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motor starters and their troubleshooting.pdf
This document discusses motor starters, their components, and troubleshooting procedures. It describes the functions of motor starters as starting and stopping motors, providing remote control, and protecting motors. It explains the types of starters and components such as contactors, overload relays, and circuit breakers. It provides details on NEMA and IEC standards for these components. Finally, it outlines the steps for troubleshooting motor starters, including using lockout/tagout procedures, test equipment, and repair and restoration.
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motor starters and their troubleshooting.pdf
- 1. Motor Starters And Their Troubleshooting J Niranjan
- 2. J Niranjan Introduction toMotor Starters Functions of a Motor Starter Starting and stopping the motor (or other device) Provide remote control to the motor or heater Limit the current inrush Reverse the motor Control the speed of the motor Protect the motor from overloading/over-speeding overheating or ground fault conditions
- 3. J Niranjan Introduction toMotor Starters Types of Starters Direct On Line Starters (DOL) or Across the line Starters Reduced Voltage Starters – Achieved by means of 1) Solid State Devices (Soft-starters, VFD’s) 2) Auto Transformers 3) Reactors 4) Star/Delta connections
- 4. J Niranjan Components ofa Motor Starter MCCB Contactor O/L Relay Ground Fault relay CT’s for current indication Motor protection relay Pilot Lamp CBCT for E/f protection
- 5. J Niranjan Components ofa Motor Starter Main Contactor CPT Ground Fault relay Ammeter Pilot Lamp Auxiliary Contactor Power Transducer for remote indication Note: MCCB is not shown
- 6. J Niranjan Components ofa Motor Starter Contactors Definition: An electromechanical device that opens and closes a power circuit. Generally operated magnetically, providing remote control, but can also be operated manually. Power is controlled when the contactor’s contacts open and close. Function: To control motors (most common) and other power circuits (e.g. transformers, heaters, lights, and capacitors).
- 7. J Niranjan Components ofa Motor Starter Contactors There are two main types of contactors used in industrial applications — contactors designed to NEMA standards and contactors designed to IEC standards Traditional NEMA contactors are designed to meet the size ratings (00, 0, 1, 2 … 9) specified in NEMA standards. A NEMA contactor is designed by convention with sufficient reserve capacity to assure performance over a broad range of applications Traditional IEC contactors are designed to match a contactor to a load, expressed in both the contactor’s rating and expected life. IEC standards do not define standard sizes — the manufacturer can choose to apply any rating based on meeting the performance and test requirements of the IEC standards.
- 8. J Niranjan Components ofa Motor Starter NEMA Contactor IEC Contactor
- 9. J Niranjan Components ofa Motor Starter NEMA Contactors for various motor ratings
- 10. J Niranjan Components ofa Motor Starter NEMA Vs IEC Contactors for various motor ratings HP @ 460V NEMA Contactor Size IEC Contactor Size I Size 00 9A 2 5 Size 0 7.5 Size I I2A I0 I8A I5 Size 2 25A 20 32A 25 40A 30 Size 3 50A 40 65A 50 80A
- 11. J Niranjan Components ofa Motor Starter Let’s say that an application requires a contactor for a I5HP motor — if a NEMA device was being specified, a Size 2 contactor would be required. The Size 2 device has much greater capacity than is required for the application, it is capable of controlling a 25HP motor. However, if an IEC contactor is selected, a I5HP device could be specified. Thus a physically smaller, lower cost device can be got with IEC standard. IEC contactors are rated much closer to the ultimate switching capabilities and have much less “reserve capacity” than their NEMA counterparts. This in great part contributes to the small physical size of IEC contactors compared to NEMA contactors (of the same horsepower rating) but the life would be much lesser.
- 12. J Niranjan Components ofa Motor Starter OVERLOAD RELAYS Definition: Electromechanical device that prevents damage to a motor caused by excessive current. When an overload relay senses that a motor is overheating (eg. drawing too much current over a specific period of time), the overload relay will trip, removing power to the motor (by interrupting the contact or coil circuit). Function: To protect the windings of motors and the conductors to the motor against overload currents.
- 13. J Niranjan Components ofa Motor Starter Traditional NEMA thermal overload relays typically accept interchangeable, field installable heater elements. Each overload relay will accept different heater elements based on the maximum current rating of the overload relay or the contactor size if the overload relay is to be directly installed on the contactor. The heater elements are typically eutectic alloy (although bimetal constructions are also available), and are indirectly heated. Heater elements are available with trip Classes 10, 20, and 30. Traditional IEC thermal overload relays include integral, directly heated bimetal elements. Typically these overload relays have an adjustable current setting, marked in amperes. The minimum to maximum adjustment range is approximately 1:1.5 (ex. 10A to 15A
- 14. J Niranjan Components ofa Motor Starter NEMA Overload Relay IEC Overload Relay
- 15. J Niranjan Components ofa Motor Starter Trip Classes of IEC Overload Relays
- 16. J Niranjan Components ofa Motor Starter Overload Relay- Time Current Curves
- 17. J Niranjan Components ofa Motor Starter Motor Protection Circuit Breakers Definition: A circuit breaker that is assembled as an integral unit in a supporting and enclosing housing of insulating material. Thermal elements (various trip classes available, typically class 10) are ambient temperature compensated for precise overload protection of motor windings, and include phase loss protection.
