Jul 17, 2017 a visual inspection of the motor and associated connections are important, if no obvious faults are seen you can test the 3 phase motor. Threephase motor troubleshooting free download as pdf file. This article describes ac electrical motor troubleshooting. However, all three phase motors that run continuously in air conditioning or large freezer systems are susceptible to overheating if there is a voltage imbalance in one of the phases.
All you need is to connect the motor directly to a threephase ac power supply. If the voltage is present and correct, the motor is assumed to be the. Most times, if a motor is failing it will be replaced immediately. Maintenance and troubleshooting three phase induction motor. These motors run conveyor belts, pumps, fans, and many other applications.
Unbalanced voltage three phase only check the voltage at all phases. The single phase induction motor resembles, threephase, squirrelcage motor except that, single phase induction motor has no starting torque and some special arrangement have to be made to make it as self starting. Threephase motors are normally used in commercialtype operations. Single phase induction motor double revolving field theory the threephase induction motor starting torque inversely depends on the slip this implies that a small positive slip 0.
Lecture 6 three phase induction motors cairo university. Working through the system motor to disconnect,overloads, contactor and fusses. 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. All about motors page motor protection 83 notes on engineering 815 circuit documents 819 power supply 821 control circuit supply 824 contactor markings 825 directonline start of threephase motors 826 control circuit devices for directonline start 834 stardelta switching of threephase motors 835. A threephase induction motor problem enginuity systems. The singlephasing being a prevalent external fault, arises when one phase out of a three phase motor is suddenly opencircuited during machine operation 3. Troubleshooting three phase electrical motors kindle edition by brittian, l. A singlephase motor can be operated by simply connecting it to a singlephase power supply via the supplied capacitor. The threephase induction motor is the extensively used for various kinds of industrial drives. Single phasing three phase only check the current at all phases. The following examples show the rating plates for two motors with a motor shaft output of 4 kw and the respective connection circuits on a threephase ac network. In troubleshooting a motor you may need to verify that the motor lead numbers are correct, and that there have been no electrical faults that create short circuits between the different phases. Be careful it can hurt to tangle with a three phase motor. This troubleshooting guide can also be applied to other types of three phase induction motors.
Oct 27, 2008 in troubleshooting a motor you may need to verify that the motor lead numbers are correct, and that there have been no electrical faults that create short circuits between the different phases. The rotor is often called a squirrel cage because it consists of a circular network of bars and rings that look a bit like a cage connected to an axle. Be careful it can hurt to tangle with a threephase motor. The remaining steps below are different, depending on whether you have a y or delta connected motor. Compared to singlephase motors, its unusual for a threephase motor to be in a lockedrotor situation. If the cause of the overheating was not located during steps 1 and 2, proceed with causes 7a. The table below gives the commonly encountered problems in 3 phase squirrel cage induction motors, cause of problems and what remedy to apply to bring the motor back to production. Electrical troubleshooting textbook schoolcraft publishing. Threephase motor and drive system and common problems. The stator consists of a ring with three pairs of coils, evenly spaced around the rotor. Troubleshooting threephase electrical motors, brittian, l.
I would appreciate some guideance on how to troubleshoot a 25hp motor that is not running. Threephase dualvoltage motor insulation resistance testing. Singlephase motors are found in a long and diverse list of devices like washing machines, mechanical clocks and generators. Reduce the load or replace the motor with one of greater capacity. Despite the fact that the three phase motor has more phases than the single phase motor, the single phase motor is a much more complex machine. The rotor terminals are connected to three slip rings which turn with the. First, the drive input is the ac power entering the drive from the mains second, the drive and its output, where the ac to dc converter, the dc filter, and the dc to ac inverter provide the three phase power to the motor how to troubleshoot motors and drives, starting at the inputs. My friend called and said his pump motor was out and could i take a look at it. Motors are susceptible to the gradual failure of their insulation resistance. How to test three phase ac motors learning electrical. How to troubleshoot a 3phase electric motor hunker. The very first thing that you should do before starting any type of maintenance on a motor is a visual inspection, a lot of times the trouble can be found just by looking, because if the problem is that bad then it should be very obvious by observation. This situation often develops when theres an uneven distribution of single phase loads, either from a nearby panel or throughout the premises.
