What is the procedure for testing insulation resistance in. Have anyone hear of a hi megger testing residential circuits as part of their home inspection. However, lets talk now about three basic types of insulation resistance tests using megger tester. Megger has been at the forefront of innovation in the electrical power test and measurement field for over 100 years. A 1,000 volt dc megger test shall be performed on buses, motor starters, circuit breakers, and disconnect switches. The test measures the insulation resistance between the phases andor between phase and ground.
Jul 06, 2016 testing electric motors doesnt have to be a mystery. In the usa, the industrial power supply voltage is 480 volt 3 phase i think, and motors for this supply might be better tested at say 750 volt. A continuity check shall be performed on motor control circuits and control panel internal wiring. Rotate the end shaft approximately 30 degrees and test the motor again. Capacitors shall be inspected for proper fuses before testing. Insulation resistance testing guide chauvin arnoux. But before starting turn off all power sources to machine then disconnect the 3 phase motor lines. How does one interpret the results of the megger test if the result shows that the resistance is under 1 on the meter, after the first 60 seconds, it likely means that the cable has an issue and needs to be removed. Electrical acceptance tests architecture engineering and. It is checked by touching the free ends of the leads together while the megger button is pressed on to check for zero. The correct settings, connection procedures, test durations and safety precautions must be implemented to avoid damaging the equipment or possible electrocutions. They interact with each other and cause a gradual spiral of decline in insulation quality. Motor testing with ohm meter and megohm meter servo motor. Most electrical associations recommend this procedure.
In this test we use megger in megger generally two components are present dc generator and ohm meter dc generator generate high voltage such as. Using the megger to test a threephase motor is rather easy, though the safety hazards for this procedure are quite high. How does one interpret the results of the megger test. If shaft rotation is free and smooth, bearing is possibly in good condition, otherwise consider replacing. Delivered in onsite case with 1 operating manual, 2 elbowedstraight pvc. As electrical insulation breaks down, there are many hazards that can occur. The complete guide to electrical insulation testing. For good insulation, the resistance usually reads in the megohm range however, lets talk now about three basic types of insulation resistance tests using megger tester. Ieee std 1122004 revision of ieee std 1121996 ieee standard test procedure for polyphase induction motors and generators sponsor electric. It is most commonly used in industrial installations with multiphase power supplies. How to megger a motor also known as an insulation test. A guide to low resistance testing test equipment depot. Baker instruments is a leading provider of test equipment for the electrical condition monitoring of motors, generators and coils. This is an insulation test of motor windings, commonly referred to as megging, to megger, or to meg a motor.
Curve b shows same values corrected to 20c see page 22, giving a definite downward trend toward an unsafe condition. The motor and phase rotation tester permits the electrical contractor or industrial maintenance electrician to permanently connect and tape the terminals of the motor being installed, without having to first energize the motor by a temporary hookup from a power source, if. I believe you are right about the guard being at the same potential as the negative. 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. Electricians motor and generator testing equipment megger. 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. There are five basic causes for insulation degradation. Insulation resistance testing of low voltage cables in the field. The following sections of the ansineta standard for acceptance testing specifications for. 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.
Be sure to follow good safety measures to prevent electrical shock. Insulation resistance testing is a nondestructive test procedure. A troubleshooting procedure consists of systematic testing designed to identify and correct a problem. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms.
It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. Electrical test equipment power station to plug megger. Unlike an ohmmeter, a megger can measure highvoltage resistance values, which are generally the kinds of values you will encounter with threephase motors. Whether you are testing in a motor repair shop, in an industrial plant, on a ship or up a wind turbine, baker instruments motor test equipment allows you to fully understand the condition of the motor, the power supply and the load. Due to heat, vibration, and limited space, the insulation on motor windings is the weak link.
The procedure of insulation resistance test or megger test are given below. Inspection and test procedures for rotating machinery. Electrical stress insulation is designed for a particular application. Figure 4typical record of insulation resistance of a mill motor. Regular insulation resistance testing is one of the most cost effective, nondestructive methods of identifying ageing in electrical equipment. Note that the megger can check for faults to the motor iron, but not short.
