Insulation resistance 19 spot or timed insulation resistance test 20 polarisation. This kit also includes test spikes electrodes for making temporary earth spikes. The way the connections are made depends on the type of test being undertaken and details are given in measuring techniques. Megger is also called as a megaohmmeter and is a device used for the testing of insulation resistance of a cable. Identifying motor defects through fault zone analysis. Similarly the range of ammeter and voltmeter during blocked rotor test, 10a, 250v. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. Unlike an ohmmeter, a megger can measure highvoltage resistance values, which are generally the kinds of values you will encounter with threephase motors. Motors are susceptible to the gradual failure of their insulation resistance. In this video you will find out how to test 3phase induction motor. The test voltage is the rated voltage of the cable the linetoline voltage.
Actually voltage or current unbalance will produce too much heat thus damaging the motors. Com 99 washington street melrose, ma 02176 phone 7816651400 toll free 18005178431 visit us at. Implementing a predictive maintenance program takes a. To perform an insulation spot test, apply the following procedure. Motors shall be bumped to verify proper direction of rotation.
During the testing procedure, the high dc voltage generated by pressing the test button will cause a small microamps current flow through the conductor and the insulation. Jul 17, 2017 release the push button on the megger or stop the cranking of the meter. How to test a 3 phase motor windings with an ohmmeter. This might result in unexpected motor failures when critical services from such motors are required affecting availability of plants. Motor heater sizes shall be checked for proper size. The idea is that the insulation resistance should increase over. Figure 2 typical megger test instrument hookup to measure insulation resistance. Test performed so performed to know the insulation resistance value is. Reverse side of card at right is used to record the test data. Perform this procedure a number of times as most dc motors use a carbon brush and copper commutator to conduct the electrical power to the armature. For good insulation, the resistance usually reads in the megohm range. Motors a 1,000 volt megger test shall be performed on 460 volt motors. The most common failure mode of a 3 phase ac motor is burnt winding or shorted winding leading to the damage of the motor. A guide to low resistance testing test equipment depot.
The test method is determined by the type of equipment being tested and the reason for test. To obtain short circuit current and its power factor angle, block rotor test is performed on the motor. This guide explains the power factor test procedure of these surge arresters. This unfortunately does not provide enough information to allow most electricians to feel totally confident in. Understanding insulation resistance testing pdf 0206 rev. Using a pi test to determine the condition of the motor can be misleading. Bethel electrical maintenance personnel have for years been limited to troubleshooting with no more than a fluke and a megger. However, lets talk now about three basic types of insulation resistance tests using megger tester.
Electrical test equipment power station to plug megger. Hi, ive been asked to find an ieee or equivalent test procedure for meggering from the tleads in an mcc cubicle to the motor in the field. Industries of today use threephase motors widely in highpower applications. How to use a megger to measure and test motor insulation. Section 7 of the ansineta standard for acceptance testing specifications for electrical power equipment and systems may be reproduced and used on a cut and paste basis for the particular type of equipment to be tested. Threephase dualvoltage motor insulation resistance testing threephase dualvoltage motors are used for most daytoday operations in todays industrial plants. Megger has offered a 10 kv insulation resistance tester since 2001. The motor under test must be powered down and disconnected from all equipment and wiring not included in the test. It is most commonly used in industrial installations with multiphase power supplies. Testing and diagnostics 14 trending of test data 17 megger baker mtr105 the tests 18. If a motor insulation test high potential insulation test must be performed, disconnect the motor from any speed control or drive to avoid damage to connected equipment. Insulation resistance testing is a nondestructive test procedure. Note that the megger can check for faults to the motor iron, but not short.
A guide to diagnostic insulation testing above 1 kv euro index. Dc motor analysis a leader in electric motor testing. The possibility exists that a fault in the power system will cause a high current to flow into the ground system while the test is in progress. Find here insulation testing and continuity, power protection, power transformer testing, power cable infrastructure, cable fault location, general electrical test. In using the megger, a bit of a learning curve is involved.
