素線切れビニルコードの着火電流と流入エネルギー

抄録

Polyvinyl chloride covered cords which have many excellent advantages in electrical and mechanical natures, are widely used for lead wires connecting the electrical apparatus. However, when a part of element wires of polyvinyl chloride covered cords are cut by any repeated force, such as bend and twist ones, even if rated current applied to the polyvinyl chloride covered cords having disconnected element wires (PCC), it results in an over current for the residual element wires. As a result, firing phenomena of PCC are possible by an abnormal generated heat caused by the over current in the element wires under the normal operating condition.
In order to investigate the firing phenomena of PCC under the normal operation, experimental and theoretical studies on the firing current and energy input of PCC have been carried out using a model PCC which is especially devised in consideration of the hardest working condition, and is composed of only an element wire of certain lengths between both ends.
The results obtained for the firing phenomena of PCC according to the over current are shown as follows:
(1) Firing current and time ranges of the model PCC are from about 60 to 1,000 sec. for applied current from about 10 to 30 A.
(2) Firing process of PCC have next two ones; first, the temperature rise up to about 100°C takes place owing to the abnormal generated heat caused by the over current in the element wire, thereafter, instantaneously generated one produced by the element wire explosion forced the polyvinyl chloride covering to about 550°C, then it comes to fire.
(3) Firing heats of PCC are ranged from about 50 to 800% of the contained one in the polyvinyl chloride covering at firing temperature.