Megger WM6 Manuale utente
M
WM6
Wee Megger Tester
User Guide
Guide de l’utilisateur
Gebrauchsanleitung
Guía del usuario
SAFETY WARNINGS
★
The circuit must be de-energized and isolated BEFORE connections are
made for any test.
★
Do not touch the circuit during an insulation test.
★
After insulation tests, capacitive circuits MUST be allowed to discharge
BEFORE disconnecting the test leads.
★
Test leads, including prods and crocodile clips, must be in good order;
clean and having no broken or cracked insulation.
★
Replacement fuses must be of the correct type and rating.
Refer also to page 8 for further explanations and other precautions.
The warnings and precautions must be read and understood before the
instrument is used. They must be observed during use.
2
NOTE
This instrument must only be used by suitably trained and competent persons.
CONTENTS
Safety Warnings 2
General Description 4
Applications 4
Specification 5
Accessories 7
Operation 8
Warning 8
Preliminary checks 8
Fuse replacement 8
Insulation testing 9
Continuity testing 9
Using the Insulation Tester 10
Preventive maintenance 10
Insulation Testing concepts 11
Mode d’Emploi 12
Betriebsanleitung 14
Instrucciones de Uso 16
Setting-up Procedure 18
Repair and Warranty 19
3
GENERAL DESCRIPTION APPLICATIONS
The WM6 MEGGER®Insulation and Continuity Tester
is a completely self contained instrument designed to
give rapid and accurate measurement of insulation
resistance and continuity resistance.
The WM6 uses a low voltage hand-cranked a.c.
brushless generator as the power supply. This
generator is easy to turn and is connected to a
rectifier and d.c. to d.c. converter to provide the test
voltage.
The WM6 uses a moving coil meter with taut band
suspension, white scales on a black scale plate and
an orange ‘dayglow’ pointer. An electronic circuit is
employed to produce a four decade calibrated scale
for insulation resistance measurement from 0 to
200 MΩ.
Two shrouded sockets are provided in the side of the
case for the test leads and a slider switch selects
either insulation or continuity tests (‘MΩ’ or ‘Ω’). The
case is robust, made of ABS plastic, and the
generator handle folds neatly against it when not in
use.
The WM6 is intended for the direct measurement of
insulation resistance and continuity of domestic and
industrial wiring, cables, transformers, motors,
generators, electrical machinery and appliances.
Because the WM6 is self-powered it is suitable for
use during installation and commissioning work as
well as for service and maintenance applications.
Note:— The cover of this instrument has been given
an antistatic treatment which should be
effective for many months. If in the course of
time the cover is found to retain electrostatic
charges, it should be re-treated with a
suitable antistatic solution.
4
SPECIFICATION
WM6
Ranges insulation 0–200 MΩand ∞
continuity 0–100 Ω
Terminal Voltage insulation range <600 V
on Open Circuit (d.c.) continuity range 800 mV approx.
Terminal Voltage at insulation range 500 V + 10% –5%
1 MΩLoad (d.c.)
Terminal Current insulation range 1,3 mA approx.
on Short Circuit continuity range 55 mA approx.
Voltage Stability insulation range <±1%
160 r.p.m. to 240 r.p.m.
Ripple Content at 160 r.p.m. insulation range 500 mV pk-pk approx.
on Open Circuit
Accuracy 1,5 mm (0,060 in) from any marked position on the
scale when measured against standard resistors.
Temperature operating –10 °C to +50 °C
storage –20 °C to +70 °C
Flash Test 2,3 kV a.c. r.m.s.
Voltage Source (d.c.) Brushless a.c. hand-cranked generator with
rectifier and d.c. to d.c. converter.
5
SPECIFICATION
Fuse 1 A 20 x 5 mm ceramic
Dimensions 131 x 98 x 61 mm (51/8x 37/8x 23/8in)
Weight 650 g (1 lb 7 oz)
Terminal Voltage Characteristics
6
WM6
Terminal voltage (volts d.c.)
Resistance under test (MΩ)
SPECIFICATION ACCESSORIES
Illustrations of Typical Scales (full size)
WM6
SUPPLIED WITH THE INSTRUMENT
Test lead set including shrouded crocodile clips
User Guide Part No. 6171-685
Test Record Card (5 supplied) Part No. 6172-111
AVAILABLE AS AN OPTIONAL EXTRA
A ‘test-and-carry’ case with a special
compartment for test leads Part No. 6420-088
Test Lead set red/black Part No. 6220-437
Test Record Card (Pack of Twenty)
Part No. 6111-216
7
OPERATION
WARNING
1. The circuit under test must be de-energized and
isolated before insulation or continuity tests are
made.
2. When capacitive circuits have been tested allow a
suitable time to elapse before disconnecting the
test leads, for the circuit to discharge.
3. Instruments used in dusty environments should be
stripped and cleaned periodically.
4. Do not leave the instrument exposed to direct heat
from the sun for long periods.