The correct settings, connection procedures, test durations and safety. What is megger test and how is it performed the device is being used since 1889, popularity raised during 1920s, since long back devise is same in its uses and purpose of testing, few real improvement appeared in recent years with its design and quality of tester. The correct settings, connection procedures, test durations and safety precautions must be implemented to avoid damaging the equipment or possible electrocutions. If you are testing a newer motor, one whose megger readings are in the gigaohms range, then the ratio between the 1 min and 10 min reading may end up being 1. Dielectric absorption test the dielectric absorption or timeresistance test is an extension of the insulation resistance test where instead of a spot test, the testing device is applied to the insulation for up to 10 minutes.
If any particular phase fails the continuity test, your motor is probably burnt. The test measurement data can be recorded on a test graph over time. Three phase motors, ac motors, insulation resistance. How to megger a motor also known as an insulation test. Work permit shall be prepared prior to start any activities. A spot test should be performed at regular intervals every six months, for example to track the changes in insulation integrity. Aug 01, 2019 in addition to these uses of this test, the working principle, operation procedure, types, and applications have also been discussed. High power test and diagnostics combination for medium voltage cables. Assuming by megger you mean insulation resistance tester then you are using the wrong scale, these devices read in the megohm scale not. The leads used for connecting megger testing with the circuit should be fault free and the two connecting leads should have electrical continuity. Visual inspection and electrical testing of the armature and fields give the maintenance personnel an understanding of the condition of the motor. How to test a threephase motor with a megger hunker. Threephase dualvoltage motor insulation resistance testing. To measure the resistance in a threephase motor, you will need a megohmmeter, otherwise known as a megger.
This may cause unexpected high voltages to appear at the current and voltage. A protocol involving voltage level, time duration, intervals between tests and connection methods must be composed, taking into account the type and size of the equipment, its value and role in the production process and other factors. Overhead crane inspector certification course online. Figure 3typical scale on the megger insulation tester. Ir value will be usually high several hundred megaohms for a dry insulation system. Megging a motor is a term used to test a 3 phase motor to check the resistance and condition of the motor windings using a megohmeter.
Standard for acceptance testing specifications for. Insulation resistance testing of low voltage cables in the field. Curve b shows same values corrected to 20c see page 22, giving a definite downward trend toward an unsafe condition. Using megger tester for these 3 types of insulation. Background the following is a summary of insulation resistance ir testing commonly referred to as megger testing of low voltage cables rated less than 5 kv, recognized by nexans. These motors run conveyor belts, pumps, fans, and many other applications. The procedure of insulation resistance test or megger test are given below. Due to heat, vibration, and limited space, the insulation on motor windings is the weak link. First, to protect yourself, be sure the motor rests on an insulated pad. Often it is required to test the winding of the 3 phase windings with the aid of a multimeter or ohmmeter to determine whether the motor is still good or burnt or shorted. Any voltage larger than this may stress the cable and cause premature failure. Megger testing procedures ieee electrical code issues. Testing the thyristors step by step before disconnecting the cables mark them.
The test measures the insulation resistance between the phases andor between phase and ground. Insulation resistance or ir test is carried out by maintenance engineers to ensure the healthiness of the overall insulation system of electrical equipment it reflects the presence or absence of harmful contamination, dirt, moisture, and gross degradation. Insulation resistance testing of low voltage cables in the. An instructional video on how to megger a motor and the proper use of a megohmmeter. The instrument is housed in a robust and tough case moulded in abs plastic. Each phase to phase must have a continuity if winding is ok. Jun 05, 2015 when it comes to checking out electric motors, there are special measuring instruments that may be used to detect and diagnose malfunctions. It is checked by touching the free ends of the leads together while the megger button is pressed on to check for zero.
How to meg a motor with a megohmeter checking motor condition. Rotate the end shaft approximately 30 degrees and test the motor again. All safety materials and equipment warning signs, barricades, fire extinguisher, etc. The generator can be handcranked or lineoperated to develop a high dc voltage which causes a small current through and over surfaces of the insulation being tested fig. For three phase motors, connection type is either star y or delta ac motor winding continuity test using a multimeter, check the continuity of motor winding from phase to phase u to v, v to w, w to u. The megger technical library provides access to a range of additional content and resources such as technical guides, application notes and more. Mar 28, 2018 in this video you will find out how to test 3phase induction motor. The test should also be performed after a motor is serviced. A 500 volt megger test shall be performed on 200 volt and 120 volt motors. Apr 09, 2017 a megger is used to verify the integrity of the insulation for safety reasons. As indicated previously, this direct measurement of. Ieee std 1122004, ieee standard test procedure for polyphase.
