Ⅰ.·Renle high voltage frequency conversion internal mixer application

1. When the motor is started at power frequency, the instantaneous current is as high as 6 to 10 times the rated current, which is likely to affect the power grid. At the same time, the frequent power frequency starting of the motor is likely to damage the motor. The starting current of the inverter is generally less than the rated current of the motor, and it can also limit the current within 200% when starting with an overload.

2. The operation cycle of the internal mixer is generally 3~6min, and the high overload operation time is generally about 2%, that is, 3.6s-7.2s, which is divided into two to three times. Each torque response is required to be performed within milliseconds Power frequency control has a big impact, and variable frequency vector control can effectively solve this problem.

3. When the inverter is controlled, the high power factor can save energy and avoid energy waste.

4. The frequency converter can be stepless speed regulation. The frequency converter controls the asynchronous motor and can completely replace the two-speed motor and the DC motor. It can solve the problem of inconvenient maintenance of the DC motor, and does not require a transformer, and a reactive power compensation harmonic control device. There are great advantages in cost and maintenance.

The cost analysis of the internal mixer drive system is shown in the following table:

Table 1. Investment comparison:

system Compare project	A. DC motor + DC drive		B. AC low-voltage motor + AC low-voltage inverter (690V class)		C. AC high voltage motor + AC high voltage inverter
	Description	Price(ten thousand yuan)	Description	Price(ten thousand yuan)	Description	Price(ten thousand yuan)
a. Inlet transformer	One 2500KVA transformer	20	One 2500KVA transformer	20	no	0
b. Wire and cable	One set of DC drive cabinet input 660V rated current 2000A overload 200% 1 minute	21	A set of 690V low voltage frequency conversion (closed loop) rated power 1500KW overload 200% for 1 minute	120	6000V/10KV high-voltage inverter, a set of 1500KW overload capacity 200% for 1 minute	100
c. Wire and cable	3*240mm2 cable 900m	21	3*240mm2 cable 900m	21	3*70mm2 high voltage cable 300m	7
d. Motor	A DC motor 750V1500KW	45	A squirrel-cage AC motor 690V1700KW	45	A high-voltage squirrel-cage AC motor 6000V/10KV1500KW	45
e. Harmonic suppression device	Need to be equipped with harmonic suppression devices according to grid requirements	20	Need to be equipped with harmonic suppression devices according to grid requirements	20	no	0
f. Other	Transformer room	20	Transformer room	20	no	0

One-time total investment amount

A. DC motor + DC drive

a+b+c+d+e+f=1.61 million

B. AC low-voltage motor + AC low-voltage inverter (690V class)

a+b+c+d+e+f=2.42 million

C. AC high voltage motor + AC high voltage inverter

a+b+c+d+e+f=1.52 million

Table 2: Comparison of maintenance and use

System Equipment	A. DC motor + DC drive	B. AC low voltage motor + low voltage inverter	C. AC high voltage motor + high voltage inverter
Motor	There are electric brushes, requiring regular maintenance; high requirements for air humidity; high frequency of failures; high technical requirements for maintenance personnel	Large harmonic components, low power factor, high heat generation of the motor, easy aging of the stator coil	Small harmonic components, high power factor, long motor life, no routine maintenance
driver	When damaged, it must be shut down for maintenance	When damaged, it must be shut down for maintenance	When the power unit is damaged, no shutdown, no derating, guarantee the discharge
transformer	Regular maintenance and testing are required, generally 0.5~1 year/time	Regular maintenance and testing are required, generally 0.5~1 year/time	no
cable	High heat is easy to aging, and the update time is short; the cable connector has large contact current and is easy to be broken	High heating is easy to aging, and the update time is short; the cable connector has large contact current and is easy to aging	The current is small, the heat is small, and the service life is long; the cable connector has small contact current and is not easy to damage

It can be seen from the above table that the use of high-voltage variable frequency drive motors has obvious advantages in terms of one-time investment and maintenance costs.

Ⅱ, the advantages of Renle high-voltage frequency conversion speed control device internal mixer industry application

1. The special high-voltage frequency conversion speed control device for Renle's internal mixer is a high-voltage frequency conversion speed control device specially developed and designed by Renle for heavy load systems such as internal mixers in the rubber industry. This product integrates international power electronic technology and vector control technology. Not only does it have the same excellent control performance as the international high-end frequency conversion speed control device, but also combines the characteristics of China's use environment, especially for the application of heavy load systems such as internal mixers. Many special measures have been taken to make the product reliable Performance, environmental adaptability and customer personalization can fully meet the various needs of internal mixers in the rubber industry and other similar heavy-duty applications.

2. The special high-voltage frequency conversion speed control device for Renle series internal mixer adopts the unit module series multi-level technology, which belongs to the voltage source type inverter. The power unit adopts the AC-DC-AC method, which is highly reliable and easy to operate.

