Introduction：
Paper industry is an important basic raw material industry closely related to the development of national economy and social undertakings, and an important pillar industry of my country's national economy. At present, more than 80% of the transmission equipment of new paper machines have adopted AC drive inverters.
Refiner is a very critical part of pulp production. Its pulp production line is composed of a series of supporting equipment. In order to improve production efficiency and ensure the quality of pulp, each transmission part needs a high degree of coordination. At present, the important transmission of advanced production lines adopts frequency conversion. drive. D71 inverter has a wide range of applications in the paper industry.
Features：
D71 is a wall-mounted inverter, the power range is 0.75KW-500KW, the voltage level of the incoming line voltage is 380V-480V, and the control method is vector control without speed sensor.
D71 has a wealth of control devices, including 8 digital inputs (LI1-LI8), 2 analog inputs (AI), 2 relay outputs (TA), 2 analog outputs (AO), 5V auxiliary power supply for analog power supply Fixed input, 24V auxiliary power supply is used for digital input, all LI/TA, AI/AO can be freely programmed to define functions.
MODBUS interface is standard configuration of D71, no option is required. The D71 can be connected to higher-level automation systems via MODBUS.
Advantage：
Large starting torque, 1.5 times the torque output at open-loop 0.5Hz, meeting the requirements of refiner operation;
It has the advantage of fast torque response, and when the load fluctuates, the current fluctuation is small;
It has good overload capacity and environmental adaptability, and has high operational reliability;
Super power grid adaptability, anti-power grid fluctuation ability up to ±15%, to ensure the stability of output voltage, current, speed
Excellent current limiting characteristics, strong overload capacity, can effectively reduce frequency conversion overload, overcurrent protection, and maximize production continuity;
It has strong environmental adaptability, and the completely independent air duct design can greatly improve the resistance to harsh environments such as oil pollution, dust and damp heat.
System Introduction：
In this system, the 110KW main motor of the refiner is driven by the D71 110KW inverter, and the central control system DCS is connected with all the executive components and sensors of the entire production line to monitor the field conditions of each transmission system in real time. The central control system controls the start-stop, frequency setting, fault reset and other commands of all inverters, and simultaneously collects data such as current, voltage, bus voltage, and operating frequency of all inverters to monitor each inverter in real time.
Technical Parameter：
| Inverter technical parameters | Device configuration | |
 Model: D71-X | Output current: 215A | One D71 inverter |
| Input voltage: 3-phase, 380-480V | Frequency range: 0-400Hz | 110KW refiner main motor |
| Input frequency: 50/60Hz ±5% | Overload capacity: 150%, 60 seconds | Central Control System DCS |
| Output power: 110KW | Ambient temperature: -10-40°C | Sensor |
| Output voltage: 0-480V (the maximum value is determined by the input voltage) | Protection level: IP20 | |
On Site Usage：
According to the on-site space situation, a D71 series inverter is installed in the control cabinet, and the inverter installation and on-site motor are as shown in the figure
Running Result：
The refiner control system using D71 inverter has been put into operation for more than three years, and has achieved good economic and social benefits:
The control device operates reliably, has good environmental adaptability, can resist harsh environments such as oil pollution, dust and damp heat, and has a low failure rate;
Excellent current limiting characteristics, strong overload capacity, can effectively reduce frequency conversion overload, overcurrent protection, and maximize production continuity;
The feeding amount is controlled by the actual running current of the motor, and it has overload pre-alarm function and trip-free function, which can ensure the safety of the motor and the continuity of production;
The economic benefits are remarkable, the power saving effect is more than 20%, and the entire investment increased by the frequency conversion control system can be recovered in more than one year.
Customer Benefits：
Convenient speed regulation, which can ensure the most uniform mixing of paint and medium;
Reduce the loss of gearbox, greatly save maintenance costs;
The comprehensive protection function of the frequency converter ensures maximum production continuity;
Online stepless speed regulation, different varieties use different grinding speeds;
The economic benefits are significant, and the entire investment increased by the frequency conversion control system can be recovered in more than one year