The PM3000 Power Analyzer has been designed for a range
of measurement solutions...
Click on a solution to learn more...
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PM3000 Motors and Drives
A PWM (Pulse Width Modulated) drive, used with an ac motor, is the economical way
of producing a motor system with variable speed. With the advent of low cost power
semiconductors capable of high speed switching, the variable voltage and frequency
control required by the ac motor is easily achieved using the technique of Pulse
Width Modulation.
Typical PWM drive
Motor Output Measurements
The Voltech PM3000A Power Analyzer is equipped with auxiliary inputs that you can
connect to torque and speed transducers, allowing the PM3000 to directly read and
display
· The rotation speed of the motor
· The (mechanical) motor output power
= Torque (Nm) * Speed (radians / sec)
= Torque (Nm) * Speed (rpm) * (p / 30)/p>
Motor Output Measurements
The output waveform of a PWM drive is a complex mixture of high and low frequency
components, which most power analyzers find difficult to measure accurately. This
because they either measure at high frequencies, in which case the low frequency
content of the waveform is lost, or they filter the waveform to measure at low frequencies,
in which case the high frequency data is lost.
A particular difficulty is measuring the total power, which must be done by sampling
at a high frequency (to include the high frequency content of the waveform), but
over an integral number of cycles of the motor frequency.
The PM3000 overcomes these measurement problems
by using a special operating mode for PWM output measurements. The data is sampled
at high speed, and parameters such as the total Vrms and Watts are computed in real
time. At the same time, the samples are digitally filtered to provide the low frequency
measurements such as the fundamental voltage and current, and a measurement of the
output frequency.
Input Measurements
A PWM drive does not always present a constant load, and therefore the current taken
from the supply will be modulated by components of the output frequency. This complex
waveform can present problems to many power analyzers.
The PM3000 has a special operating mode for measuring the input power to a PWM drive.
In this mode, measurements are synchronised to the ac line frequency, but made over
a user specified interval of between 1 and 10 seconds, which is an integral number
of cycles of the output waveform.
Ideal for measurements on three-phase power supplies, invertors and UPS the versatile
PM3000A power analyzer provides reliable data at the touch of a button.
As well as power, volts, amps, VA, VAr and power factor the PM3000A measures harmonics
and THD (including a pre-compliance EN61000-3-2/2 harmonics and flicker option).
PC software allows all measurements to be viewed graphically and stored on a pc
for analysis and reports.
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PM3000 Single Phase Measurements
At first glance, making single phase measurements should be simple. Every wall socket
is a single ac source. Every household appliance connected to the mains draws on
this single phase ac current.
If the load is a simple resistive load such as a heater that is on continuously,
then making measurements on that current is straightforward. However, more and more
equipment now draws very complex current from the ac supply, so measurement becomes
more challenging.
Sometimes the current is drawn in bursts, sometimes it can be highly distorted and
have a high crest factor. Sometimes measurements need to be made in the presence
of common mode. Making accurate measurements in these situations requires care.
The PM3000 is just one of Voltech’s power analyzer range that is ideally suited
to making single phase measurements.
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PM3000 Power Transformers
Power transformers are characterized under open-circuit and short-circuit conditions.
Open circuit, the power factor of the transformer is close to zero (<0.01), which
demands very low phase error of the power analyzer.
The analog design of the PM3000ACE ensures that its voltage and current channels
are carefully matched, providing great performance at low power factors.
Measurements
- Watts, Vrms, Vrmn, Arms, VA, VAr, Apk, Harmonics, THD, Inrush. K-factor and corrected
power to IEEE and IEC standards
Advantages
- Accurate at low power factors
- Simultaneous measurement of rms and mean voltage as required by IEC76 and IEEEC57
See it in Action
PM3000 Three-Phase Measurements
Although single-phase electricity is used to supply common domestic and office electrical
appliances, three-phase alternating current (ac) systems are almost universally
used to distribute electrical power and to supply electricity directly to higher
power equipment.
Three-phase electricity consists of three ac voltages of identical frequency and
similar amplitude. Each ac voltage ‘phase’ is separated by 120° from the other.
Power is measured in ac systems using wattmeters. A modern digital sampling wattmeter,
such as any of the Voltech PM series, multiplies instantaneous samples of voltage
and current together to calculate instantaneous watts and then takes an average
of the instantaneous watts over one cycle to display the true power. A wattmeter
will provide accurate measurements of true power, apparent power, volt-amperes reactive,
power factor, harmonics and many others over a broad range of wave shapes, frequencies
and power factor.
By sampling the three-phase waveform simultaneously on all wattmeter channels the
PM3000A is able to make measurements in STAR (3-phase, 4-wire) or DELTA (3-phase,
3-wire) configuration or calculate STAR voltages and currents when connected in
the DELTA configuration or vice-versa.