| 摘要 |
<p>21-DSX-2535 PROGRAMMABLE OVERLOAD CIRCUIT Disclosed is an overload protective circuit for an electric motor which is adapted to monitor and track motor temperature as a function of an operating parameter, namely armature current. The motor's armature current is sensed and converted to a multi-bit digital signal which is used to address a programmable read only memory (PROM) which has been pre-programmed with discrete digital values of temperature for a plurality of armature currents for the motor being protected. The digital address signal for the armature motor current is periodically updated at a relatively rapid rate and depending upon the armature current sensed, multi-bit temperature values are outputted from the PROM to a digital latch which operates a relatively slower rate to output another address back to the PROM to as to predict what the temperature will be at the next time increment based on the present current value and the present temperature. When predetermined temperature levels are reached, two bits of the PROM's output are respectively adapted to provide an alarm signal, and then a subsequent trip signal which is adapted to deenergize the motor.</p> |