How to test three phase ac motors learning electrical. It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. The device is being used since 1889, popularity raised during 1920s, since long back devise is same in its uses and purpose of testing, few real improvement appeared in recent years with its design and quality of tester. Test to obtain more reliable values ranges of both wattmeter should be 10a, 250v for blocked rotor test. The term motor used in this checklist refers to all kinds of motors ge produced which are stated in section 4 in this document. There is an inherent safety problem in earth resistance testing that requires care and planning by the user of the test set. Test leads are not supplied with an instrument but form part of an earth testing field accessory kit which is available as an option. Using the megger to test a threephase motor is rather easy, though the safety hazards for this procedure are quite high.
The complete guide to electrical insulation testing. Timeresistance testing method this method is fairly independent of temperature and often. Figure 4typical record of insulation resistance of a mill motor. A viable solution is to megger test with highvoltage test equipment using 1,000 10,000. Identifying motor defects through fault zone analysis by noah p. Dc motor fault zone analysis is a vital part of any dc motor maintenance program. An operational test shall be performed on the motor controls. Additional notes about using a megger insulation tester 33. In addition to these uses of this test, the working principle, operation procedure, types, and applications have also been discussed. This is an insulation test of motor windings, commonly referred to as megging, to megger, or to meg a motor. Well learn how to identify windings, check windings resistance and insulation resistance. A catalogue, for quick reference, of the range of megger test instruments for the maintenance of electrical power systems. Ieee std 1122004 revision of ieee std 1121996 ieee standard test procedure for polyphase induction motors and generators sponsor electric.
How to test a 3phase motor is discussed in this article. The following sections of the ansineta standard for acceptance testing specifications for. The insulation resistance tester, generally known by its trade name megger, is capable of providing critical information regarding the condition of motor insulation. Isbn 07389785 ss95211 no part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher.
Ac motors types 10 star configuration 11 delta configuration 12 star vs delta configuration 12. Oct 19, 2015 how to troubleshoot 3 phase 240 or 480 volts any motor 3 leads 6 leads or 9 leads duration. The purpose of a surge lighting arrester is to limit the over voltages that may occur across transformers and other electrical apparatus due either to lightning or switching surges. The above variables should be controlled as much as possible to promote accurate insulation resistance measurement data. Jul 06, 2016 the test generally applies between 100 and 5,000 v or more. Test spikes and long test leads are necessary for all types of earth testing and the optional earth testing field. What is the procedure for testing insulation resistance in.
To accomplish this, a test procedure should be established and used consistently over time. Megger guide to electrical insulation testing pdf instrumart. A megger is used to verify the integrity of the insulation for safety reasons. Ieee std 1122004, ieee standard test procedure for. Connect the megger ground lead to the same ground plane the motor is connected to. Threephase power, introduced by inventor nikoa tesla, uses a polyphase system of alternating current to supply power to large motors and motor control. If you have any questions or are uncertain about any statement or procedure, or if you require additional. To be able to follow this instruction, you will need a megger. Power factor testing of surge lighting arresters megger.
Any help would be m megger testing procedures ieee electrical code issues engtips. From power station to plug, megger test equipment helps you maintain the electrical network, monitor its condition and maintain supply to your customers. Why is the test needed and which test method is it best to use. Disconnect the power cables from the main terminals 1l1, 3l2, and 5l3 and the motor cables from terminals 2t1, 4t2 and 6t3. Megger makes electrical test equipment to help you install, improve efficiency and extend the life of electrical assets and cable networks at high, medium and low voltage. In this method, you simply connect the megger instrument across the. With this test equipment, you can identify insulation leakage in motor coils and related wiring. This current usually at an applied voltage of 500 volts or more is measured by the ohmmeter, which has an indicating scale. Threephase dualvoltage motors are used for most daytoday operations in todays industrial plants.