Thermostat safety cut=out for electric kettles etc. - inhibits reconnection until temp. has fallen and power is switched off until positive action is taken

摘要

The thermostat is used in electrical heating equipment, typically electric kettles, where once a desired temp. has been reached, the power should not be re-connected to the element without a decisive action by the user. Power to the element flows through contacts which are held together by a bi-metallic strip (5) until the temperature exceeds the required switch-off level. When the main contact is broken, a much smaller current continues to flow through a resistive bridge across the contacts. The power dissipated by the resistive bridge provides local heating which ensures that the bi-metallic strip keeps the contacts apart until the current source is broken. The bridge may be a resistive paste (9) coating a pin (4) alongside the strip, or a plate under the strip.