Ground surface heating system - uses buried mats of woven resistance material supplied by automatically adjusted DC voltage

摘要

The heating mats are laid in the ground in two parallel strips connected in series and fed with a d.c. voltage. The d.c. voltage is derived from the a.c. mains by a full-wave rectifier bridge fed via a thyristor control circuit. The heating effect w.r.t. the ambient temp. is measured by a sensor immersed in a liq. inside a tube surrounded by a sleeve of the heating material. The sleeve is supplied with l.v. d.c. via a voltage divider. The sensor output is fed to a control circuit which adjusts the firing angle of the thyristors to achieve the required heating level. The heating material used is woven and has the trade mark: ISOMUVOTHERM.