Motor control center, also known as motor control center or motor control center, the English name for MOTOR CONTROL CENTER, referred to as MCC. The motor control center manages the power distribution and instrumentation equipment in a unified manner and houses a variety of motor control units, feeder connector units, distribution transformers, lighting panels, interlock relays and metering equipment into an integrally installed enclosure and by a common Closed bus power supply.
Motor control center, also known as motor control center or motor control center, the English name for MOTOR CONTROL CENTER, referred to as MCC. The motor control center manages the power distribution and instrumentation equipment in a unified manner and houses a variety of motor control units, feeder connector units, distribution transformers, lighting panels, interlock relays and metering equipment into an integrally installed enclosure and a common Closed bus power supply.
In all fields of national economy, such as electric power, petroleum, chemical industry, metallurgy, mining, paper making, light industry, automobile, shipbuilding industry, transportation, municipal construction, food and beverage, water treatment, garbage disposal, The more widely used. In order for the motor to operate normally and reliably, a single motor and a production line motor need to be uniformly controlled and protected .
Therefore, the level of motor control center MCC has also been rapidly developed. MCC refers to the AC low voltage circuit will be connected to a full set of motor control and protection equipment, according to a certain standard system assembly into a standardized unit components Each component control of a motor of the corresponding specifications, the standard unit assembly into a cabinet to achieve multiple Centralized control of the motor.
The development of MCC
MCC (Motor Control Center) is widely used in engineering. Conventional MCCs include only electromechanical components, and all connections are made through hardwiring. Until today, these electromechanical components are still a major part of MCC products. Even in developed countries, more than half of the MCC products are still mechatronic devices. In recent years, with the development of science and technology, intelligent MCC development and gradually applied. Intelligent MCC uses new intelligent components and field bus technology, and gradually integrated automation development, the hardware, software and networking technologies closely linked together.
Traditional Motor Control Center (CMCC)
The traditional motor control center (CMCC) can realize the start-stop control and simple fault detection of the motor with reliable performance and maintenance. It is widely used in all fields of national economy, especially in petrochemical, metallurgy, papermaking, building materials, textile and food Processing, pharmaceuticals, electricity and other processes that require process control.
Intelligent Motor Control Center (IMCC)
The Intelligent Motor Control Center (IMCC) is powerful and provides motor position and speed servo control, a wide range of motor fault detection and diagnostic functions, and is used in a wide range of complex process control applications.
CMCC and IMCC can be used alone to complete the motor control, but also can be used as distributed control system DCS or programmable logic controller PLC on-site actuators, together with the control tasks, is the key plant automation equipment.
Traditional MCC working principle and existing problems
Conventional MCCs are hard-wired, with remote connections of control cables and signal cables to the DCS system housing the MCC room. DCS control commands and feedback information of the MCCs are transmitted over the cable. Each of the multiple cables (as shown in Figure l Shown). The traditional MCC control has the following problems:
① a huge number of control and signal cables;
② site needs remote I, o cabinet;
⑨ wiring workload, installation, commissioning cycle length;
④ more wiring, so the point of failure, the cause of the accident is not easy to find;
⑤ in the increase of equipment loop, to be re-laying control and signal cables, not easy to expand:
⑥ management for production and operation, less diagnostic information, poor operation and maintenance of electrical equipment;
⑦ spare parts quantity, not easy to unify, occupy large funds.
Working Principle and Features of Intelligent MCC System
Intelligent MCC system is a new type of electrical automation control system combining information technology, sensing technology and computer data processing technology. Its core components are intelligent motor protectors with communication functions, control commands of DCS and relevant operation information of the electric motor are transmitted through the bus Communication way, the field bus such as Lonwbrks, PROFIBUS, Etllemet, TCP, may dispose the spare communication interface according to the need. Its characteristics are as follows:
① DcS site without the cabinet, usually each communication bus can control up to 100 motor circuits
② less line contacts, anti-interference ability, the cause of the malfunction clear, easy to find exclusion;
③ using bus communication, installation, commissioning cycle is short;
④ increase equipment loop, as the system allows, just set in the software, easy to expand, flexible;
⑤ rich operational management information can provide detailed equipment maintenance information, preventive maintenance equipment can be done to minimize unexpected equipment downtime:
⑥ with spare parts management capabilities, fewer spare parts, can reduce the capital occupation.
Comparative Analysis of Intelligent MCC and Traditional MCC
1) From the hardware point of view, smart MCC connection is quick and easy.
Traditional MCC and basic automation There are two main ways to connect, first, by setting up a remote I / 0 cabinet in the MCC cabinet, MCC monitoring control signal is connected with the control cable, and then by the remote I / 0 station via the field bus Communicate with PLC The other is the MCC monitoring control signal directly through the control cable connected to the PLC's local I / O cabinet. The point-to-point control signal connection determines the number of cables, construction volume.
The smart MCC offers outstanding performance in this area. After connecting to the field devices, only one DEVICENET fieldbus is needed to enable the MCC to communicate with the underlying automation. This eliminates the need for control cables and I / O cabinets These intermediate links make the connection easier and faster.
2) Due to the introduction of the DEVICENET fieldbus, the control cables and the large number of I / Os are eliminated, the number of PLC rack shelves is also reduced, and the cost of the control system integration is reduced. Offset the smart MCC slightly higher than the traditional cost of MCC disadvantage.
3) System debugging, the system RBI, greatly reducing the commissioning time; and does not require PLC I / O terminal cabinet and the middle relay cabinet, the system greatly reduce the point of failure.
4) From the maintenance point of view, the reduction of intermediate links makes maintenance easier. Single from the PLC status monitoring information to determine the status of field equipment and fault conditions.
5) Intelligent MCC control system is open and scalable, which is unmatched by traditional MCC. Application of Fieldbus and Configuration Software Technology in Sewage Treatment Project.