This current usually at an applied voltage of 500 volts or more is measured by the ohmmeter, which has. The procedure of insulation resistance test or megger test are given below. Jan 16, 2016 this is an insulation test commonly referred to as megging, to megger, or to meg a motor. Make sure the current connections are clean and tight. Only megger approved test leads must be used with this product. Coils ii, iii, and iv are permanently connected and cannot be separated. First we will disconnect all the line and neutral terminals of the transformer. Standard for acceptance testing specifications for. Although every effort is made to ensure the accuracy of the information contained within this document it is not warranted or represented by megger ltd. How to use a megger to measure and test motor insulation. Readings should be within the specifications provided by the manufacturer. How to test a threephase motor with a megger hunker.
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. Megger is also called as a megaohmmeter and is a device used for the testing of insulation resistance of a cable. Curve b shows same values corrected to 20c see page 22, giving a definite downward trend toward an unsafe condition. 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. Aug 01, 2019 in addition to these uses of this test, the working principle, operation procedure, types, and applications have also been discussed. Push the test button of the megger to generate the voltage. This is important, because the highvoltage current in threephase systems is far more lethal than a mere lowvoltage shock received in residential setting. You can then perform the following insulation resistance tests. For a three phase motor, insulation resistance is usually measured between each motor winding or phase and between each motor phase and motor frame earth using an insulation tester or megger. In using the megger, a bit of a learning curve is involved. Test current adjustment test current indicated on the ammeter should. Megger leads to be connected to lv and hv bushing studs to measure insulation resistance ir value in between the lv and hv windings.
Even though a fault in your motor can be found out with the help of a multimeter, still becoming doubly sure really helps. It is practically impossible to determine rules for the actual minimum insulation resistance value of a motor because resistance varies according to method of construction, condition of insulation material used, rated voltage, size and type. The megger technical library provides access to a range of additional content and resources such as technical guides, application notes and more. Figure 4typical record of insulation resistance of a mill motor. Also know as power factor and dissipation factor testing, these state of the art instruments give the user a wide range of results for qualitative cable assessments such as degradation and lifetime estimations on mv and hv systems. How to megger a motor also known as an insulation test. Select a voltage to apply to the motor using an output from the megger that is higher that the.
Connect the megger ground lead to the same ground plane the motor is connected to. Jul 17, 2017 release the push button on the megger or stop the cranking of the meter. Understanding insulation resistance testing pdf 0206 rev. Reverse side of card at right is used to record the test data. 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.
From power station to plug, megger test equipment helps you maintain the electrical network, monitor its condition and maintain supply to your customers. Initial and date the results of the following instructions and tests on attachments to this procedure. This is an insulation test of motor windings, commonly referred to as megging, to megger, or to meg a motor. The leads used for connecting megger testing with the circuit should be fault free and the two connecting leads should have electrical continuity. To properly test this type of motor, remove the wirenuts joining leads 4 and 7, 5 and 8, and 6 and 9. When the test terminals are open, the resistance to be measured is infinite. In an industrial facility, the recommended procedure is to perform periodic tests and record. Tan delta diagnostic high voltage test equipment megger. We are testing the motors insulation, more specifically between the motor windings and the motor casing. Ieee std 1122004 revision of ieee std 1121996 ieee standard test procedure for polyphase induction motors and generators sponsor electric. Section g recommended test leads megger test leads recommended for use with the 100 ampere range are as follows. This is an insulation test commonly referred to as megging, to megger, or to meg a motor. Safety, hazard and warning symbols on the instrument.
Using the megger to test a threephase motor is rather easy, though the safety hazards for this procedure are quite high. To test a motor, use a megger megohm meter to test the insulation of the internal motor windings. How to meg a motor with a megohmeter checking motor condition. 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. The working of megger insulation tester can be fully understood from the following steps. Meggers complete guide to electrical insulation testing pdf. If a fraction of current flows, it can be measured by these highly sensitive meters. Additional notes about using a megger insulation tester 33. Here we are showing you one verified brand new motor vs one that has been taken out of service. The correct settings, connection procedures, test durations and safety precautions must be implemented to avoid damaging the equipment or possible electrocutions. The complete guide to electrical insulation testing.