The grid voltage is isolated and phase-shifted by the transformer to supply power to the power units. Each power unit is a single-phase AC-DC-AC voltage inverter. The units are connected in series to form a three-phase variable frequency power supply to power the high-voltage motor. According to the number of series units, the products are divided into 6kV and 10kV series. The main transformer adopts a phase-shifting rectification method with high input power factor, and the input voltage and current harmonics meet the strictest harmonic distortion requirements of IEEE519-1992 and GB/T 14549-93 for voltage and current. No need for any power factor compensation and harmonic suppression devices. The inverter output adopts multiple PWM technology, the output is almost perfect sine wave, no need to add output filter. The motor harmonic loss is small, the torque ripple is small, and there is no obvious motor noise. The motor does not need to be derated for use. The output dv/dt and common mode voltage are small, and there is no additional electrical stress damage to the motor.

3. Technical characteristics of Renle’s high voltage frequency conversion speed control device

1) The frequency conversion device adopts the latest design and manufacturing technology, and the internal components adopt high-quality imported components, which have a long service life and the most simplified system design, which improves the reliability of equipment operation and ensures the quality of the entire inverter;

2) The high-performance controller integrates DSP, FPGA, CPLD, and PLC devices with clear division of labor, safety and reliability.

3) The built-in PID regulator and fuzzy control regulator are integrated and designed for closed-loop control, and an external regulator can also be used for closed-loop control.

4) The remote communication monitoring interface of the controller system is RS232/RS485, which can flexibly support communication protocols such as Modbus and Profibus.

5) When the undervoltage of the high-voltage main power supply reaches 65%, it will not stop, and the inverter will automatically derate to run. After the voltage returns to normal, it will automatically return to the original set speed.

6) Using precise control technology, superimpose controllable high-frequency components on the output voltage vector through vector algorithm, so that the motor produces greater resistance torque, accelerates the braking of the motor, and greatly reduces the speed reduction time.

7) The power grid can be restarted automatically after a momentary power failure.

8) Complete power unit protection and system protection, accurate fault diagnosis and positioning, and complete historical fault records and operation records.

9) The PCB board automatic welding production line has greatly ensured the quality of the PCB board, and truly grasped the quality firmly in their own hands.

The above technical characteristics have greatly improved the performance and reliability of the product, and some of the performance has been similar to the products of internationally renowned manufacturers.

4. Special personalized design for internal mixer

○ Vector open loop/closed loop control mode

○ Meet the overload requirements of internal mixer

○ Meet periodic load requirements

○ Meet the requirements of variable speed rubber mixing in internal mixer

○ Meet system speed stability requirements

○ Meet the process requirements of internal mixer, user-specific second controller (temperature mode, time mode, power mode, viscosity balance mode to establish a digital model)

5. The special high-voltage frequency conversion speed regulating device for Renle internal mixer has unique technical advantages on internal mixer:

1) The vector control method is adopted, with high control accuracy and fast response speed, which effectively improves the level of production automation, improves the production process, and meets the requirements of safe operation of internal mixer loads;

2) The hardware configuration is high, the overload capacity is strong, and the 2 times overload can last for one minute, which can meet the periodic overload needs of the internal mixer;

3) Operation method, providing a sufficiently high starting torque, according to different production processes, by directly adjusting the motor speed to achieve energy saving, reduce the wear of the main equipment and corresponding auxiliary equipment, make the equipment maintenance cycle longer, and extend the equipment operating life;

4) Almost no high-order harmonics, no pollution to the power grid, no damage to the motor, no need to configure a grid filter device, improve the power factor to 0.96, and reduce reactive power loss;

5) With the motor soft start function, reduce the motor starting current, reduce the motor start impact, and reduce the operating noise;

6) The use of carrier wave technology makes the shaft system of the internal mixer hardly feel the pulsating torque, reduces the vibration of the internal mixer equipment, reduces the heating of the equipment, and extends the life of the equipment;

7) Abundant and changeable mechanical characteristic curves, which can realize stepless speed regulation, meet the technological requirements of different machines and rubber materials, and meet the requirements of variable speed rubber mixing process;

8) Integrate a variety of on-site control methods, flexibly configure corresponding control methods according to different site needs, and have large software storage space and strong scalability;

9) System integration design, easy to use, users only need to provide cable wiring;

10) The trigger adopts the form of optical fiber, and the high and low voltage in the cabinet are completely isolated, with good safety and strong anti-interference ability;

6. Bring benefits to users:

1) Energy saving effect: The energy saving effect of the internal mixer measured on site is about 18%.

2) Extend the service life of the equipment: reduce the impact on the power grid and the motor when the internal mixer starts, the main equipment and the corresponding auxiliary equipment (such as mechanical transmission parts, bearings, etc.) are less worn than before, the maintenance cycle is longer, and the equipment operating life is extended.

3) Improve product quality: The level of production automation is improved, and the production process is improved. In the process, the high-precision speed adjustment of the compacting machine can be guaranteed, and the speed will not be lost in the case of sudden load changes, making the process control more stable and the quality of the produced products guaranteed.

4) Reduce on-site noise: The noise is greatly reduced, the working environment conditions are improved, and the on-site operators have responded well.

5) Improve power factor: When the original motor is directly driven by industrial frequency, reactive power compensation is used, and its actual operating power factor is 0.92. After adopting the high-voltage variable frequency regulation system, the power factor on the power supply side can be increased to above 0.96, and the reactive power can be greatly reduced without the need for reactive power compensation devices, meeting the requirements of the power grid, and further saving the operating costs of upstream equipment.