Practical Troubleshooting, Maintenance &. Protection of AC Electrical Motors & Drives. Revision Web Site:haakoopmacyding.cf E-mail: [email protected] . Electric Motor. Maintenance and. Troubleshooting. Second Edition. Augie Hand. Mc. Graw. Hill. New York. Chicago San Francisco. Lisbon. London. Madrid. This Electric Motor Repair Course is designed to provide the student with practical information for winding,. repaiT'ina, and troubleshooting alternat:ng current.
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Electric Motor Maintenance and Troubleshooting, 2nd Edition [Augie Hand] on haakoopmacyding.cf *FREE* shipping on qualifying offers. Publisher's Note: Products. Chapter С Maintenance & Troubleshooting. 47 Determine if the problem is mechanical, electrical, or software-related. Motor Maintenance and Inspection. electric motor's usage and failure modes The troubleshooting procedure. should be the prime concern when troubleshooting or doing routine maintenance .
Some sparking is normal within many electric motors including table saws and drills, but no sparks ought to be seen exiting the device or its motor for obvious safety reasons. Typically when I've seen sparks spraying out of a drill or table saw I've found that the motor brushes need replacement.
Electric Motor Maintenance and Troubleshooting, 2nd Edition, 2nd Edition
A burned commutator in the electric motor is often the root problem. Some light cleaning of the commutator may be needed. Take care not to score it. Remove the motor armature and sand it with very fine emery paper. Inspect the amature while cleaning it.
Example of an electric motor test: Measure the resistance between each lead wire with a multimeter or VOM. The multimeter should be set in the X1 range. When the resistance between each lead wire are those listed in the specifications for your equipment the fan motor should be normal.
Zero resistance or infinite resistance are indicators of a problem. The main or primary windings are directly connected to the power lines while the motor in running. The second windings are usually thinner wires physically offset from the main windings inside the motor. The purpose of the secondary windings is to provide directional information and an initial strong kick to get the motor started turning.
Once the motor is started, the main or primary windings can keep the motor running just fine. Less common, these secondary windings are directly powered from the power lines through a run capacitor that provides a continuous time or phase shift to the windings. This switch is usually behind and part of the connection plate where you attach the power cables in the end of the motor. Any little piece of dust can keep this switch from closing when the motor is stopped.
Simply knocking this one little dust particle off makes the repair, and the motor will run fine henceforth. Most of the time you have to pull the back end of the motor off to get to this switch. Reversing the direction of the current in the secondary windings reverses the direction of the motor. This can usually be done by switching the leads to the secondary windings. Sometimes one of the secondary leads is attached to a primary windings and you have to dig into the windings to find it and separate it out.
You can download electronic phase converters to generate a third leg which work reasonably well, but generally works for just one electric motor at a time. The converter must be somewhat closely matched to the motor in size.
Troubleshooting electric motors help...
It converts AC to DC, then creates an artificial third leg electronically. You can use any 3 phase motor to generate the third leg if you can get it started. I have read about people using a small single phase motor to get a bigger 3 phase motor going, or using a pull rope wrapped around the motor shaft to pull start the big 3 phase motor. Once running, a 3 phase motor will generate a third leg which you can use to run other 3 phase motors. Y wound motors work much better than a Delta wound motors in this approach.
I think you can use a capacitor to the third leg much like single phase motors to generate enough of a phase offset to get the 3 phase motor started.
The shocked client may have used the 3 phase motor to run the compressor directly. He probably needed a good unloader to prevent the motor from getting bogged down by the compressor until the motor got up to speed.
The center of the Y windings may have been attached to the neutral or ground wires, but probably would be shifted towards the third leg.
You can download commercial rotoconveters designed to generate 3 phase from 2 phase. They look like a motor with no output shaft and have an attached big box containing a batch of capacitors.
The rotating armature of a 3 phase motor on its own will generate a weak third leg that will probably be somewhat phase shifted towards the 2nd leg. The capacitors are attached between the first and third leg, which will generate a leading current towards the first leg, somewhat offsetting the shift towards the second leg.
The basics of motor testing
Adding a few more turns would generate a larger voltage output from the generated third leg. I have never taken a rotoconverter apart, so this is just a good guess.
You can run multiple 3 phase motors of different sizes simultaneously. The burnt smell is coming from the insulation varnish of the motor windings. Motor winding damage is possible under these conditions so winding tests should be conducted.
Dirt acts like a heat insulator and heat damage is the weakness of normal motor operation. Inspect the cooling fan and passages to ensure they are operational and free of blockage, respectively. Clean all surfaces with a rag and blow out or vacuum passages with a shop vac. Corrosion can damage motor windings as well as create high resistance wiring connections. If the corrosion is chronic, a motor rewind may be merited if the winding tests verify that winding damage has occurred.
Re-lugging the motor connection box terminals also may be required. Motor Winding Tests Once the motor is disassembled, and a thorough inspection of internal components has been conducted, testing the motor windings is done. This is where a maintenance history can prove its value.
Electric Motor Data Acquisition
What kind of service history is on record relative to the winding failures or abnormalities? Has the motor ever been rewound? If so, what was the cause of the failure? This information suggests what kind of motor winding tests are necessary. In some situations, motor winding tests beyond the ground insulation megger test may need to be conducted. Is there any evidence of overheating of the windings?
This may appear as burn marks, cracks, or, if catastrophic, exposed wire.
Severe damage would require rewinding the motor. Once again, look at the physical condition of the windings.
If they are dirty or corroded, clean the windings with a brush, hot water and detergents and a vacuum. Avoid using pressurized air because the force of the air may propel particles into the winding insulation and damage it.
Is there moisture on the windings? If so, prior to conducting any winding tests, the windings must be thoroughly dried out. Moist or wet windings will generally give false readings when conducting insulation tests so the windings must be dried first.
This is done by baking the motor windings in an oven until the insulation resistance is at least 10 megohms. If this does not work, consider revarnishing the motor first.
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Electric Motors and Drives: Fundamentals, Types and Applications, 4th Edition. Austin Hughes. Lynn Lundquist. About the Author Augie Hand had 30 years of hands-on experience in repairing and troubleshooting motors, followed by 15 years of giving seminars on the subject for electric motor repair shop technicians and in-house training for large industry maintenance technicians.
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I wanted more information on motors due to college courses I am currently taking. I jumped past DC and went straight into AC 3 phase.A number of diagnostic tools, such as clamp-on ammeters, temperature sensors, a Megger or oscilloscope, can help illuminate the problem.
The bearings should be cleaned with a lint free rag. Kenneth Kruger, R. As motors age, the current drawn generally rises because winding insulation resistance drops. Knowledge and skills in electricity, troubleshooting, and computer operation are necessary prerequisites to effectively assimilate basic PLC training. Additional time was spent at home studying the manual and writing programs.
The converter must be somewhat closely matched to the motor in size. The start winding is disconnected, usually by a centrifugal switch, when the motor is up to speed.
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