| 摘要 |
The protective circuit is used in a switching arrangement for protecting an electric motor against thermal overload, and of the type including a heating resistor in the motor supply circuit, a temperature sensing resistor, having a highly temperature-dependent resistance characteristic, in heat transfer contact with the heating resistor and a motor cut-off control means connected to the temperature sensitive resistor to provide a signal voltage for disconnecting the motor from its source of potential upon thermal overloading of the motor. The heating resistor has a thermal behavior simulating the thermal behavior of the motor to be protected. A bias voltage is applied to the input of an amplifier of the cut-off control means, and this bias voltage can be set on a potentiometer and is influenced by an additional temperature-dependent resistor to compensate the room temperature at the location of the switching arrangement. The arrangement may be used with either a direct current motor supply, a single phase AC motor supply, or a polyphase AC motor supply. |