From power station to plug, megger test equipment helps you maintain the electrical network, monitor its condition and maintain supply to your customers. Reverse side of card at right is used to record the test data. 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. Synchronous motors and generators procedures index 1. 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. How to test three phase ac motors learning electrical.
So when a motor fails to operate it may not be obvious what the problem is. The megger insulation tester is an instrument used for measuring high resistances of the order of mega ohms and for testing the insulation resistance. 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. Connect the megger ground lead to the same ground plane the motor is connected to. Motors tested to neta ats 2007 with 34,500 v or above on their. Electric motors insulation resistance testing is performed when troubleshooting electric motors and. Three phase motors, ac motors, insulation resistance. The motor under test must be powered down and disconnected from all equipment and wiring not included in the test. See how to measure insulation resistance of electric motor running amps test with the motor running, check the full load amps fla with a suitable meter or preferably a clamp on meter and compare with the name plate fla.
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. Insulation testing technical guides megger insulation. Megger test equipment products on sale at tequipment. By testguy in forum news and announcements replies. This test may be combined with the cable megger test by power testing the devices and terminated cables together. A 1,000 volt megger test shall be performed on 460 volt motors. The megger insulation tester is essentially a highrange resistance meter ohmmeter with a builtin directcurrent generator.
A guide to diagnostic insulation testing above 1 kv. 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. Weve assembled helpful technical guides on insulation testing from leading manufacturers in the field. But before starting turn off all power sources to machine then disconnect the 3 phase motor lines only from the drive. Standard for acceptance testing specifications for. Insulation resistance testing of low voltage cables in the.
Delivered with a handsfree bag containing a set of 2 leads 1. Connect the megger hot lead to a motor winding lead. The test method is determined by the type of equipment being tested and the reason for test ing. They are known for creating the first original electrical insulation tester and continue to supply high quality equipment today.
Using megger tester for these 3 types of insulation. Ieee std 1122004, ieee standard test procedure for. How to troubleshoot 3 phase 240 or 480 volts any motor 3 leads 6 leads or 9 leads duration. Figure 2 typical megger test instrument hookup to measure insulation resistance. Polarisation index is the ratio of megger value taken for 10 minutes to the megger value taken for 1 minute.
How to use a megger to measure and test motor insulation. Threephase dualvoltage motor insulation resistance testing. Any help would be m megger testing procedures ieee electrical code issues engtips. Below are some basic principles for testing servo motor circuits with meter or megohm meter. Threephase dualvoltage motor insulation resistance testing threephase dualvoltage motors are used for most daytoday operations in todays industrial plants. Megger testing of residential circuits inspectionnews. Megger has published a book titled getting down to earth, a practical guide to earth resistance testing. Electric motors have had a reputation for being a mix of science and magic. Megger working principle megger working principle is based on the working principle of moving coil instruments, which states that when a current carrying conductor is placed in a magnetic field. A megger is used to verify the integrity of the insulation for safety reasons. Pd testing on switchgear aisgisgil water leak detection and monitoring. The megger insulation tester is an instrument used for measuring high resistances of the order of mega ohms and for testing the insulation resistance megger working principle.
My view about testing small motor windings is that a 500 volt dc megger is what is required. Motors are susceptible to the gradual failure of their insulation resistance. Knowledge of the basics together with powerful new test equipment vastly simplifies the job. Apr 09, 2017 a megger is used to verify the integrity of the insulation for safety reasons. The megger technical library provides access to a range of additional content and resources such as technical guides, application notes and more. If the motor is not put into operation immediately upon arrival, it is important to protect it against external. Jul 17, 2017 release the push button on the megger or stop the cranking of the meter. For instance, when testing electrical cabling or switchgear. This document will focus only on the tests that are of importance for field installers which are described as installation and maintenance tests. It can give an accurate reading of the measure of resistance and continuity available in a highvoltage circuit and electrical motor. The insulation resistance tester, generally known by its trade name megger, is capable of providing critical information regarding the condition of motor insulation. I have not personally ever used a megger but from what i understand that type of test would be very time consuming or am i missing something.
