Megger MOM690 User manual

Art No. ZP-BB05E Doc. BB0220IE V06a 2019
WWW.MEGGER.COM
User’s Manual
MOM690
Micro-ohmmeter

Contents
1 Introduction
___________________________________ 4
2 Safety
___________________________________ 6
2.1 Symbols on the instrument ................................. 6
2.2 Safety instructions............................................... 6
3 Control panel
___________________________________ 8
3.1 Panel description................................................. 8
3.2 Display................................................................ 9
Menu options ...................................................... 9
Program version................................................... 9
4 Operating instructions
__________________________________ 10
4.1 Connection setup ............................................. 10
4.2 Operating ......................................................... 11
Safety functions................................................. 11
Measuring in AUTO mode ................................. 11
Measuring in MAN mode .................................. 11
Demagnetizing current transformer cores .......... 11
Calibration......................................................... 11
4.3 Application examples........................................ 12
Measuring resistance in a breaker ...................... 12
Measuring resistance at bus-bar joints................ 12
4.4 Software........................................................... 13
4.5 Troubleshooting................................................ 13
5 Specifications
__________________________________ 14
Specifications MOM690.......................................... 14
Cable sets – load currents ....................................... 15

MOM690
Micro-ohmmeter
NOTICE OF COPYRIGHT & PROPRIETARY RIGHTS
© 2010-2017, Megger Sweden AB. All rights reserved.
The contents of this manual are the property of Megger Sweden AB. No part of this work may be reproduced or transmitted in any form or
by any means, except as permitted in written license agreement with Megger Sweden AB. Megger Sweden AB has made every reasonable
attempt to ensure the completeness and accuracy of this document. However, the information contained in this manual is subject to change
without notice, and does not represent a commitment on the part of Megger Sweden AB. Any attached hardware schematics and technical
descriptions, or software listings that disclose source code, are for informational purposes only. Reproduction in whole or in part to create
working hardware or software for other than Megger Sweden AB products is strictly prohibited, except as permitted by written license
agreement with Megger Sweden AB.
TRADEMARK NOTICES
Megger® and Programma® are trademarks registered in the U.S. and other countries. All other brand and product names mentioned in this
document are trademarks or registered trademarks of their respective companies.
Megger Sweden AB is certified according to ISO 9001 and 14001.
User’s Manual
Postal address:
Megger Sweden AB
Box 724
SE-182 17 DANDERYD
SWEDEN
T [phone]
F [phone]
[e-mail]
www.megger.com
Visiting address:
Megger Sweden AB
Rinkebyvägen 19
SE-182 36 DANDERYD
SWEDEN
BB0220IE ZP-BB05E MOM690 3

1Introduction
The MOM690 is designed to measure the resistances
of breaker contacts, bus-bar joints, contact elements
in bus-bars and other high-current links.
When contact resistance rises because of oxidation,
loosened or improperly tightened threaded joints,
temperatures rise abnormally at the points of contact.
This abnormal heating reduces conductivity thereby
accelerating the rise in temperature — and this often
leads to serious trouble.
The MOM690 can be used to detect such problems
early so that they can be remedied long before trouble
starts. Checking contact resistance at regular intervals
provides a clear indication of the state of your system.
During measurement, the instrument generates a high
current. This current must not cause excessive heating
inside the instrument. To prevent this, both a thermal
fuse and a miniature circuit breaker that serves as a
line fuse are provided. The instrument is equipped
with an induction protector. For protection against ex-
ternal overvoltages, both the current output and the
sensing input are decoupled to ground. A full-wave
rectified current, i.e. a pulsating DC current, is used
for measurement.
4MOM690 ZP-BB05E BB0220IE
1 INTRODUCTION

BB0220IE ZP-BB05E MOM690 5
2 SAFETY

2
Safety
2.1 Symbols on the
instrument
Caution, refer to accompanying docu-
ments.
Protective conductor terminal.
WEEE, Waste Electrical and Electronic
Equipment. Please utilize your local
WEEE collection facilities in the dispo-
sition of this product and otherwise
observe all applicable requirements.
The unit can also be returned to
Megger at any time at no charge for
the disposal.
Information duty regarding
substances on REACH article 33,
SVHC-list
This product contains a coin cell battery which con-
tains 1,2- dimethoxyethane (CAS 110-71-4) above
0.1% by weight.
2.2 Safety instructions
Important!
Read the manual and comply with the following
instructions before using the micro-ohmmeter.
Always comply with local safety regulations.
Warning
Before measuring resistances in circuit breakers or
disconnecting switches (isolators), always check
to see that the object being tested is closed and
grounded on one side.
If there is a current transformer in the current circuit,
the protective relay equipment that is connected
to it must be blocked to prevent actuation. After
completing your measurements, you can follow
the normal procedures that are used to demagnet-
ize current transformer cores after DC has passed
through their current transformer.
Never open a circuit breaker while a MOM690 is
connected to it.
The outputs DC+ and AC must not be loaded at the
same time.
Connection points for current cables can become
hot during current generation.
Current continues to flow for a while after the
MOM690 is turned off. How long it continues
depends on the ratio of the components in the L/R
circuit.
Important
Always connect protective earth (ground)
Always use safety connecting leads.
Always turn the equipment off before connecting.
High voltage/current on input/output terminals.
Never leave the instrument unattended while it is
turned on and in the highcurrent mode.
Unplug the instrument from the mains supply when
it is left unattended or not in use.
6MOM690 ZP-BB05E BB0220IE
2 SAFETY

