Overhead traveling cranes are designed to facilitate the lifting and transportation of loads in industrial settings. The electrical systems in these cranes differ significantly from household electrical systems and require high reliability and safety. This article will explore the main components of crane electrical systems and their functions.
1. Basics of Electrical Systems
Industrial electrical systems are typically designed as three-phase systems, which means they are powered through three separate cables. The system configuration can be customized as follows:
- 3-phase cables
- 3-phase + 1 ground
- 3-phase + 1 ground + 1 neutral
- Neutral: The line that completes the electrical circuit. It ensures the proper functioning of devices by providing a return path for the current.
- Grounding: Directs electrical leakage safely to the ground, protecting both people and equipment from electrical hazards.
2. Voltage and Frequency (Hz)
Voltage: Refers to the force of the electrical current on devices. Higher voltage generally increases system costs but is necessary for lifting heavier or larger loads.
Frequency (Hz): Indicates the number of oscillations of the electrical current per second. While 50 Hz is standard in Turkey, 60 Hz systems are also used based on customer requirements. Frequency affects the speed of crane motors; adjusting it helps optimize motor performance.
3. Busbar System
Busbar systems supply the current needed by the cranes and are available in different amperage levels (e.g., 40, 63, 80, 100, 125, 160, 200). These can be installed along both the bridge and the hall length. For bridge installations, the busbar length is calculated as axle span x 3, with three busbar lines and three current collectors provided.
4. C Rail System and Festoon Cables
Different types of C rail systems and festoon cables are used for various load capacities:
- 28’ C rail system with festoon cables: Suitable for cranes with a capacity of 16 tons or less due to the lighter cables.
- 40’ C rail system with festoon cables: Used for cranes with a capacity of 20 tons or more due to heavier cables.
- NPI 80 system: Also used for cranes with a capacity of 20 tons or more for better cable management.
5. Wired and Remote Control Systems
- Wired Control: Available in two types:
- Attached to the trolley
- Fixed on the C rail according to the bridge length
Both types can be adapted for single-speed/double-speed and customized for specific movement options.
- Remote Control: Comprises a receiver fixed to the crane’s control panel and a transmitter held by the operator for movement control. It also supports single-speed/double-speed and movement options as required.
6. Accessories and Components
Fuses: Protect circuits by breaking the connection during short circuits or overcurrent, ensuring system safety.
Contactors: Manage current between the crane motors and facilitate power transfer during control operations.
Inverters: Control motor speed and provide ramping functions to slow down gradually when stopping.
Relays: Manage control signals and protect motors from overload and low voltage.
Junction Box: Protects electrical connection points and is commonly used at cable junctions in crane systems.
Isolation Transformer: Isolates the circuit from the power grid, enhancing system safety.
Terminal Blocks: Securely connect wires within the electrical panel.
Braking Resistor: Helps stop motors quickly, especially when lowering loads.
Emergency Stop Contactor: Halts the system during emergencies for safety.
PLC (Programmable Logic Controller): Automates crane operations and ensures specific commands are carried out.
Load Cell: Measures the weight of the load and transmits data to the control panel.
Compact Circuit Breaker: Protects circuits against overcurrent and manages electrical loads in the system.
Indicators: Display the operational status of the crane.
7. Difference Between AC and DC Current
AC (Alternating Current): The current that changes direction periodically and is commonly used in crane systems due to lower power loss over long distances.
DC (Direct Current): Provides current in a single direction. Although less common, it is used in specific applications.
These core components ensure the safe, efficient, and high-performance operation of overhead traveling cranes. Proper selection of these components is essential for both functional and economic benefits.
