**5.5. IM energized from inverters**

The last experiment examined two-pole IM with 2 broken bars energized from inverters. Two PWM open-loop inverters were used. The measurements were made at low inertia and at a stable motor load.

In the first measurement, an inverter was properly rated. In this case, the results correspond to the results for IMs energized from line. The MCS *aAPL* = *aAPH* and time course of AM and PM was completely opposite.

**Figure 11.** Inverter fed IM, low DC-link and overloaded, low inertia, 75% of full load, MCS, time course of amplitude and phase demodulated current, PM delays *-ϕ* behind AM.

In the second measurement another inverter was not properly rated and its DC-link voltage was only 400V. IM was fed by lower voltage apps. 185V and therefore was overloaded. In this case the MCS *aAPL aAPH* appeared (the same phenomenon which can appear at great inertia). The demodulation detected PM delay *-* behind AM -see Fig.11 and validated the explanation of *aAPL* > *aAPH* in Fig.4., and also the correctness of (6).

This phenomenon of PM delay behind AM at low inertia appears when an AC source is not properly dimensioned, its feeding voltage is lower than nominal voltage and therefore it is not able to fully excite IM.

It can be concluded that continual increasing of *aAPL* above *aAPH* (out of the range of possible *aAPL* and *aAPH* variations± 2.5dB) generally means, that IM working conditions are out of the normal.
