System Overview
Product Name: Fully Digital AC Low-Voltage Variable Frequency Speed Control Electrical System, consisting of a power cabinet (incoming line cabinet), frequency converter cabinet, braking cabinet, network intelligent operating console, humanmachineinterface (HMI), encoder, and other components.
Key Features of the System
1. Main Circuit Control Method:Fully digital variable frequency speed control with sufficient capacity margin.
2. Control Circuit Method:PLC(Programmable Logic Controller) based system.The new-type electrical control system uses fully digital variable frequency speed regulation with Siemens PLC control. The control principles meet hoisting process requirements and incorporate comprehensive hardware and softwareprotection, with key protections implemented in a dual-redundant manner. According to signal flow, the system allows manual or semi-automatic acceleration, automatic deceleration, and automatic stopping.
3. Key Features of Main Control Equipment:
Dual Power Supply Loops: Equipped with corresponding control, measurement, and protection functions; operates in an active-standby mode.
Uninterruptible Power Supply (UPS): Installed in the cabinet to supply power to control devices and PLC, ensuring reliable safety braking and data retention in the event of low-voltage power failure.
Digital Variable Frequency Drive (VFD): Achieves stepless speed regulation for stable operation. Eliminates large rotor resistances, significantly reduces energy consumption, lowers operating costs, and saves floor space.
High Anti-Interference Capability: Strong environmental adaptability, low harmonic content, and grid-friendly. Uses vector control VFD technology forprecise speed tracking. Smooth transition between constant speed, deceleration, and creeping phases, providing superior speed regulation compared to DC-driven hoists.
Advanced Fault Diagnosis: Powerful internal software and external circuit fault diagnostics. Upon detecting a fault, the system automatically stops operation to prevent escalation and provides accurate fault alarms.
System Protection Features
1. Interlock at zero position of main command handle 2. Interlock at zero position of brake control handle 3. Main circuit power-off protection 4. High brake oil pressure protection 5. Reverse direction protection 6. Overspeed protection in constant speed section 7. Overspeed protection indeceleration section 8.Overwind protection 9. Spring fatigue and brake shoe wear protection 10. Deep indicator shaft break protection 11. Ropeslack protection 12. Free-fall (runaway) protection 13. Frequency converter (VFD) fault protection 14. Rope adjustment interlock 15. Constant speed protection 16. Speed limit protection 17. Overload protection (over-capacity protection) 18. Full-load protection 19. Oil temperature protection 20. Hydraulic station residual pressure overlimit protection 21. Rope clutch failure protection 22. Undervoltage protection.
PLC Main Control Station
1. Intelligent CNC Operating Console The console is designed with an intelligent CNC control platform. A central HMI touch screen displays system operating status and working parameters, while also recording parameter variations during operation. It provides audio-visual fault alarms. On both sides, optional cornerconsoles can be configured: Left corner cabinet: equipped with a 22-inch monitor for real-time surveillance of the hoist room and multiple slope- change points.Right corner cabinet: equipped with a 22-inch industrial computer (upper-level computer) for software monitoring, providing dual hardware and software protection for the console.
2. Imported Dual Protection Control The system uses imported Siemens dual PLCs and imported Omron dual encoders from Japan, forming an independent dual-line protection structure.
3. Manual Command Controller & Emergency Brake Equipped with a manual command controller to adjust braking force and hoisting speed. Includes a foot-operated emergency brake switch that ensures reliable dynamic braking energy during normal operation and enables rapid braking in emergencies to prevent accidents.
4. Multi-Mode OperationThe system provides manual, maintenance, and (semi-)automatic start modes. A mode selection switch is installed. In automatic start mode,parameters can be set via the HMI touch screen, enabling automatic execution of braking distance, stopping parameters, acceleration, constant speed, deceleration, and automatic parking.
5. PLC-Based Hoist Control & RedundancyUsing Siemens PLC S7 for hoisting process control, the system ensures crossmonitoringand redundant safety protection. The PLC system includes DUDO, AVAO, high-speed counters, and communication functions with spare capacity.
Safety functions include:
Redundant safety circuits via PIC and relays. Full-range speed monitoring: Pre-alarm if actual speed exceeds set speed by 8%. Safety braking if speed exceeds 15% in constant speed section or 10% in deceleration section. Overwind protection: safety braking at 0.5m overwind. Brakeshoe wear and spring fatigue protection. Hardware and software interlock with the signaling system. Comprehensive PLC software fault protection.
Additional protections include:
Overcurrent, overvoltage, and undervoltage protection. Inverter input/output phase loss protection. Depth indicator shaft break protection. Backup protection for deceleration points.Shaft collar overspeed protection. Reverse direction protection. Secondary brake release protection. Overspeed protection in constant speed and deceleration sections.Start-up and signal interlock protection. Automatic self-lock and directional switching. Safety circuit achieved through both PLC internal and external AC loops.
Indicators, Instruments & Controls:
The console is equipped with indicator lights, instruments, selection switches, buttons, and audio-visual alarms to meet hoist operation requirements.Instrument displays include: hoisting speed, motor voltage, motor current, brake oil pressure, adjustable brake current, etc. Indicator lights include: hoist operating status, signaling status, and safety status.Switches & buttons include: operation mode selector switch, overwind reset switch, self-locking emergency brake button, and semiautomaticstart button.