5. The instrument circuit contains a static sensitive
device. If the instrument casing is opened for any
reason (this will automatically invalidate any
warranty covering the instrument), care must be
exercised in handling the printed circuit board.
This should be done in accordance with DEF
STAN 59-98 and BS 5783 specifications for
handling electrostatic sensitive devices.
Printed circuit boards containing such devices are
identified either by a yellow warning label or by a
yellow legend and a large yellow dot on the p.c.b.
(Initially the dot may not be included.)
PRELIMINARY CHECKS
Inspect the test leads to see that they have good
unbroken insulation. Connect the red and black leads,
terminated with the clips, to the red (+) and black (–)
terminal sockets respectively in the side of the
instrument case. Leave the leads coiled or twisted
together, but ensure that their clips are not touching
anything. Set the slider switch to the ‘MΩ’ position.
Turn the generator handle at approximately 160 r.p.m.
and observe the meter pointer, it should rest over the
‘∞’ (infinity) position on the scale. If it does not the test
leads may be faulty and should be inspected more
closely for damage. Replace them if necessary.
Connect the test lead clips together and turn the
generator handle again, the meter should read zero.
If it indicates infinity or a high resistance value the
leads may be open circuit and should be inspected
further, replace if necessary. Shorting the leads
together and obtaining a zero reading also proves that
the instrument is working.
To check that the fuse in the continuity circuit is intact,
leave the test leads connected together and set the
slider switch to the ‘Ω’ position. Turn the generator
handle again, the reading obtained should be zero (or
very nearly so). If the reading is beyond full scale on
the ‘Ω’ range the fuse has ruptured and should be
replaced.
8
FUSE REPLACEMENT
The fuse is held in a screw-type holder. To change a
fuse, use a screwdriver to release the centre part of
the holder containing the fuse. Replace with a 1 A
20 x 5 mm ceramic fuse part no. 25413-286. An
alternative fuse should not be used as the fuse
resistance will affect the lower continuity readings.
INSULATION TESTING
After connecting the test leads to the instrument and
making the preliminary checks as detailed above, set
the slider switch to ‘MΩ’. With the circuit to be tested
isolated, connect the test leads as follows:—
(a) for insulation tests to earth —
connect the red lead to earth or frame of the
equipment, and the black lead to that part of the
circuit to be tested.
(b) for insulation tests between wires —
connect a lead to the core of each of the wires.
Turn the generator handle at between 160 r.p.m. and
240 r.p.m. The meter pointer will indicate the value of
insulation resistance on the ‘MΩ’ scale. (If a capacitive
circuit is tested the pointer will initially deflect towards
zero and then gradually rise to its final steady value as
the capacitance is charged up to the output voltage of
the tester.)
If several successive readings of ‘∞’ are obtained,
connect the two further ends of the test leads together
and turn the generator handle. A zero reading should
result which double checks that the leads are not
disconnected or broken and therefore the insulation
resistance readings are correct.
Capacitive circuits automatically discharge through
the tester when the generator handle stops rotating.
The meter pointer will deflect beyond the ‘∞’ position
on the scale and then return to its normal rest position
at ‘∞’ when the circuit has discharged. Wait a few
moments for this to happen before disconnecting the
test leads. The discharge time (to 0 V) is approx. 8
seconds per microfarad.
CONTINUITY TESTING
With the test leads connected to the instrument, and
having checked them and the fuse as described
above, set the slider switch to the ‘Ω’ position. With the
circuit under test isolated, connect the test leads
across the appropriate points and turn the generator
handle at between 160 r.p.m. and 240 r.p.m. The
resistance will be indicated on the ‘Ω’ scale. This
resistance includes that of the test leads which should
be measured separately, (by performing a test with
the clips joined together), and the result deducted
from the total.
9
Preventive Maintenance
The proverb ‘A stitch in time saves nine’ inspired the
title of an Megger Limited booklet on insulation
testing, as it neatly sums up the benefits of
preventative maintenance. The savings come in
financial terms from costly repairs, lost production, lost
profits and in human terms, from lives saved in the
event of dangerous electrical faults.
Regular insulation testing of electrical equipment can
help to detect deteriorating insulation. The effects
which cause insulation to deteriorate include
mechanical damage, vibration, excessive heat or cold,
dirt, oil, moisture and localized voltage stresses - all of
which can arise on most industrial or utility equipment.
Insulation tests are sometimes used in isolation as
absolute measures of the quality of the insulation. This
is most appropriate when equipment is being installed
and checked for compliance with a specified ‘Pass’
level. For operational equipment the key factors are
trends in the insulation readings.
It is therefore important that records of insulation
readings are kept, relating to each piece of equipment
or ‘Asset’ in your testing regime. Megger Limited
supplies test record cards to assist with such record
keeping. There are also a number of influences on the
insulation readings - temperature, humidity and
surface leakage for example and a range of test
techniques have been developed to help with the
interpretation of your insulation tests.
10 Test Record Example
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