Do not attempt to service the instrument yourself.
Opening or removing covers may expose you to
dangerous voltage. If you attempt to service the
instrument yourself the warranty is no longer valid.
Do not use any accessories that are not intended for
use together with the instrument.
Disconnect the instrument from the mains before
cleaning. Use a damp cloth for cleaning. Do not use
liquid cleaners or aerosol cleaners.
Use only approved mains detachable cable set with
the instrument. Main supply cables shall be rated for
the maximum current for the equipment and the ca-
ble shall meet the requirements of IEC 60227 or IEC
60245. Mains supply cables certified or approved by
a recognized testing authority are regarded as meet-
ing this requirement.
Refer all servicing to Megger authorized personnel.
If you need to return the instrument, please use ei-
ther the original crate or one of equivalent strength.
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2 SAFETY

3Control panel
3.1 Panel description
1. Grounding terminal
2. Connection for mains voltage
3. Miniature circuit breaker for mains
4. Switch for mains voltage
5. Variable transformer
6. AC current output (–)
7. AC/DC current output
8. DC current output (+)
9. Sensing terminal
10. Display
11. Scrolling key for the display
12. Function selector
13. Interrupts current and toggles the display
between resistance and voltage
14. Serial interface for PC (RS 232)
⓭
4
3
2
5
6
7
❿
9
⓫
8
⓬
1
⓮
8MOM690 ZP-BB05E BB0220IE
3 CONTROL PANEL

3.2 Display
Indicates whether the cur-
rent is above (>) or below
(<) a preselected value.
Value of the generated
current.
Information about
current generation or
memory location.
Shows the measured resistance
or voltage value. Toggle by
pressing the <Ω>-key.
Selected function. Scroll
using the <FUNC>-key.
Selected test current for
"Auto"/"DC Off"
Scroll using the <▲>-key.
>A 123A DC On
100A AUTO 100µΩ
Menu options
You can make different settings with the keys beneath
the display.
Select language
>A 118A DC On
100A AUTO 63µΩ
1] Press the <FUNC>-key to enter the "AUTO"
or "MAN"mode.
2] While holding down the <▲>-key, press the
<FUNC>-key.
Select language
ENGLISH OK
3] Use the <▲>-key to scroll to the desired lan-
guage.
4] Finish by pressing the <W>-key.
Save test results
Record Mem1-30
On REC Save
The memory function is turned on or off using the
<▲>-key. When you take measurements in the
"MAN" or "AUTO" mode, the values measured are
stored in the memory.
>A 123A Rec>1
100A AUTO 67µΩ
Memory locations are filled successively until all 30 are
full, whereupon the next measured value replaces the
oldest of those already in the memory.
100A Mem-8
View PLAY 57µΩ
To view the values stored in memory, scroll to "PLAY"
using the <FUNC>-key. Then step forward in the
memory by pressing the <▲>-key (hold the key down
to step faster). Press the <Ω>-key to view the voltage
value, and press it a second time to view the resist-
ance value.
Note Values stored in memory vanish when you
turn of the MOM690.
Save values permanently
1] To save the values permanently, you scroll to
the "REC" position using the <FUNC>-key.
2] Then press the <Ω>-key, whereupon the val-
ues will be saved.
Saving Mem1-30..
Reset all values in the memory
1] Step to "AUTO" or "MAN" using the
<FUNC>-key.
2] While holding down the <▲>-key, press the
<Ω>-key.
3] Press the <FUNC> key to reply “Yes”.
Program version
To view the program version, first press the <FUNC>-
key and then, while holding it down, press the <Ω>-
key.
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3 CONTROL PANEL

4Operating instructions
4.1 Connection setup
Important
Read the manual and comply with the
Safety instructions, see page 6, before
using the micromhmeter.
Always comply with local safety regula-
tions.
Warning
If there is a current transformer in the
current circuit, the protective relay equip-
ment that is connected to it must be
blocked to prevent actuation.
If you are measuring resistance in a circuit
breaker or disconnecting switch (isolator),
make sure that it is closed before starting.
High current must only flow throughout a
short interval. Never leave the instrument
unattended while it is turned on and in
the high-current mode.
1] Make certain the mains are de-energized on
both sides of the breaker. Ground the break-
er on one side and make certain it is closed.
2] Keep the MOM690 disconnected from the
mains while making connections.
3] Ground the MOM690.
4] Connect one current cable between one
side of the object being tested and the DC+
terminal on the MOM690. Connect the other
current cable between the other side of the
object being tested and the COM- terminal
on the MOM690.
5] Connect the two sensing cables (using the
same polarities as those used for the current
cables) on two sides of the test object and as
close to the test object as possible.
Important:
The sensing cables must be connected inside
the current cables. Otherwise the test data
may be incorrect. See Fig.1.
6] Connect the MOM690 to the mains and
switch it on.
Note Since power consumption is high, the instru-
ment requires a 16 A fuse.
7] Select "AUTO" or "MAN" with the <FUNC>-
key.
Test object
Fig. 1
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4 OPERATING INSTRUCTIONS