What are control cables? Structure and classifications of control cables

1.1 What are control cables?

Control cables are specialized electrical cables designed to transmit control signals to machinery and electronic systems. They are used for both internal and external wiring, connecting equipment ranging from machines and production lines to sensors and actuators. Control signals instruct the receiving device to perform specific functions.

Serving as the communication link between sensors, switches, controllers, and operating devices, control cables enable automation systems to react and adjust in real time. As industries move toward smarter and more connected operations, control cables are evolving to support higher data transmission rates and greater durability.

These cables are engineered to withstand harsh environmental conditions such as extreme temperatures, humidity, and mechanical stress. They are widely used in industrial automation, robotics, transportation, and building management systems. Their construction ensures stable signal transmission, high safety, and compliance with industry standards.

The role of control cables continues to grow in importance as they ensure uninterrupted communication, minimize interference, and maintain smooth operation in complex industrial environments.

Learn the basics about electrical cables: Structure, characteristics, and applications

1.2 Basic structure of control cables

The construction of a control cable typically consists of the following components: conductor, insulation, shielding, outer sheath, and armor.

• Conductor: The most critical part of the cable, commonly made of copper or aluminum. Depending on the application, it may be a single-core or multi-core structure.
• Insulation: Provides electrical isolation between the conductors and from the external environment. Common insulation materials include PVC and XLPE.
• Shielding: Protects against EMI from external sources and prevents emitted interference from affecting surrounding equipment. Common shielding materials include: Cu braid, Cu tape, Alu-PET foil
• Outer sheath: Protects the cable from mechanical impact, chemical, and environmental factors. Frequently used materials include PVC, rubber, or PUR depending on the application conditions.
• Armour: Enhances mechanical strength, impact resistance, and external force protection. Typically made from steel tape or steel wire, depending on the required durability.

Control cables play a crucial role in most systems that require high levels of accuracy and safety. Below are the most common application sectors:

Industrial automation: From production lines to robotic systems, control cables connect sensors, motors, and PLCs to ensure every movement occurs at the right time. They are designed to withstand continuous motion, vibration, and electromagnetic interference.

Building Management Systems (BMS) and construction: In both commercial and residential buildings, control cables are used for lighting control, elevators, HVAC systems, and fire alarm systems. They help maintain stable operation and ensure the safety of facilities.

Internal wiring of machinery and equipment: Inside machinery such as CNC machines, conveyors, and packaging equipment, control cables manage functions like start/stop, speed control, or emergency shutdown. Highly flexible cables are used when components are subject to frequent motion.

Renewable energy: Control cables play an essential role in solar farms and wind turbines by connecting sensors, controllers, and power converters. They support real-time monitoring, precise adjustments, and overall system optimization. For example: Offshore wind farms require durable control cables capable of withstanding harsh marine environments to ensure continuous operation and compliance with safety standards.

There are several types of electrical cables that are closely associated with control cables and sometimes used interchangeably. However, distinct differences exist between them.

3.1 Control vs signal vs instrumentation cables

Signal cables: include coaxial cables, twisted pair cables, and fiber optic cables. They are primarily used for data transmission, so they require shielding to protect against EMI.

Control cables: Similar to signal cables, control cables also carry control signals. However, they are not always shielded. They are mainly used to transmit command signals to devices within automation systems.

Instrumentation cables: Designed for transmitting measurement and monitoring signals, these cables require superior shielding against EMI and crosstalk.

In many cases, the terms “control cable” and “instrumentation cable” may be used interchangeably, as their functions are closely related.

Learn about solutions for preventing crosstalk in electrical cables

3.2 Control cables vs power cables

Power cables are responsible for transmitting electrical energy in machinery, industrial facilities, and equipment. They are also used to supply power to buildings and to distribute electricity in power plants and substations. This type of cable may also be called connection cable, supply cable, or energy cable.

Although both power and control cables are widely used in industrial, commercial, and residential environments, they differ significantly:

Operating voltage: Power cables typically handle higher voltages, starting from 0.6/1 kV and above, while control cables operate at lower voltage levels, usually 300/450/600/750 V.

Insulation: Because power cables transmit high energy loads, they require strong and durable jackets that can withstand corrosion, temperature changes, and harsh external conditions. Control cables, on the other hand, generally do not need such heavy-duty sheathing and commonly use standard PVC insulation.

4.1 PVC control cables

PVC control cables are the most common choice for general industrial applications.

Properties: Flexible, easy to install, cost-effective.

Applications: Suitable for dry indoor environments, commonly used in standard industrial production lines.

Advantages: Operating temperature range from approx. -30°C to +70°C, excellent electrical insulation, and moderate mechanical strength.

4.2 PUR and TPE control cables

PUR and TPE control cables are well-known for their exceptional flexibility and high elasticity.

Properties: Highly flexible, abrasion resistance, resistant to oils, chemicals, and weather conditions.

Applications: Ideal for dynamic applications such as robotic systems, drag chain, and outdoor environments.

Advantages: Outstanding tear resistance, long service life under harsh operating conditions, UV resistance, and wide operating temperature ranges: -55°C to +80°C (PUR), -50°C to +100°C (TPE).

4.3 Halogen-free control cables

Properties: Halogen-free material, reducing smoke and toxic gas emissions in event of fire.

Applications: Suitable for buildings and facilities requiring a high level of fire safety, such as steel plants, metallurgy

Advantages: Enhanced safety for people and equipment, flame-retardant, and maintains solid mechanical performance.

FRNC, HFFR, LS0H, LSZH: Learn the differences between halogen-free cable types

4.6 Intrinsically Safe control cables

Intrinsic safety is a protection technique designed to ensure the safe operation of electrical and electronic equipment in hazardous areas, where any potential ignition source must be completely eliminated.

Essentially, electrical cables with a sealed construction can be considered intrinsically safe in certain applications if they are protected against mechanical damage, external electrical or magnetic fields (EMI), and isolated from non-intrinsically safe circuits. Junctions and switches represent potential ignition points in these environments and circuits.

Intrinsically safe control cables are typically blue to identify potential electrical hazards and the need for special handling measures. HELUKABEL's three intrinsically safe cable products include: OZ-BL ( 14001 ), OZ-BL-CY ( 14028 ), OB-BL-PAAR-CY ( 14077 ).