- 18. J Niranjan Components ofa Motor Starter Function: Motor Protection Circuit Breakers are multi- function devices designed to: Manually control motors (most common) and other power circuits (e.g. transformers, heaters, and lights) Protect the windings of motors and the conductors of the motor against overload currents Protect motor circuit components (contactors, overload relays, and motors) and the conductors to the motor against short circuit currents Disconnect all of the motor circuit conductors simultaneously from their source of supply
- 19. J Niranjan Components ofa Motor Starter Short Circuit Protective Devices There are a number of choices of short circuit protective devices including fuses, molded case circuit breakers, and motor circuit protectors. Even though they are not “motor control devices” they are closely associated with and used with motor control devices. All Installation Codes and Standards dictate, a short circuit protective device is required in every motor branch circuit
- 20. J Niranjan Components ofa Motor Starter Short Circuit Protective Devices Fuses Definition: An overcurrent protective device with a fusible link that operates (one-time only) to open the circuit on an overcurrent condition. Function: Protect motor circuit components (contactors, overload relays, and motors) and the conductors to the motor against short circuit currents Protect the motor circuit conductors against overload currents
- 21. J Niranjan Components ofa Motor Starter Short Circuit Protective Devices Molded Case Circuit Breakers Definition: A device that is assembled as an integral unit in a supporting and enclosing housing of insulating material, designed to open and close a circuit by non- automatic means and to open the circuit automatically on a predetermined overcurrent (short circuit or overload), without injury to itself when properly applied within its rating. Function: Protect motor circuit components (contactors, overload relays, and motors) and the conductors to the motor against short circuit currents Protect the motor circuit conductors against overload currents Disconnect all of the motor branch circuit conductors simultaneously from their source of supply
- 22. J Niranjan Components ofa Motor Starter TYPE 2 CO-ORDINATION Type 2 Coordination means that a starter will not be damaged in the event of a short circuit fault. Following is the definition from IEC 60947-4-1: Type 2 Coordination: under short-circuit conditions, the contactor or starter shall cause no danger to persons or installation and shall be suitable for further use. The risk of contact welding is recognized, in which case the manufacturer shall indicate the measures to be taken with regard to the maintenance of the equipment.
- 23. J Niranjan Components ofa Motor Starter TYPE 2 CO-ORDINATION By specifying Type 2 Coordination, safety to personnel is enhanced because arc flashes resulting from short circuit faults can be eliminated. In addition to enhanced safety, Type 2 Coordination provides the following benefits: Reduced component replacement costs Increased productivity Simple device selection Component replacement costs are reduced because contactors, starters, and motor protection circuit breakers are protected against damage — so they don’t need to be repaired or replaced after a short circuit fault.
- 24. J Niranjan Components ofa Motor Starter It is simple to select the appropriate motor control devices that provide Type 2 Coordination - manufacturers provide easy to use tables that match the motor protection circuit breaker and contactor that will provide Type 2 coordination up to a specified short circuit fault current. The table provided by Siemens is in the next slide
- 25. J Niranjan Components ofa Motor Starter
- 26. J Niranjan Troubleshooting ofMotor Starters • COLLECT SCHEMATIC DIAGRAMS, SPECIFICATIONS AND TROUBLESHOOTING AIDS • PREPARE THE HWP • CONDUCT DIAGNOSTIC TROUBLESHOOTING This should be done in the following steps: Have the correct prints or drawings on hand Verify the meter is in good condition, no cracks in the leads, fresh batteries and recent calibration Put on the appropriate PPE. Carefully open the doors or remove the equipment covers Test the meter on a known external source Read the Voltage (or Absence) on the load side of the circuit breaker for the starter, phase to phase first, then phase to ground Check for control Voltage or any other Voltage (possibly from other circuits) within the starter Record the readings Upon completion of the troubleshooting or repair, close the doors and replace all covers—Do not leave energized equipment unattended
- 27. J Niranjan Troubleshooting ofMotor Starters • LOCATE THE POWER SOURCE AND REMOVE POWER This step amounts to de-energizing the circuit. The supply for the starter is likely the main circuit breaker. This is located in the module itself. Be sure the motor is stopped before opening the main disconnect—This will prolong the contact life of the disconnect switch contacts; if the motor is still running, stop it manually If the module needs to be removed, should be done following PPE table and standby person shall be present Verify that all power sources are absent from the starter—Any capacitors should be discharged and grounded • UTILIZE LOCKOUT-TAGOUT PROCEDURES
- 28. J Niranjan Troubleshooting ofMotor Starters • UTILIZE TEST EQUIPMENT TO TROUBLESHOOT AND ISOLATE CAUSE Troubleshooting of circuits necessitates using the proper test equipment within its ratings. Most low Voltage test equipment suited for industrial use is rated at 1000 volts dc. Different types of test equipment are used for different purposes. These test equipments include digital multi-meter, clamp on Ammeter, DLRO, Megger etc.