Three phase transformers 34 2 inoperative parallel connections of three phase transformers 34 3 transformer gasket application summary 96 4 vertical groove compression for. An electrical motor is an electromechanical device which converts electrical energy into mechanical energy. Put different colored tape on the wires in each group to keep the groups separate. If the motor doesnt rotate in two phase operation, find the reason for phase loss and eliminate it. If in the input circuit, correct the single phase condition. Use features like bookmarks, note taking and highlighting while reading troubleshooting three phase electrical motors. These types of motors are known as selfstarting induction motors.
The model created by rmxprt will then be used as an input for empulse as a basis for performing more detailed analysis and for increasing the accuracy of the performance pre. If there is a reading, the motor may be bad or it is a different type of motor other than an ac induction. Take input voltage to the motor using the volt ohmmeter. A successful salesman for general electrics motor division once remarked to one of your instructors that, when asked by a customer how a motor. If the motor is used in an application that is critical to the operation or production, testing is usually limited to checking the voltage at the motor. The very first thing that you should do before starting any type of maintenance on a motor is a visual inspection, a lot of times the trouble can be found just by looking, because if the problem is that bad then it should be very obvious by ob. Rotary phase converter ar5f floor unit 5hp made is usa. Maintenance safe maintenance practices performed by qualified personnel are imperative. The stator or the stationary part consists of three phase winding held in place in the slots of a laminated steel core which is enclosed and supported by a cast iron or a steel frame as shown in fig. Examine the motor s electrical connections and terminals. Because of their industrial use, if they are receiving the correct voltage, they. W download it once and read it on your kindle device, pc, phones or tablets. Unlike a 3 phase induction motor, a single phase induction motor is not self starting but requires some starting means. Apr 24, 2017 a three phase motor has two main parts.
May 31, 2018 today, were starting on a 3 phase motor and vfd upgrade for the grizzly g0602 lathe. Threephase motor troubleshooting electric motor fuse electrical. All threephase units are highstartingtorque motors and are capable of restarting against a load. If the motor is not in operation for a long period one week and above after installation or has been in operation but stopped for a period of time, the following precautions must be taken. Do not lift both the motor and driven equipment with the motor lifting means. The three phase induction motor is the extensively used for various kinds of industrial drives. Here we are giving you only overview on 3 phases induction motor. Check the reason for the unbalanced three phase power supply, if it is caused by the power voltage or the motor itself.
The torque developed at the shaft of a 3phase motor is constant, less vibration in machinery powered by 3phase motors. If the motor doesnt rotate in twophase operation, find the reason for phase loss and eliminate it. Explain how to identify external leads that have become defaced. Basics, maintenance, and diagnostics vii contents continued page 4. Check the reason for the unbalanced threephase power supply, if it is caused by the power voltage or the motor itself. If a single phase condition exists, correct the problem. Three phase dualvoltage motor insulation resistance testing three phase dualvoltage motors are used for most daytoday operations in todays industrial plants. Ac induction motors are also the most common motors used in main powered home appliances. The basic steps in ascertaining the health of a threephase ac motor are given below. Several additional components are necessary to operate the single phase motor. Troubleshooting threephase motors the extent of troubleshooting a 3o motor is dependent upon the motors application. Generally speaking, threephase motors are less troublesome than singlephase motors, having no starting relays or capacitors to deal with.
A single phase induction motor is very similar to a 3 phase squirrel cage induction motor. Nominal supply voltage, current, and frequency are the characteristics of the voltage supplied. The induction motor stator resembles the stator of a revolving field, three phase alternator. However, troubleshooting a 3 phase power motor can actually help you fix the problem and get it working again. Threephase dualvoltage motor insulation resistance testing threephase dualvoltage motors are used for most daytoday operations in todays industrial plants. Capcom phase converter for 3hp motor 35hp, digital phase converter, 1 phase to 3 phase. Before troubleshooting the 3 phase induction motor, we must have to know about the 3 phase induction motor, star delta starter and its connection diagram. Demonstrate how to conduct a balancedcurrent test on a three phase, yconnected winding. Single phase motors are found in a long and diverse list of devices like washing machines, mechanical clocks and generators. That way you can rule out the starter and all the conductors to the motor.