Mar 28, 2018 in this video you will find out how to test 3phase induction motor. Ieee std 432000 recommends a procedure for measuring insulation resistance of armature and field windings. Aug 16, 2014 the procedure of the insulation resistance test are given below first, disconnect all the line and neutral terminals of the transformer. Megger insulation tester calibration procedure megger insulation tester is measuring resistance by generating a voltage. High power test and diagnostics combination for medium voltage cables. It is checked by touching the free ends of the leads together while the megger button is pressed on to check for zero. Mar 26, 2017 push the test button of the megger to generate the voltage. You can test your motor insulation with the help of a megger. Megger and bridge test of motor cr4 discussion thread. Polarisation index is the ratio of insulation resistance at 1 minute to 10 minutes. 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. Threephase dualvoltage motor insulation resistance testing. If a motor has to have heat applied to get the megger reading up, then it will need a rewind eventually as the insulation is either tracking to ground or absorbing moisture.
Apr 09, 2017 a megger is used to verify the integrity of the insulation for safety reasons. Also know as power factor and dissipation factor testing, these state of the art instruments give the user a wide range of results for qualitative cable assessments such as degradation and lifetime estimations on mv and hv. On a good motor, a megger reading between phases will show a short. A guide to low resistance testing test equipment depot. Megger has offered a 10 kv insulation resistance tester since 2001. All safety materials and equipment warning signs, barricades, fire extinguisher, etc. Megger leads are connected to lv and hv bushing studs to measure insulation resistance ir. Connections and turnon connect the test sample to the terminals as shown in figure. Test performed so performed to know the insulation resistance value is. The motor under test must be powered down and disconnected from all equipment and wiring not included in the test. To test a cable with a megger, you connect one probe to the outside of the cable and, with the power turned off, you touch the probe to the conducting wire at the point of connection. Well learn how to identify windings, check windings resistance and insulation resistance. Figure 3typical scale on the megger insulation tester. Connect the megger hot lead to a motor winding lead.
To accomplish this, a test procedure should be established and used consistently over time. Another test we might do is called a polarization index test. In addition to these uses of this test, the working principle, operation procedure, types, and applications have also been discussed. Megger insulation tester calibration procedure calibration.
Be sure to follow good safety measures to prevent electrical shock. Some unknown facts was presented at the 2020 neta powertest conference in chicago, il. Figure 2 typical megger test instrument hookup to measure insulation resistance. The procedure of the insulation resistance test are given below first, disconnect all the line and neutral terminals of the transformer. Com 99 washington street melrose, ma 02176 phone 7816651400 toll free 18005178431 visit us at.
Megger testing procedures ieee electrical code issues. If the motor is kept in a place with high humidity, a periodical inspection is necessary. This article takes an indepth look at the transformer turns ratio test, some of the challenges associated with interpreting test results, and unknown facts related to test variables. Note that the megger can check for faults to the motor iron, but not short. Rotate the end shaft approximately 30 degrees and test the motor again. How to test three phase ac motors learning electrical.
Jul 06, 2016 the test generally applies between 100 and 5,000 v or more. Three phase motors, ac motors, insulation resistance. Megger leads are connected to lv and hv bushing studs to measure insulation resistance ir value in between the lv and hv windings. All test leads, probes and crocodile clips must be in good order, clean and with no broken or cracked insulation. A megger is used to verify the integrity of the insulation for safety reasons. 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. Section d operating procedure follow the safety precautions of section b measurements on 600o 100ampere dlro range 1. Note that the wyeconnected 9lead motors internal connections vary from the delta motor. Ieee std 1122004, ieee standard test procedure for polyphase. Tan delta test sets, which come as both standalone and vanmounted systems, are increasingly common components in todays test procedures. Technical library to guide electrical testers megger uk.
Insulation resistance test insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail. Work permit shall be prepared prior to start any activities. The resistance under test is connected between test terminals l and g the generator handle is then steadily turned at a uniform speed till the pointer gives a steady reading. Page 1 b a k e r i n s t r u m e n t s mtr105 rotating machine tester user guide page 2 megger ltd reserves the right to alter the specification of its products from time to time without notice.
The following sections of the ansineta standard for acceptance testing specifications for. This method will ensure that the separate windings. Test interphase resistance by disconnecting the leads from each terminal with a flathead screwdriver, then touch any two terminals with the two probes. In this video you will find out how to test 3phase induction motor. Timeresistance testing method this method is fairly independent of temperature and often. Ieee std 1122004, ieee standard test procedure for. Due to heat, vibration, and limited space, the insulation on motor windings is the weak link. The above variables should be controlled as much as possible to promote accurate insulation resistance measurement data.
347 1495 589 360 926 636 872 1168 1001 1162 689 685 1243 764 256 1232 1236 412 395 1451 1502 1460 1074 204 30 1507 350 744 526 901 645 539 694 57 1319 642 53 519 598 614 638