Motor Maintenance Flashcards
(16 cards)
with reference to electrical motors
State the routine maintenance that is necessary
- Motor is tightly fastened to avoid vibration.
- Ensure Shaft is turning freely and bearings are correctly greased.
- Regular inspections such as cleanliness etc, casing fan.
- Ensure the motor is not overheating, so no hot spots.
- Regular on load testing.
- Balance Test
MORE
- Change Bearings and Seals
- Regular on Load Testing
- Clean Casing
- Clean and Check Fan
- Check Windings
- Check Terminal Box
- No Abnormal Noises
- No Vibrations
with reference to electrical motors
Describe the tests carried out to prove good electrical condition
Insulation Resistance Test
- Testing the quality of insulation between electrical conductors and earth or between conductors.
HOW
- Tested with a megger or an insulation resistance tester.
STEP BY STEP
- Phase to Phase (probe to 1 conductor, other probe to other conductor)
- Phase to Earth (probe to conductor, other probe to ships hull)
- Minimum Acceptable Value is 1mega ohm.
Continuity Test
- Testing if the circuit has continuity, which means if electricity can pass through without interruption.
HOW
- Tested with a multiimetre and checks weather the circuit is intact, no continuity = break or fault in the circuit.
STEP BY STEP
- Touch probes to both ends of the circuit.
- Beep/small resistance = continuity.
- No beep/infinite resistance = no continuity (open circuit).
Balance Test
- Resistance readings for each winding are taken, a good motor will show that the windings resistance readings should all be similar.
- Tested with a multimetre also.
Describe how you would overhaul an electric motor that has been flooded with sea water
1), Isolate the power supply.
2), Safely remove the motor from its mount.
3), Dismantle the motor
4), Clean rotor and stator with fresh water to remove salts.
5), Rinse and thoroughly dry all parts.
6), Re-varnish the dried stator.
7), Fit and grease new bearings during reassembly.
AFTER REASSEMBLY
- Continuity Test
- Balance Test
- Insulation Resistance Test
If test results are within parameters, the motor is ready for use.
Explain how to check the insulation resistance of the motor, stating the minimum acceptable value
Insulation Resistance Test
- Testing the quality of insulation between electrical conductors and earth or between conductors.
- Minimum Acceptable Value is 1mega ohm.
HOW
- Tested with a megger or an insulation resistance tester.
U1 V1 W1
U2 V2 W2
STEP BY STEP
First, Phase to Phase
U1 to V1 –> V1 to W1 –> W1 to U1
Second, Phase to Earth
U1 to earth –> V1 to earth –> W1 to earth
with reference to electrical motors
State the routine maintenance that is necessary
- Motor is tightly fastened to avoid vibration.
- Ensure Shaft is turning freely and bearings are correctly greased.
- Regular inspections such as cleanliness etc, casing fan.
- Ensure the motor is not overheating, so no hot spots.
- Regular on load testing.
- Balance Test
MORE
- Change Bearings and Seals
- Regular on Load Testing
- Clean Casing
- Clean and Check Fan
- Check Windings
- Check Terminal Box
- No Abnormal Noises
- No Vibrations
with reference to electrical motors
Describe the tests carried out to prove good electrical condition
Insulation Resistance Test
- Testing the quality of insulation between electrical conductors and earth or between conductors.
HOW
- Tested with an A Rated Megger.
STEP BY STEP
- Phase to Phase (probe to 1 conductor, other probe to other conductor)
- Phase to Earth (probe to conductor, other probe to ships hull)
- Minimum Acceptable Value is 1mega ohm.
Continuity Test
- Testing if the circuit has continuity, which means if electricity can pass through without interruption.
- They are done over all the phases.
HOW
- Tested with a multiimetre and checks weather the circuit is intact, no continuity = break or fault in the circuit.
STEP BY STEP
- Touch probes to both ends of the circuit.
- Beep/small resistance = continuity.
- No beep/infinite resistance = no continuity (open circuit).
Balance Test
- Resistance readings for each winding are taken, a good motor will show that the windings resistance readings should all be similar.
