How To Repair Starter Overload

Have a step-past-pace arroyo to analyze motor starting issues

When troubleshooting a faulty electric motor, time (or in this instance downtime) is money. This notion was drilled into my head in my early years and has proven itself over and over again. Isolating the problem in the shortest amount of time saves plush downtime (and perhaps fifty-fifty your job). The other indicate that has been permanently burned into my consciousness involves a different type of self-pres...

August 1, 2005

When troubleshooting a faulty electric motor, fourth dimension (or in this example downtime) is money. This notion was drilled into my head in my early years and has proven itself over and over once again. Isolating the problem in the shortest amount of time saves costly downtime (and mayhap even your task).

The other point that has been permanently burned into my consciousness involves a different type of self-preservation: ever control the electrical circuit you are troubleshooting by following proper lock-out/tag-out procedures. Observing prophylactic maintenance procedures must e'er be given proper attention.

For these reasons, it is imperative that the maintenance electrician, technician or engineer uses a troubleshooting methodology that enables them to isolate the problem in the shortest amount of fourth dimension. Still, the logical procedure of elimination used to place the root cause of an air conditioning motor's malfunctioning tin differ. At times it is more effective to start at the motor and piece of work back to the starter; in other instances information technology'due south amend to begin at the starter and move towards the motor. My full general preference is to brainstorm at the excitation source and work towards the motor.

For the purpose of this article, I'm addressing typical starting issues only. Running problems tin can exist numerous and varied, and in many cases tin be traced all the way back to improper motor specification for a particular application.

Starting bug with three-phase air-conditioning anterior motors can be grouped into iii primary categories: voltage source problems; motor excitation problems, which include the motor starter and air-conditioning drive; and application or mechanical problems.

Troubleshooting voltage source issues

Use a procedure of elimination to isolate and diagnose voltage source problems. Refer to "Voltage source issues flowchart" on page 66, which illustrates the steps of the post-obit troubleshooting procedure:

1. Check the incoming power to the motor starter. Using a digital multimeter (DMM) set to voltage mode, verify that all three phases of electrical potential are present. If one or more than of the phases is missing, disconnect the main voltage source (incoming ability disconnect switch) and supersede the incoming ability fuses or reset the motor-control excursion breaker.

3. Prior to restoring the primary voltage source, set the DMM to continuity mode (ohms) and verify at the motor starter line contactors that there is not a phase-to-phase short or a phase-to-ground short. If there is a short or basis on the line side of the starter, replace the starter contactor and verify that the short or ground is now clear. Next, verify that the load side of the circuit does not accept a phase-to-stage short or a phase-to-ground short. This final continuity check will too verify that the motor line does not take an open phase. If the motor starter line circuits are articulate, the problem is on the load side of the starter. Follow the circuit to the load side of the starter.

5. Try to reset each of the motor thermal overloads on the motor starter. If whatever one of the overloads have tripped y'all will exist able to experience when the overload resets while pressing the reset pushbutton. If you completed the continuity check of the load side of the motor contactor described in Step 2 and the circuits are clear, restore the incoming power and get-go the motor.

7. If the continuity check on the load side of the contactor is shorted stage-to-phase, phase-to-footing or open phase-to-phase, then follow the ability circuit to the motor.

9. Disconnect the incoming motor leads at the ac motor electrical conduit box. Check the motor starter leads for a phase-to-stage or a phase-to-ground short. If either of these two problems exists, bank check the motor atomic number 82 wiring. If the motor starter leads are clear, move on to the motor.

11. With the motor still disconnected, check the motor leads for a phase-to-phase or a phase-to-ground short. There is a high probability that if at that place were no problems establish previously in the circuit, the motor has a stage-to-stage brusque or a short-to-footing mistake. If you take verified a phase-to-phase or phase-to-ground fault in the motor, replace the motor and start the organization.

13. If there appears to be no trouble with the air-conditioning motor or its power circuit, then examination the motor insulation with an insulation tester. The insulation exam determines if the motor windings are "breaking downwardly" during running weather.

15. If the insulation test results are negative, a mechanical problem is probably causing the motor overload. Uncouple the motor from the mechanical load and showtime the motor. If the motor runs, the problem is in the mechanical drive train. If the motor does not run and the motor overloads trip again, the trouble is in the motor bearings.

