To accomplish this, a test procedure should be established and used consistently over time. The procedure of the insulation resistance test are given below first, disconnect all the line and neutral terminals of the transformer. 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. Note that the megger can check for faults to the motor iron, but not short. 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. If a fraction of current flows, it can be measured by these highly sensitive meters. 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.
Test performed so performed to know the insulation resistance value is. Tan delta diagnostic high voltage test equipment megger. How to meg a motor with a megohmeter checking motor condition. You can test your motor insulation with the help of a megger. 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 checked by touching the free ends of the leads together while the megger button is pressed on to check for zero. Megger leads are connected to lv and hv bushing studs to measure insulation resistance ir value in between the lv and hv windings. 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 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.
How to use a megger to measure and test motor insulation. You can then perform the following insulation resistance tests. 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. Additional notes about using a megger insulation tester 33. This current usually at an applied voltage of 500 volts or more is measured by the ohmmeter, which has. Meggers complete guide to electrical insulation testing pdf. 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. In this video you will find out how to test 3phase induction motor. Figure 4typical record of insulation resistance of a mill motor. Readings should be within the specifications provided by the manufacturer. Due to heat, vibration, and limited space, the insulation on motor windings is the weak link. Coils ii, iii, and iv are permanently connected and cannot be separated. 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 motor under test must be powered down and disconnected from all equipment and wiring not included in the test. Standard for acceptance testing specifications for. On a good motor, a megger reading between phases will show a short. All test leads, probes and crocodile clips must be in good order, clean and with no broken or cracked insulation. Connect the megger ground lead to the same ground plane the motor is connected to. When the test terminals are open, the resistance to be measured is infinite. The complete guide to electrical insulation testing.
We are testing the motors insulation, more specifically between the motor windings and the motor casing. How to test three phase ac motors learning electrical. Only megger approved test leads must be used with this product. Section d operating procedure follow the safety precautions of section b measurements on 600o 100ampere dlro range 1. Work permit shall be prepared prior to start any activities. Jul 06, 2016 the test generally applies between 100 and 5,000 v or more. Make sure the current connections are clean and tight. Note that the wyeconnected 9lead motors internal connections vary from the delta motor. Test interphase resistance by disconnecting the leads from each terminal with a flathead screwdriver, then touch any two terminals with the two probes. Test current adjustment test current indicated on the ammeter should. This is an insulation test of motor windings, commonly referred to as megging, to megger, or to meg a motor.
Figure 3typical scale on the megger insulation tester. A megger is an ohmmeter that measures resistance in the megohm scale. Aug 01, 2019 in addition to these uses of this test, the working principle, operation procedure, types, and applications have also been discussed. 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. If the motor is kept in a place with high humidity, a periodical inspection is necessary. How to megger a motor also known as an insulation test. Reverse side of card at right is used to record the test data. Understanding insulation resistance testing pdf 0206 rev. What is the procedure for testing insulation resistance in. Mar 28, 2018 in this video you will find out how to test 3phase induction motor. How to test a threephase motor with a megger hunker. In using the megger, a bit of a learning curve is involved. Rotate the end shaft approximately 30 degrees and test the motor again.
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. A guide to low resistance testing test equipment depot. Figure 2 typical megger test instrument hookup to measure insulation resistance. Megger insulation tester calibration procedure calibration. From power station to plug, megger test equipment helps you maintain the electrical network, monitor its condition and maintain supply to your customers. 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 megger technical library provides access to a range of additional content and resources such as technical guides, application notes and more. This current usually at an applied voltage of 500 volts or more is measured by the. Apr 09, 2017 a megger is used to verify the integrity of the insulation for safety reasons. Jan 16, 2016 this is an insulation test commonly referred to as megging, to megger, or to meg a motor. Megger and bridge test of motor cr4 discussion thread.
Polarisation index is the ratio of insulation resistance at 1 minute to 10 minutes. Megger leads are connected to lv and hv bushing studs to measure insulation resistance ir. To properly test this type of motor, remove the wirenuts joining leads 4 and 7, 5 and 8, and 6 and 9. Connections and turnon connect the test sample to the terminals as shown in figure. Another test we might do is called a polarization index test. Push the test button of the megger to generate the voltage.
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. The following sections of the ansineta standard for acceptance testing specifications for. 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. Connect the megger hot lead to a motor winding lead. 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. Ieee std 1122004 revision of ieee std 1121996 ieee standard test procedure for polyphase induction motors and generators sponsor electric. Technical library to guide electrical testers megger uk. Curve b shows same values corrected to 20c see page 22, giving a definite downward trend toward an unsafe condition. A megger is used to verify the integrity of the insulation for safety reasons.
In an industrial facility, the recommended procedure is to perform periodic tests and record. Megger insulation tester calibration procedure megger insulation tester is measuring resistance by generating a voltage. Aug 16, 2014 the procedure of the insulation resistance test are given below first, disconnect all the line and neutral terminals of the transformer. This is an insulation test commonly referred to as megging, to megger, or to meg a motor. Ieee std 432000 recommends a procedure for measuring insulation resistance of armature and field windings. Here we are showing you one verified brand new motor vs one that has been taken out of service. Com 99 washington street melrose, ma 02176 phone 7816651400 toll free 18005178431 visit us at.
Safety, hazard and warning symbols on the instrument. Mar 26, 2017 push the test button of the megger to generate the voltage. Timeresistance testing method this method is fairly independent of temperature and often. Ieee std 1122004, ieee standard test procedure for. Any help would be m megger testing procedures ieee electrical code issues engtips. 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. Megger is also called as a megaohmmeter and is a device used for the testing of insulation resistance of a cable.
Select a voltage to apply to the motor using an output from the megger that is higher that the. Insulation resistance test insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail. In addition to these uses of this test, the working principle, operation procedure, types, and applications have also been discussed. Megger leads to be connected to lv and hv bushing studs to measure insulation resistance ir value in between the lv and hv windings. To test a motor, use a megger megohm meter to test the insulation of the internal motor windings. The correct settings, connection procedures, test durations and safety precautions must be implemented to avoid damaging the equipment or possible electrocutions. Jul 17, 2017 release the push button on the megger or stop the cranking of the meter. The above variables should be controlled as much as possible to promote accurate insulation resistance measurement data. Initial and date the results of the following instructions and tests on attachments to this procedure. Using ohms law vir, we can compute the value of the resistance. 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. This is important, because the highvoltage current in threephase systems is far more lethal than a mere lowvoltage shock received in residential setting.
First we will disconnect all the line and neutral terminals of the transformer. 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 procedure of insulation resistance test or megger test are given below. All safety materials and equipment warning signs, barricades, fire extinguisher, etc. Some unknown facts was presented at the 2020 neta powertest conference in chicago, il. Using the megger to test a threephase motor is rather easy, though the safety hazards for this procedure are quite high. Megger has offered a 10 kv insulation resistance tester since 2001. If you want to test a 480v motor, then the voltage required would be v with a reading of 2m ohms or more. Well learn how to identify windings, check windings resistance and insulation resistance. Threephase dualvoltage motor insulation resistance testing.
431 495 30 1188 625 821 1164 184 257 14 1523 1149 1362 483 1108 78 568 35 631 128 747 870 195 569 168 337 1185 831 938 698 684 1311 693 965 789 1404 227