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.
Transient Measurement
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.