16. • Troubleshooting control circuit issues

    • You tin can also use a process of elimination to isolate and diagnose control circuit problems. Refer to "Control circuit problems flowchart" on page 68, which illustrates the steps of the post-obit troubleshooting procedure:

      1. If all three phases of electrical voltage were present when y'all performed Stride i of "Troubleshooting voltage source problems," then the motor starter overload and control circuits should be checked. Determine if all or any of the motor starter overloads are tripped by pressing the motor overload reset pushbutton. If the motor overload(s) were tripped, endeavor to restart the motor. If the problem was isolated to the motor overload(southward), the motor should run. If the motor overload(s) trips over again, return to Step v of "Troubleshooting voltage source bug" to determine if the problem is a motor trouble or load problem.

      3. If the motor overloads are not tripped, verify that the starter command circuit has the proper secondary voltage using a DMM ready to voltage mode and the advisable range. If the proper voltage is not present, disconnect the motor starter's incoming power supply.

      5. Using the DMM in continuity manner (Ohms), verify the integrity of the control voltage transformer fuse. Supervene upon the fuse if blown, and

      7. identify the motor starter command circuit trouble. If the starter command transformer fuse is proficient, keep to Pace 8 of this troubleshooting procedure.

      9. Disconnect the motor starter contactor coil and check for a short, ground or open circuit. If a curt or basis is establish, replace the motor starter contactor coil and start the motor.

      11. If the motor kickoff contactor gyre is good, with the curl notwithstanding asunder, bank check the control circuit wiring to the contactor coil. If a short or ground is detected, disconnect the field wiring excursion to the motor starter to decide if the problem is internal to the motor contactor overload circuit(s) or in the field control wiring.

      13. If an electric ground is located in the motor starter overloads excursion, replace the motor overload(south). Once the failed motor overloads accept been replaced verify excursion continuity, reconnect the starter coil and command field wiring, restore incoming power and commencement the motor.

      15. If an electrical ground is not located in the motor starter overload excursion, the problem has been isolated to the control circuit field wiring. Articulate the ground in the field wiring excursion. Then reconnect the motor starter scroll, overload circuit and field wiring, restore incoming ability and beginning the motor.

      17. If you make up one's mind that the starter control voltage is intact and present, suspect a potential open circuit in the motor overloads or control circuit. To check for an open circuit, outset disconnect the incoming ability supply, and using the DMM in continuity mode (Ohms), verify the circuit integrity of the motor overloads control excursion (secondary contacts). If the motor overloads command circuit is skillful (all NC contacts have continuity), then the field control excursion to the motor starter is the trouble.

      19. To troubleshoot the field command circuit to the motor starter, check continuity across the device that supplies the starting time bespeak to the motor starter, which could be a PLC contact closure, relay contact closure or start/end pushbutton excursion. After the control circuit trouble has been located and corrected, restore the incoming power and start the motor.

      20. • AC bulldoze excitation — bulldoze faults

          • When a bulldoze error occurs in an air-conditioning drive and motor application, make up one's mind if the fault is a motor, drive or application problem.

            The diagnostic applied science offered in modern ac drives can assistance you troubleshoot many bulldoze bug. Manufacturers often include internal diagnostic capabilities in the drive's microprocessor control. By using these drive fault diagnostics, yous can easily determine and remedy the fault.

            Some of the most common problems related to integrating an ac drive with an air conditioning motor are listed in the table "Typical ac drive faults." However, there are may other possible bulldoze faults associated with motor/drive tuning, application requirements, communication errors, external device errors and initial programming errors. If you are still unable to locate the source of the trouble after ruling out the causes listed in the tabular array, contact the equipment manufacturer or your local distributor for farther diagnostic assistance.

            The majority of ac motor and drive problems tin be solved past using the drive manufacturer'southward manual. Each drive error that is monitored and annunciated by the drive'due south microprocessor is listed in the troubleshooting department of the manual. If yous cannot locate your manual, contact your local manufacturer's representative or refer to the manufacturer'due south website to download a re-create.