- 29. J Niranjan Tests onVarious Components •Main circuit breaker – Rarely is the problem here, however contact resistance should be tested with a DLRO, trip time can also be tested with a high current test set. •Control power transformer CPT—normally energized when circuit breaker is on. Check fuses and continuity of primary and secondary windings.
- 30. J Niranjan Tests onVarious Components Contactor coil Measure continuity with an ohmmeter (DMM). The values will vary depending on the contactor model. Some bigger sized contactors use a ‘DC’ coil and hence the AC control supply is rectified and fed to the coil. In this case the continuity cannot be checked Auxiliary switch contacts Measure continuity with DMM. Contacts should follow armature: The ‘NO’ contact (‘a’ contact – has a suffix number 3-4)makes with main , the ‘NC’ contact (‘b’ contact – has a suffix number 1-2)breaks when main makes
- 31. J Niranjan Tests onVarious Components Current Transformers Measure for continuity with ohmmeter, make sure leads are clean and tightly connected.
- 32. J Niranjan Tests onVarious Components Ground fault relay (Contd.) Ground fault relays must be manually reset. Causes of ground faults are moisture, insulation damage or deterioration, or unintentional connections of neutral and ground conductors downstream from the main service. In any case, the cause of the ground fault must be determined before the circuit is re-energized.
- 33. J Niranjan TEST PROCEDURES •SETUP A TEST CIRCUIT One of the best means of checking out the starter or any of its individual components is to set up a test circuit. A variac can be used to inject this control supply. In some MCC’s, there is a ‘test’ facility, which energizes only the control supply and can be used
- 34. J Niranjan TEST PROCEDURES •OPERATETHE TEST CIRCUIT There are some safety rules to follow when checking components with a test circuit. Warning: Whenever using an external Voltage to test a component in a starter, you must ensure that the device under test is isolated from all other, so there is no possibility of backfeed or accidental energization Test circuits are easily used and operated when the device is out of the starter and placed on the bench. However, in real world troubleshooting, it is not always practical to take a contactor or relay out of the MCC for testing. In fact, it is usually prohibitive.
- 35. J Niranjan Tests onVarious Components Isolate the Device— Great care must be exercised so that the component under test cannot energize another component, specifically, if you test the main contactor with an external 110 Volt supply, you don’t want the motor to actually start Watch for Interlocks- In a reversing starter, or a two-speed starter, the two contactors are electrically and mechanically interlocked so that only one can be closed at once. Again, avoid energizing an interlocked device. Even though there may be no electrical hazard (the input power will have de-energized) but the mechanical linkage can be damaged by the power of a large contactor.
- 36. J Niranjan REPAIR ANDRESTORATION •REPAIR CIRCUIT OR REPLACE DEFECTIVE COMPONENT Replace the defective device with a like device that is either new or known to be fully operational. If there is doubt, then the replacement unit should be tested before installation if possible. In most cases, any circuits or devices repaired, particularly feeders should be meggered to verify that no conductors are shorted or grounded. •CLEAR THE AREA AND REMOVE THE LOCKOUT As in the normal LOTO procedure, notify all affected personnel that the power is about to be restored. Remove any temporary grounds, barriers and warning signs and remove the LOCK OUT.
- 37. J Niranjan REPAIR ANDRESTORATION •RESTORE POWER Before inserting the fuses or closing the circuit breaker, be sure all controls are in the OFF or MANUAL positions so that equipment does not start up when the control circuit is energized. Using the proper techniques, close the CB (or install the fuses). Immediately verify that control power is present and within the proper Voltage range. (control fuses may blow due to CPT inrush and hence voltage checking is necessary) •TEST OPERATION Again, any affected personnel should be notified that the starter is about to be tested and that the motor will be starting. The motor should be brought on in the normal mode by remote controls.
- 38. J Niranjan REPAIR ANDRESTORATION •RESTORE SERVICE Provided that the operational tests are successful, then the control selectors can be set to the RUN or AUTOMATIC mode. When the control circuit has been restored, then is should be observed for proper operation. •DOCUMENT THE REPAIR, CORRECT DRAWINGS No job is complete until the documentation is done through 7i. Any changes made in wiring to accommodate new components should be marked in on the schematic diagram and highlighted in a different color ink (red). If required, a RCA (root cause analysis) should be conducted immediately.