Power-limiting heating cables (VPL) can be used for freeze protection and process temperature maintenance requiring high power output and/or high temperature exposure. Operating to voltages up to 480 V, power-limitingheating cables can provide:
- Temperature maintenance up to 235°C;
- Exposure temperature up to 260°C;
- Circuit lengths up to 450 m.
Power-limiting cables are formed by a coiled resistor alloy heating element wrapped around two parallel conductors. At a fixed distance the insulation is removed from one of the conductors and the process is repeated, removing the insulation from the other conductor. The distance between contact points forms the heating zone length.
High Temperature Power Limiting Heating Cables
How it works
The positive temperature coefficient (PTC) of the alloy resistor heating element allows an adaptation of power in relation to the temperature of the system on which the heating cable is installed.
As the temperature surrounding the cable decreases, the resistance of the heating element reduces, resulting in an increase of power output. As the temperature rises, this resistance increases generating a limitation of the power output.
This effect allows the power-limiting cable to be overlapped once, since the power-output of the heating element is reduced at cross-over points.
Benefits
Reduced heating cable quantity
Power-limiting heating cables provide high power-output at elevated temperatures which can reduce the number of heating cable runs required.
1. Lower start-up current
The relatively flat power temperature curve ensures a lower start-up current.
2. Longer circuit lengths
When operating at higher voltages, the maximum circuit lengths increase and therefore the number of circuits and use of junction boxes, power cables and other components can be reduced.
3. Easy Installation
Power-limiting heating cables may be cut-to-length on-site according to heating zone length and can be overlapped once at valves, flanges and instruments without the risk of local overheating.
4. Limited maximum generated temperatures
By their specific power-limiting technology, VPL heating cables offer the possibility of stabilised design T-ratings as specified by European norm EN 60079-30-2.
Applications
Typical applications include needs for high maintain temperatures or continuous high exposure temperatures in all industrial applications.
Power-limiting cables are formed by a coiled resistor alloy heating element wrapped around two parallel conductors. At a fixed distance the insulation is removed from one of the conductors and the process is repeated, removing the insulation from the other conductor. The distance between contact points forms the heating zone length.