Use features like bookmarks, note taking and highlighting while reading troubleshooting threephase electrical motors. Help troubleshooting single phase motor electrical. List the symptoms of a reversed phase in a three phase winding. Set the voltage setting of the insulation resistance tester to 500v. If not, check supply circuitry, breakers and condition of the motor s power cord. Troubleshooting threephase electrical motors kindle edition by brittian, l. All about motors page motor protection 83 notes on engineering 815 circuit documents 819 power supply 821 control circuit supply 824 contactor markings 825 directonline start of three phase motors 826 control circuit devices for directonline start 834 stardelta switching of three phase motors 835. The video tutorial is essentially a part of the basic electrical and electronics engineering. Every good electrician knows the lead numbering sequence of three phase motors, or he has diagrams available for ready reference. Demonstrate how to test for an open circuit in a split phase motor. This 3 phase motor is also called as an asynchronous motor. Rotary phase converter ar5 5 hp 1 to 3 three ph made is usa. Nov 27, 2019 an electrical motor is an electromechanical device which converts electrical energy into mechanical energy.
The threephase ac induction motor is a rotating electric machine that is designed to operate on a threephase supply. Well talk about the motor and vfd and wire it up on the bench for testing before we tear into the lathe. By performance characteristics, we mean the nameplate ratings e. Repairing and reusing a 3 phase power motor is much more responsible than throwing away a motor that could be used with minor repairs. Examine the motors electrical connections and terminals. It includes troubleshooting procedures for control circuits and combination starters and explains troubleshooting practices on dc and ac motors, identifying unmarked leads on threephase delta and yconnected motors, and. Several additional components are necessary to operate the singlephase motor. If there is excessive dirt buildup, clean the motor. How to troubleshoot threephase electric motors, like if unable to start or overheats. In its simplest form, the threephase, random wound stator winding process consists of removing an existing winding from a stator and replacing it with a winding that duplicates the original winding performance characteristics. Despite the fact that the threephase motor has more phases than the singlephase motor, the singlephase motor is a much more complex machine. The motorspecified voltage must be present on all three phases. The best way to know for sure is check the voltage at the motor on all three legs. How to troubleshoot 3 phase motor with multimeter youtube.
The electrical troubleshooting textbook covers use of schematic diagrams, determining sequence of operation, and the use of building diagrams and singleline diagrams. A threephase induction motor problem this application note describes how to set up, solve, and analyze the results of a twopole, threephase induction motor using rmxprt. Pdf causes and effects of singlephasing induction motors. From a such a system, power can be supplied as single phase load connected between a line and neutral or three phase load connected between all three lines. If voltage is less than 10% of the motors rating contact power. Follow the steps below to check for the most common problems for threephase motors. A wound rotor, has a 3 phase winding similar to the stator winding. Its connected to an old furnas drum switch to give it reverse. In the case of three phase ac alternating current operation, the most widely used motor is a 3 phase induction motor, as this type of motor does not require an additional starting device. It would not be unusual for a motor to single phase itself to death from a blown fuse, especially if the thermals were not correct.
The motor specified voltage must be present on all three phases. Single phase motors have only two power source supply lines connected. Always have an expert check the motor windings to determine whether the single phasing occurred in the input circuit or in the motor windings. How to troubleshoot motors and drives, starting at the inputs. The principle of operation of this motor is based on. The auxiliary winding is switched in series with a capacitor and possibly a centrifugal switch. The single phase stator winding produces a magnetic field that pulsates in strength in a sinusoidal manner. In the illustration, the motor is connected as a three phase load and the socket outlets and lamp as single phase loads.
1071 1211 708 927 386 845 1027 647 922 719 850 486 1242 379 43 1458 876 78 1473 217 986 1411 620 316 892 684 897 225 1202 1267 1450 806 286 948 1320 786 165 1147 271 427 125 1229 138 1135 339 1473 888 624 334 1373 543