            AC motor and drive technology

            The application of ac motor and air conditioning drive technology is becoming much more prevalent in applications that were previously done with dc technology (variable speed applications) or across-the-line starters (historically constant speed applications used on fans and pumps). With the development of dissimilar air-conditioning drive technologies, such as soft start, 5/Hz, open loop vector and closed loop vector drives, this trend will likely continue — and if annihilation, increase.

            The ability to apply the right ac motor engineering science in the right application ensures that the motor/excitation technology used volition provide trouble-free operation for many years. The ability to develop and execute a logical troubleshooting methodology when equipment failure does occur will assure that your process achieves the maximum amount of uptime.

            Typical ac drive faults

            Mistake	Description	Possible causes
            DC bus undervoltage	Apparent low supply voltage condition	%%Betoken%% Incoming voltage is lower than the drive's rated incoming voltage requirement (ordinarily
            		%%POINT%% Bulldoze acceleration is besides brusk
            DC passenger vehicle overvoltage	Credible loftier supply voltage condition	%%POINT%% Incoming voltage is higher than the bulldoze's rated incoming voltage requirement (commonly
            		%%POINT%% Bulldoze deceleration is too curt
            		%%POINT%% Ability gene correction capacitors on the incoming electric line
            Overcurrent	Drive output current that exceeds the maximum bulldoze current output rating	%%Bespeak%% Phase-to-phase short
            		%%POINT%% Locked rotor
            		%%Bespeak%% Dispatch also short
            		%%POINT%% Load too large
            Motor overload	Bulldoze output current exceeds the current rating of the motor	%%POINT%% Load too large
            		%%Point%% Acceleration/deceleration too short
            		%%Signal%% Incorrect V/F pattern
            		%%POINT%% Motor-rated current incorrectly loaded into drive
            Bulldoze overload	Drive output current exceeds the current rating of the drive	%%POINT%% Load too large
            		%%Signal%% Acceleration/deceleration as well short
            		%%Signal%% Incorrect V/F blueprint
            		%%Point%% Bulldoze is sized too small for motor application

            More Info:

            Patrick Due east. Owens is a Technology Manager at Kaman Industrial Technologies. If you have questions about motor troubleshooting and maintenance you may contact Mr. Owens directly at patrick.owens-kit@kaman.com . Article edited by Jack Smith, Senior Editor, Institute Engineering science magazine, (630) 288-8783, jsmith@reedbusiness.com .

            Typical motor failures

            Typical failures that occur with ac motors include:

            Motor begetting failure — Motor bearing failure is the #i crusade of motor failures and tin exist acquired by lubrication problems, contamination, bearing electric current, shaft misalignment or side loading

            Single-phase motor winding failure — One phase is open in the motor circuit, which can be caused by a blown fuse, open contactor, open motor pb or bad electrical connections

            Phase-to-phase or plough-to-turn motor winding error — The motor winding is shorted phase-to-phase or turn-to-turn considering of motor insulation failure, which tin can be acquired by contaminants, abrasion, vibration or voltage surge

            Winding grounded fault —The motor winding is shorted from the motor winding to the grounded motor frame because of motor insulation failure, which can be caused past contaminants, abrasion, vibration or voltage surge

            Motor phase harm —Motor phase damage typically occurs from unequal stage voltages, which can be caused past an unbalanced load at the ability source, poor connections or high resistance in a single leg of the motor excursion

            Motor winding harm —Motor winding impairment (all windings) is caused by the thermal deterioration of the insulation in all phases, which is acquired by motor overload or over/under voltage situations. Switching ability circuit, capacitor discharges, or solid-state ability devices can also cause this type of motor winding damage

Do you have experience and expertise with the topics mentioned in this article? Yous should consider contributing content to our CFE Media editorial team and getting the recognition you lot and your company deserve. Click here to start this process.

Search Products And Discover New Innovations In Your Industry

Past using this website, you agree to our use of cookies. This may include personalization of content and ads, and traffic analytics. Review our Privacy Policy for more information. ACCEPT

Source: https://www.plantengineering.com/articles/take-a-step-by-step-approach-to-analyze-motor-starting-problems/

Posted by: littlediesse.blogspot.com

Share this post