safety certification CE/TUV.

Built-in adaptive PID function module.

With the I/O extension function.

Built-in brake unit.

High protective thin film keypad.

Supports a variety of installation, flange mounting.

Added the QUICK multifunction key and keyboard lock selection

4.2 Site application and Model selection

According to the application and load situation of the site, we have selected the PI500 series inverter for customers, with its excellent acceleration and deceleration characteristics, low frequency high torque, has been wide application in various fields.

4.3.On-site application picture

Picture 4 control cabinet

Picture 5 Images of cooling fan and motor

Picture 6 image of production process

Five, precaution

Please correctly set all motor parameter before operating frequency inverter.

The setting of acceleration time and deceleration time is key. If the acceleration time is too short, the acceleration current will be very big. While if the acceleration time is too long, it will cause unfinished accelerating time when the glass reaches the last quenching zone, which will influence the effect of glass toughened. The slow down time should not be too short.

Six---Conclusion

After the modification of frequency conversion to the fan, the electricity consumption of the fan is greatly decline, the energy saving effect is very significant. At the same time, the fan speed drops, reduces mechanical wear, decrease the failure

rate of the fan and improve the life of the fan. Save cost.