Variable Frequency Speed Bridge Crane
Practical Application of Variable Frequency Speed Regulation Technology in Bridge Crane
Bridge Crane in industrial and mining enterprises have a wide range of applications, mainly used to achieve the object movements and transport. Alumina industry distribution department packaging workshop bridge crane, a device every day into and out of aluminum oxide powder amounted to more than 2,000 tons, the use of frequent, heavy workload, and the environment is bad (with alkaline corrosion dust). Bridge crane can directly affect the normal work of the packaging workshop production efficiency and the completion of the task, and even related to the personal, equipment safety.
2 issues raised
The Department of the packaging plant used the original bridge crane drag system with winding AC induction motor, the rotor loop into the multi-level external resistor to grading speed, the use of cam controller, relay contactor control, which Speed regulation is simple, but there are many shortcomings:
(1) winding rotor resistance of the mechanical characteristics of the speed control soft, slow speed performance;
(2) series resistor speed control is a step-speed mode, through the contactor to complete the division of the rotor series resistance switch, which adjusts the motor speed, resistance switching will be on the power grid and the crane mechanical parts Unavoidable impact;
(3) The main circuit in the use of positive and negative contactor to achieve the motor commutation, the actual operation of the bridge crane operator in order to adjust the working condition, the frequent use of reverse braking (commonly known as playing anti-car), switching current, And the motor working condition is bad, equipment maintenance cost is very high;
(4) Crane start, the speed of the rotor when the string resistance is pure energy-consuming components, waste a lot of power. In addition, due to the speed resistance of the restrictions, narrow speed range, starting torque is small, extended start time, affecting production efficiency;
(5) the system brake is carried out in the state of motion, the brake is damaged, brake wear serious.
In view of the actual production problems, decided to implement the packaging crane bridge crane by the new linkage, PLC and high-performance frequency control devices consisting of the overall technological transformation solutions.
3 system transformation program implementation
3.1 System Configuration
Packaging workshop bridge crane electric drive system with cart motor 7.5kW × 2 units, car motor 2.2kW × 1 units, winch motor 15kW × 1 units. Implementation of the technological transformation program uses three sets of frequency converter control of four motors, including hoist motor and car motor with an ACS800-01-0040-3 and ACS800-01-0005-3 inverter drive, cart two motors Then use an ACS800-01-0030-3 inverter drive, to achieve synchronous operation, each inverter configuration of the energy consumption of braking components, the location of potential energy and braking energy consumption. System configuration Siemens S7-200 small programmable logic controller constitutes the center of the entire control system, configure the new linkage control console to replace the original cam controller, to achieve system operation.
3.2 The main features of the control system
(1) the original four AC induction motor rotor center point directly shorted, all the rotor circuit of the cable, resistors, frequency sensitive rheostat and contactor all canceled.
(2) in the traffic upload 3 stainless steel control cabinet, protection class IP54. The winch frequency conversion control cabinet is one, the big, the car frequency conversion + PLC control cabinet one, the brake resistance cabinet one, the stainless steel cabinet has realized the anticorrosion, the moistureproof, the dustproof goal, adapts the alumina profession to have the corrosive dust harsh working environment request.
(3) The frequency changer chooses ABB ACS800 series high performance frequency changer, the frequency changer system which controls the winch motor uses the hoist application macro, the control big, the small car electrical machinery frequency changer system software selects the standard application macros.
(4) PLC selection SIEMENS S7-200 series, the control handle issued to the PLC to open, stop, fast, slow, upgrade, decentralization and other instructions, the corresponding PLC command to control the inverter forward and reverse speed, in order to achieve Optimal Control of Bridge.
(5) When the inverter generates the braking torque, the motor receives the mechanical energy from the load and turns it into the electrical energy into the inverter, which causes the DC voltage to rise. At this moment, the inverter must deal with this part of energy, otherwise the DC circuit capacitance Over-voltage protection action will stop its operation, so the inverter DC circuit set braking unit and braking resistor, the crane in the descending brake release of energy consumed in the braking resistor.
(6) PLC according to the control procedures, input control signals and upgrade, decentralization and other instructions to complete the various conditions of the crane coordination and control.
(7) linkage console has two, multi-speed control.
Winch linkage console: Winch independent control of a single handle operation, has to improve fast, medium and slow third gear speed, decentralized fast, medium and slow third gear speed, and parking and other items.
Large and small car linkage console: large car sharing a handle operation for the full range of operating handle, you can control large and small cars, also have fast, medium and slow and stop control functions.
3.3 system fault protection and fault diagnosis of the main features
The inverter has perfect protection functions for the motor and the inverter itself, such as overheating, overload, overcurrent, overvoltage, phase loss, grounding, etc., so as to avoid equipment from abnormal operation for a long time and protect equipment from damage.
In addition to fault information can accurately indicate the point of failure, but also shows the cause of the failure and troubleshooting measures, which greatly facilitates the maintenance staff troubleshooting.
Operation in the event of failure to stop operation is also very simple to reset operation, as long as the failure to press the fault reset can be.
4 after the transformation of the control system to achieve the actual results
(1) the use of frequency control after the transformation to achieve a smooth speed, and the efficiency is extremely high, and the original series resistor speed mode, start more stable, more accurate positioning;
(2) The system is controlled by the control handle to the output of the inverter, adjust the motor speed, easy operation, speed range, can be set to run speed;
(3) ABB inverter and dedicated hoist application macro are used in the system to realize the full torque output (up to 300% of rated torque) of the inverter at zero speed and the internal integrated brake logic control, Improve the stability and reliability of system application;
(4) winch, the size of the car starting, braking, acceleration, deceleration and other processes more stable and fast, more accurate positioning, energy-saving effect is obvious, according to test energy-saving rate of up to 35%;
(5) the control loop is simple, to achieve a soft start, soft stop, no impact on the gear, the motor, low failure rate, easy to maintain, greatly reducing maintenance costs;
(6) As the system has further functional expansion of the interface, according to the actual needs of the future expansion of wireless remote control, field bus communication and other functions;
(7) from the transformation put into operation 1 # packaging plant 2 bridge crane situation, a good solution to the motor starting and stopping the impact of current, coupled with the motor to improve the protection of the motor, Greatly improving the reliability of the traffic and safety, extended service life.
Since the system has been put into operation, it has achieved the expected purpose of reforming, and its operation is good. It has excellent speed performance, stable starting, accurate positioning, safe and reliable operation, simple operation, remarkable energy saving and small size. It has wide application in the same industry. value.