Troubleshooting with insulation resistance test instruments. 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. Neta test forms tests performed by testing organization. A 1,000 vdc megger test olt shall be performed on 460 volt capacitors, and a. This is important, because the highvoltage current in threephase. Oct 19, 2015 how to troubleshoot 3 phase 240 or 480 volts any motor 3 leads 6 leads or 9 leads duration. These motors run conveyor belts, pumps, fans, and many other applications. 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. This current usually at an applied voltage of 500 volts or more is measured by the ohmmeter, which has an indicating scale. Megger working principle is based on the working principle of moving coil instruments, which states that when a current carrying conductor is placed in a magnetic field, a mechanical force is experienced by it. Megger has offered a 10 kv insulation resistance tester since 2001. Ieee std 1122004, ieee standard test procedure for polyphase. How to test a threephase motor with a megger hunker. Figure 3typical scale on the megger insulation tester.
To measure the resistance in a threephase motor, you will need a megohmmeter, otherwise known as a megger. When it comes to checking out electric motors, there are special measuring instruments that may be used to detect and diagnose malfunctions. A guide to diagnostic insulation testing above 1 kv 5 what causes insulation to degrade. Standard for acceptance testing specifications for electrical. Megger testing procedures ieee electrical code issues. The leads used for connecting megger testing with the circuit should be fault free and the two connecting leads should have electrical continuity. The motor and phase rotation tester permits the electrical contractor or industrial maintenance electrician to permanently connect and tape the terminals of the motor being installed, without having to first energize the motor by a temporary hookup from a power source, if available, to determine motor rotation. Jan 31, 2019 again when we take the megger value of the insulator for 10 minutes, the megger result shows the ir value, free from effects of both capacitive component and polarisation component of the current. An instructional video on how to megger a motor and the proper use of a megohmmeter. Megger makes electrical test equipment to help you install, improve efficiency and extend the life of assets and cable networks at high, medium and low voltage.
Meggers motor and generator testers ensure the correct phase connection in one of our easytouse testers. If you reference a power factor test set this would make sense. Com 99 washington street melrose, ma 02176 phone 7816651400 toll free 18005178431 visit us at. The insulation resistance tester, generally known by its trade name megger, is capable of providing critical information regarding the. This procedure will show you how to test for shorts in windings, cables or opens. Diagnostic dc testing is probably the easiest and most convenient method of achieving this due to the small size and weight of the equipment. Minimum test value of motor insulation resistance is 1 meg ohm 1 m. Adequate space shall be allowed for the safe operation and maintenance of. Megger megohmmeter insulation resistance testers megohmmeters, or insulation resistance ir testers, are used to measure the resistance, integrity and safety of electrical wiring insulation.
Megger guide to electrical insulation testing pdf instrumart. The surface of the conductor is free of hydrocarbons and other foreign matter that can become conductive in humid. If shaft rotation is free and smooth, bearing is possibly in good condition, otherwise consider replacing, repair or carry out further diagnosis. For good insulation, the resistance usually reads in the megohm range. In using the megger, a bit of a learning curve is involved. Aug 05, 2017 in this we check induction motor by megohmeter. They can be quite different for one motor or machine tested three days in a row. Megger has combined all of the functions frequently required for testing electric motors in a unique and innovative. Pdf in part 1 have been presented some tests as insulation resistance megger and pi test. If the result shows that the resistance is under 1 on the meter, after the first 60 seconds, it likely means that the cable has an issue and needs to be removed. All of the new megger earth testers can perform this test and unlike some instruments, no external linking on the instrument is required. Again when we take the megger value of the insulator for 10 minutes, the megger result shows the ir value, free from effects of both capacitive component and polarisation component of the current.
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