Overheated metal parts can act as an ignition source in electrotechnical devices. In the glow wire test, the glowing wire loop serves as such an ignition source. This test method is used to examine the fire safety properties of products when during their use or in the event of a fault, parts that are heated or glowing can be considered as short-term ignition sources.
High temperatures are to be expected in electrical items, their assemblies and parts due to loose connections and bad contacts. Attention must also be paid to the risk of fire emanating from textile seat covers, tablecloths or
curtains, for example after exposure to cigarette burns.
For this reason, prototypes of all articles that can cause danger through contact with ignition sources should be subjected to the glow-wire test.

Heating the glow wire loop

The prescribed maximum test temperature of 960 ° C is reached by the glow wire loop at a current of around 130 A. This current is supplied by a high-current transformer with a secondary winding with a few turns of copper wire.
A variable transformer with a rotary knob is connected upstream of the high-current transformer to set the current intensity and thus the temperature of the glow wire loop.

Working principle

The glow wire loop simulates a strongly heated fire source. The adjustable temperature is measured using a jacket thermo- couple. For testing, the sample is moved to the glow wire through the carriage with a rail system. The time the sample remains on the filament can be variably set using a timer.
During the test, the car is pulled against the wire with a force of approx. 1 N using weights. After the test time has elapsed, the carriage with the sample is automatically driven back.