Megger WM6 Manuale utente

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.

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

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.

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.

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

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

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.

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.

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

Indice

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