Fluke 438-II Three-Phase Power Quality and Motor Analyzer


This Power Quality and Motor Analyzer adds key mechanical measurement capabilities for electric motors to the cutting-edge power quality analysis functions of the Fluke 430 Series II Power Quality Analyzers. Quickly and easily measure and analyze key electrical and mechanical performance parameters such as power, harmonics, motor speed, unbalance, torque and mechanical power without the use of mechanical sensors.

SKU: 438-II


Fluke 438-II Offers

The ideal portable tool for motor analysis testing, the 438-II can help locate, prevent, predict and troubleshoot power quality problems in three-phase and single-phase power distribution systems, while giving technicians the mechanical and electrical information they need to evaluate motor performance effectively.


Measure key parameters on direct-on-line motors including torque, RPM, mechanical power and motor efficiency
Perform dynamic motor analysis by plotting of motor de-rating factor against load according to NEMA guidelines
Calculate mechanical power and efficiency without the need of mechanical sensors, just connect to the input conductors and you’re ready to go
Measure electrical power parameters such as voltage, current, power, apparent power, power factor, harmonic distortion and unbalance to identify characteristics that impact motor efficiency
Identify power quality issues such as dips, swells, transients, harmonics and unbalance
PowerWave data technology captures fast RMS data, and shows half-cycle averages and waveforms to characterize electrical system dynamics (generator start-ups, UPS switching etc.)
Waveform capture function captures 100/120 cycles (50/60 Hz) of each event detected event, in all modes, without set-up
Automatic transient mode captures waveform data at 200 kS/s on all phases simultaneously up to 6 k


Industrial Manufacturing Plants
Electrical Contracting and Consulting
Commercial and Institutional Facility Management Departments

Fluke 438-II mechanical metering functions

Motor torque
Calculates the amount of rotational force (displayed
in lb.ft or Nm) developed by a motor and transmitted
to a driven mechanical load. The motor torque
is the single most critical variable that characterizes
the instantaneous mechanical performance of
rotating equipment driven by electric motors.

Motor speed
Provides the instantaneous motor shaft rotational
speed. Combined with the motor torque, motor
speed provides a snapshot of the mechanical performance
of rotating equipment driven by electric

Motor mechanical load
Measures the actual mechanical power (displayed
in hp or kW) produced by motors and provides a
direct link to overloading conditions without simply
basing it on the motor current.

Motor efficiency
Shows the effectiveness of each motor within a
machine, assembly line, plant, and/or facility in
converting electric power to useful mechanical
work. By properly aggregating the efficiencies of
a population of motors the total (aggregate) efficiency
can be estimated. Comparisons to expected
motor efficiencies at observed operating conditions
can help quantify the cost associated with motor
energy inefficiency.

How it works
Using proprietary algorithms, the Fluke 438-II
Power Quality and Motor Analyzer uses three phase
current and voltage waveforms to calculate
motor torque, speed, load and efficiency at a
1 second update rate. The motor air gap field,
as observed via the voltage/current waveforms,
provides the basis for the measurements. Mechanical
sensors and intrusive no-load motor testing is
not required, making it faster than ever to analyze
overall electric motor performance.

Simply hookup the voltage measurement leads and
flexible current probes to the service supplying the

Input details of the motor from the rating plate
including rated power, rated speed and motor type
from either NEMA or IEC classifications.

Note: Measurement units can be set to local
requirements hp/kW, lb ft/Nm etc.

3 Fluke Corporation Fluke 438-II Power Quality and Motor Analyzer Electrical motor analysis

The Fluke 438-II provides a complete breakdown
of electrical parameters. Prior to beginning motor
analysis, it’s recommended to make base line
power quality measurements to assess the state of
harmonics and unbalance on the electrical service
output as these two properties can have a serious
negative impact, on motor performance.

When in Motor Analysis mode, results are summarized
for electrical performance, mechanical
performance and derating (according to NEMA

The easy to understand four-level color severity
scale indicates motor performance in relation to
the recommended electrical parameter levels
including rated power, power factor, unbalance
and harmonics.

For mechanical power you can instantly view
the mechanical output power along with motor
torque and speed. The mechanical output power
is instantly compared with electrical power to
provide you with live efficiency measurements.
With this feature you can easily measure machine
performance during each operation cycle.

The NEMA derating screen is updated as the load
and the electrical conditions change, and each
new measurement is plotted on the tolerance
graph as a “+”. In this example we can see that
motor is within tolerance but is close to the service
factor. This indicates that there may be a
need for power quality mitigation, motor maintenance
or some other performance improving
adjustment. By frequently performing these tests
over time, known benchmarks and performance
trends can be created, enabling informed
maintenance investment decisions.

Fluke 438-II Specifications

Motor Measurment
Default Limit

Mechanical motor Power
0.7 kW to 746 kW
1 hp to 1000 hp
0.1 kW
100 % = rated power
100 % = rated power

0 Nm to 10 000 Nm
0 lb ft to 10 000 lb ft
0.1 Nm
0.1lb ft
100 % = rated torque
100 % = rated torque

0 rpm to 3600 rpm
1 rpm
100 % = rated rpm

0 % to 100 %
0.10 %

Unbalance (NEMA)
0 % to 100 %
0.10 %

Harmonics Voltage Factor (NEMA)
0 to 0.20

Unbalance Derating Factor
0.7 to 1.0

Harmonics Derating Factor
0.7 to 1.0

Total NEMA Derating Factor
0.5 to 1.0

?Add 5 % error when selecting Motor design type Other

Specification valid for Motor Power > 30 % of rated power

Specification valid at stable operating temperature. Run the motor for at least 1 hour at full load

(2-3 hours if the motor is 50 HP or higher) to obtain stable temperature.


Supports motor design types NEMA A, B, C, D & E and IEC type H and N.
Rated torque is calculated from rated power and rated speed.
Update rate of Motor Measurements is 1x per second.
Default Trend duration is 1 week.
Click here for complete specifications on the Fluke 438-II


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