| 摘要 |
In a device for monitoring the heating of an electric motor (1), the motor current from a current transformer (5) is fed via a squaring stage (6) to an analog-digital converter (7) as a value which is proportional to the square of the current, and converted there into a digital quantity. This digital quantity, and the current-independent adjustable digital quantity of an analog-digital converter (11), are input to a computer (8) according to control commands of a step switching mechanism (10), and the computer is controlled by the step switching mechanism (10) such that the digital quantity which is proportional to the square of the current is multiplied by the current-independent digital quantity, another digital quantity proportional to the square of the current is added to the product, and this cycle is repeated after the step switching mechanism is reset, until an output quantity which appears at the output of the computer (8) makes a limit stage (9) react, and thus interrupts the motor current circuit by a release device (4). In this way, the motor can be monitored for impermissible heating, in continuous operation or load alternation. If a squaring and storing computer is used, the squaring stage and a separate memory can be omitted. <IMAGE> |
