Used frequency converter:
MIDIMASTER Vector
Model MDV 750/3
Input voltage 3 phase, 380-500V ± 10%
Input frequency 47-63 Hz
Output power 11kW
Output voltage 0-500V (maximum depends on input voltage)
Output current 19A (23.5A at variable torque load)
Frequency range 0-650 Hz
Overload capacity 150%, 60 seconds Ambient temperature 0 ± 40°C
Protection class IP21 (or IP56)
Equipment configuration:
* One MDV 750/3 encoderless vector control inverter
* One RGZZESD three-phase squirrel-cage motor,
10HP, 1470RPM
* DCS distribution system and field monitoring instruments
Users benefit:
* Small amount of reliable maintenance, saving maintenance costs and increasing enterprise economic benefits;
* As a general-purpose inverter, MDV has an optimized multi-channel analog/digital I/O. The on-site operation loop and DCS control system can use them conveniently and flexibly to complete the control of the production process and realize the speed control and operation monitoring of the inverter.
Control features:
* The mixer load has a viscous effect during starting. The continuous lifting function (parameter P078) and the starting lifting function (parameter P079) of the inverter can provide 250% of the motor rated current during low frequency operation and acceleration of the mixer, increasing the low frequency of the motor. Torque and starting torque meet the requirements of mixer operation.
instructions:
The mixer's speed control accuracy, dynamic and static quality requirements of the drive are not high, as long as it can operate in accordance with the DCS speed command stable and reliable, it can meet the production requirements.
The operating circuit is shown in Figure 2. This is an open-loop control system. The start/stop operation signal of the inverter comes from the field operation column or DCS system. The analog speed reference is provided by the DCS (terminals 3-4 in Figure 2). At the same time, the drive feeds back to DCS the actual speed value of a motor (terminal 12-13). Based on the meter measuring signal and the actual speed value of the stirring tank, the operator sends an instruction to increase or decrease the motor speed reference value to the frequency converter.
Overview:
The catalyst mixing process of a polypropylene plant in Yanhua is shown in Figure 1. The catalyst is fed from the tank to the mixing tank through the ball valve. Inverter-driven motor drives stirring blade to stir, and then evenly through the vacuum valve to achieve the required catalyst to the catalyst feed pump to participate in the next chemical reaction.
Control tasks:
The operator in the control room determines the command to increase or decrease the motor speed based on the measured signal from the field monitoring instrument and the actual speed signal sent from the inverter to the DCS system, and starts and stops the agitation when necessary.
Control features:
Unlike some frequency converters, the MDV must remain disabled after the inverter is powered on and either press the "RUN" button on the keypad or connect an "ON" via terminal 5 or 6. After the signal is released, the inverter output is released. Otherwise, if terminal 5 or 6 is directly connected to ±15V, the inverter may be damaged when the inverter is powered on. In the figure, the normally open contact (terminal 21-22) of RL2 is closed after the power-on self-check is normal, and terminal 5 is connected to the “ON†signal to allow the output of the inverter to be released, ensuring the safety of the inverter.
running result:
The designer of the control circuit through the full understanding of the function of the frequency converter, make full use of the hardware resources of the device itself, designed a reasonable and correct control loop to meet the production requirements.
MDV has continuous lifting and starting lifting functions. It has viscous action at start-up, and the mixer load that requires additional torque during low-frequency operation and acceleration can provide a total of 250% of the motor rated current, enabling smooth mixing.