The MAVO-TCM expands the scope of functions included with the
MAVOWATT 45 to include
two special facilities for mains power measuring technology:
• brief transient events can be captured which occur in alternating or direct current power supply lines, as well as at power consumers connected to them.
• the instrument is capable of acquiring measured quantities for power and energy analysis at frequency converter outputs.
Voltage transients with a duration of at least 20 µs can be acquired, and measured at levels of up to 1500 Vs.
Trigger conditions for events recording are derived from a comparison of the absolute level of a sampled value and the selected trigger level (Up or lp). A rate of change trigger is active as well. The sampling interval (20 us to 640 us) and the pre-trigger can also be adjusted.
The Event display mode can be used for recording rapidly occurring, successive events. This allows for recording of up to 40 events per second listed in the order in which they occur along with time stamp, cause of triggering, measured quantity and sampled or rate-of-change measured value.
Measurements at Frequency Converters
Modern frequency converters used for controlling electric motor speed usually have a high frequency square-wave output voltage which is pulse-width modulated via motor frequency.
This type of measurement signal requires a special measuring process, by means of which the converter switching
frequency is filtered out, and the effective modulation frequency at the motor (fundamental frequency) is determined.
• Switching frequency must be greater than 1.2 kHz, and fundamental frequency within a range 10 to 100 Hz.
• Motor current is acquired in an electrically isolated fashion, e.g. with a clip-on ammeter.