- Tested with a multimetre also.
with reference to the testing and maintenance of large electrical motors
State the minimum satisfactory value of insulation resistance
1 Mega Ohm
with reference to the testing and maintenance of large electrical motors
State instrument AND the voltage to be used for the insulation resistance test
- Megger Tester
- 500V for DC
- 440V for AC for a 440 System
with reference to the testing and maintenance of large electrical motors
State the regular maintenance that is necessary for good electric motor operation
- Motor is tightly fastened to avoid vibration.
- Ensure Shaft is turning freely and bearings are correctly greased.
- Regular inspections such as cleanliness etc, casing fan.
- Ensure the motor is not overheating, so no hot spots.
- Regular on load testing.
- Balance Test
ELECTRICAL TESTS - Continuity Test
- Insulation Resistance Test
with reference to electrical motors
List FOUR maintenance actions that are necessary for good operation
- Keep motor and surrounding area clean (good housekeeping)
- Bearings should be greased regularly
- Regular insulation resistance tests
- Motor must be secured tightly (avoid vibration and damage)
with reference to electrical motors
Describe how to test for electrical faults within an electrical motor
Insulation Resistance Test
- Testing the quality of insulation between electrical conductors and earth or between conductors.
HOW
- Tested with an A Rated Megger.
STEP BY STEP
- Phase to Phase (probe to 1 conductor, other probe to other conductor)
- Phase to Earth (probe to conductor, other probe to ships hull)
- Minimum Acceptable Value is 1mega ohm.
Continuity Test
- Testing if the circuit has continuity, which means if electricity can pass through without interruption.
- They are done over all the phases.
HOW
- Tested with a multiimetre and checks weather the circuit is intact, no continuity = break or fault in the circuit.
STEP BY STEP
- Touch probes to both ends of the circuit.
- Beep/small resistance = continuity.
- No beep/infinite resistance = no continuity (open circuit).
Balance Test
- Resistance readings for each winding are taken, a good motor will show that the windings resistance readings should all be similar.
- Tested with a multimetre also.
with reference to a small 3 phase electrical motor driving a transfer pump that is not used on a regular basis failing to rotate when the start button is pressed
Outline the procedure to determine the possible cause
Safety First
- Isolate the power supply and lock out/tag out the circuit
Mechanical Checks
- Pump Side - try rotating the pump shaft manually.
(if it does not rotate, check for seized gears, clogged impeller)
- Motor Side - try rotating the motor shaft manually.
(if stiff or jammed, suspect seized bearings or shaft misalignment)
Electrical Checks
- Power Supply - use a potential indicator or multimeter to confirm 3 phase supply at motor terminals.
- Motor Internals - Perform continuity test across motor windings.
no continuity = broken windings
low resistance between winding and earth = possible ground fault
- Use Megger to confirm insulation integrity.
with reference to a small 3 phase electrical motor driving a transfer pump that is not used on a regular basis failing to rotate when the start button is pressed
Explain the procedure to remove the motor should it be faulty and require changing
1), Switch off the motor and its attached pump.
2), Isolate the motor safely and lock out the power supply.
3), Place warning notices:
- On the starter panel
- In the control room to inform other crew members
4), Wear correct PPE and prepare necessary tools and lifting equipment.
5), Ensure adequate lighting in the work area.
6), Disconnect wiring from the terminal block on the motor casing.
7), Unbolt the motor from its mount.
8), Lift off the motor using appropriate lifting equipment.
9), Transfer the motor to a designated storage space or repair area.
with reference to the testing and maintenance of large electrical motors
State the minimum satisfactory value of insulation resistance
1 Mega Ohm
with reference to the testing and maintenance of large electrical motors
State instrument AND the voltage to be used for the insulation resistance test
- Megger Tester
- 500V for DC
- 440V for AC for a 440 System
with reference to the testing and maintenance of large electrical motors
State the regular maintenance that is necessary for good electric motor operation
- Motor is tightly fastened to avoid vibration.
- Ensure Shaft is turning freely and bearings are correctly greased.
- Regular inspections such as cleanliness etc, casing fan.
- Ensure the motor is not overheating, so no hot spots.
- Regular on load testing.
- Balance Test
ELECTRICAL TESTS - Continuity Test
- Insulation Resistance Test
