Application Note

5 Fluke Corporation Multimeter measurements on variable frequency drives using the new Fluke 289 DMM
Output current and frequency
(motor speed)
With the large dot matrix display on the 289
multimeter, it is possible to display both the ac
current reading and its’ associated frequency
simultaneously, allowing the technician or installer
to see both the load current and motor speed at
the same time, in the same display.
Transformer type clamp (i200, i400,
80i-400, 80i-600A, i800)
1. Regardless of the type of clamp used, check
to insure that all phase current readings are
within 5% of each other for proper balance
2. Connect the clamp to the 289’s common and
400 mA input jacks.
3. Select the mA/A ac function. If you want to take
advantage of the 289’s dual display, then select
MENU then Hz.
4. Place the clamp around each of the output
phase cables in succession, recording each of
the readings as they are taken or save them to
internal memory for later use.
Since these clamps output 1
milliamp per amp, the milliamp
readings shown on the 289
display are the actual phase
current reading in amps as
well as the frequency of the ac
current signal.
Hall Effect type (AC/DC) clamp
(i410, i-1010)
1. Connect the clamp to the 289’s
common and V/Ω input jacks.
2. Select the 289’s mVac
voltage function for current
measurements up to 500 amps.
3. Select MENU then (LPF+Hz)
to enable the low pass filter
and the Hz function. This will allow the
meter to reject all of the high frequency noise
generated by the drive controller. Once the low
pass filter has been enabled the meter is now
in manual range mode.
4. Since the lowest range on the 289 is 50.000
mVac push the range button once to place
the meter in the 500.00 mVac range if the
drive current will exceed 50 amps for the
measurement.
5. Place the clamp around each of the output
supply phase cables in succession, recording
each of the readings as they are taken or again
save to the 289’s internal memory. Since these
clamps output 1 millivolt per amp, the millivolt
readings shown on the 289
display are the actual phase
current reading in amps.
Caption?
Phase current reading + motor speed using i1010 clamp
Fluke Corporation
PO Box 9090, Everett, WA USA 98206
Fluke Europe B.V.
PO Box 1186, 5602 BD
Eindhoven, The Netherlands
For more information call:
In the U.S.A. [phone] or
Fax [phone]
In Europe/M-East/Africa [phone]
or Fax [phone]
In Canada (800)-36-FLUKE or
Fax [phone]
From other countries [phone] or
Fax [phone]
Web access: http://www.fluke.com
©2008 Fluke Corporation. Specifications subject
to change without notice. Printed in U.S.A.
7/2008 3291974 A-EN-N Rev A
Fluke. Keeping your world
up and running.
®
DC Bus measurements
A healthy dc bus is a must for a
properly operating motor drive. If
the bus voltage is not correct or
unstable it may be an indication
that the converter diodes or
capacitors may be starting to fail.
The dc bus voltage should be
approximately 1.414 times the
phase to phase input voltage.
For a 480 volt input, the dc bus
should be approximately 679
V dc. The DC Bus is typically
labeled as DC+, DC- or B+, B- on
the drive terminal strip.
To measure the dc bus voltage:
1. Select the 289’s dc voltage
function.
2. Connect the black probe to
either the DC- or B- terminal.
3. Connect the red probe to the
DC+ or B+ terminal.
The bus voltage should agree
with the example mentioned
above and be relatively stable.
You can also check the amount
of ac ripple on the bus by simply
switching the 289’s function
switch to the vac function.