Method for obtaining an indication, in particular a starting indication of a possible faulty load condition of a multi-phase electric motor

Abstract

According to the invention, the electric motor is electrically commutated with the aid of circuitry, in which the phase current experiences a zero crossing at certain time points per motor phase. Owing to the inductive load portion, the time of said zero crossing of a phase current occurs at different times to the time of the zero crossing that would arise with purely ohmic loads. Without a faulty load condition, the time of said zero crossing is within an expected value range (e.g., expected time window) which can be determined by the circuitry, the ambient conditions and by diverse motor parameters. According to the method, during occurrence of the high-side and / or low-side phase connection predetermined in the circuitry, it is determined whether and when the current through the switched-on high-side or low-side switch becomes greater or smaller than a predeterminable threshold, in a particular case in the vicinity of the zero crossing, wherein said time measurement can extend in the case of a PWM control, if required, over one or more PWM cycles.

Description

[0001] This patent application claims priority from three German patent applications 10 2014 212 586.3, 10 2014 212 572.3 and 102014 212 626.6, all filed on June 30, 2014, which are hereby incorporated by reference into the subject matter of this patent application . technical field [0002] The invention relates to a method for obtaining an indication, in particular starting an indication, of a possible faulty load situation of a polyphase motor. Background technique [0003] Faulty load conditions in the motor are particularly critical when a short circuit occurs. Such a short circuit is usually detected by means of a voltage drop on the drain-source path of a driver transistor internal or external to the control unit via which the motor or other load is controlled. These voltage drops are usually assessed individually, ie on each phase of the motor. If the metrologically detected current is greater than the maximum permissible operating current, this means an external s...

AI Technical Summary

Problems solved by technology

But the power transistor can still heat up to such an extent in this case that damage is caused, which happens so quickly that even the overheating detection device cannot provide sufficient protection due to its time delay

Images