Tipping point (asynchronous machine)
The tipping point is the point on the torque-speed characteristic of an asynchronous machine (ASM) at which it develops its maximum torque, the breakdown torque . It is also the highest point on the torque / speed characteristic. If the asynchronous machine is subjected to a greater motor or generator load than the breakdown torque during operation, it stops or spins: it "tips over". The tipping point is in the machine's overload range and should therefore only be reached for a short time. In the overload range, the machine heats up excessively.
It will be in 50 Hz operation , which means that the following formulas can be assumed for the data of the breakdown point : The breakdown torque depends on the square of the ratio of stator voltage to stator voltage frequency. A higher stator current flows into the ASM when there is a high voltage and a low frequency. The level of the stator current determines the level of the rotor current. The torque is proportional to the product of the two.
Overturning moment
The breakdown torque is the maximum torque available for a short time .
Overturning slip
The perpendicular from the tipping point to the speed axis marks the tipping slip .
Kloß formula
The Kloß formula is an approximation equation for asynchronous machines to determine the torque as a function of the speed or the slip.
Explanation of the individual symbols
variable | meaning |
---|---|
Asynchronous machine slip | |
Tilting slip of the asynchronous machine | |
Moment of the asynchronous machine | |
Breakdown moment of the asynchronous machine | |
Stator resistance of the asynchronous machine | |
Stator reactance of the asynchronous machine | |
related rotor resistance of the asynchronous machine | |
related rotor impedance of the asynchronous machine | |
Main reactance of the asynchronous machine | |
Scatter factor of the asynchronous machine: | |
Number of strands, for the asynchronous machine 3 | |
Phase voltage of the asynchronous machine | |
Speed of the asynchronous machine with vanishing moment of resistance in |