| 摘要 |
In an intrinsically safe, non self-resetting temperature limiter, a bistable relay (RY) is used, on the one hand, to switch off and lock the burner control unit (A) when the limiting temperature is exceeded and, on the other hand, is used with its inductor connected to a rectifier circuit (D1, C2) to generate an activation voltage (Ea) for the burner control unit (A). In normal operation, the relay carries a power pulse current which does not cause the relay to operate, but does generate the activation voltage. The high-frequency impulse voltage is generated by a relaxation oscillator (OS) in which an overtemperature-sensitive micro-switch (quick-make-quick-break switch) (HL) is closed (switched on, turned on) in such a way that when the overtemperature is reached the oscillator oscillations break off and the relay (RY) is fed a DC current which causes the said relay to operate. <IMAGE>
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