on video 3 Phase Electric Motor Troubleshooting Guide

 

In this video you learn about 3 phase motor circuit troubleshooting or how to find out fault in three phase induction motor circuit . How to test magnetic contactor, how to test a overload relay, how to test a 3 phase motor using ohm meter, how to test fuse using multi meter and how to test AC current (ampere) in 3 phase circuit using clamp meter 

It’s always important to identify the real cause of burned windings and not just to replace the electric motor. Motor windings have a different appearance in all these failure situations: single-phase burnout, overload, unbalanced voltage, and voltage spikes. Voltage spike damage occurs more often in motors controlled by variable frequency drives.

These problems are all caused by in-plant faults that require correction. A replacement motor can fail sometimes immediately if the in-plant problem isn’t corrected.

It’s very important to accurately identify problems that require a motor’s removal and replacement. Winding problems that are identified should be documented. A history of the plant’s motor problems (on computer software) will point out problem areas that ran be improved, or even eliminated.

A short is a common winding breakdown, and it requires rewinding or replacing the motor. Shorted turns are caused by nicked coil wire, high-voltage spikes, conductive contaminants, overheated winding, aged insulation, and loose, vibrating coil wires.

The most of the resistance to current flow in an AC motor is furnished by . The resistance of the wire in a complete phase is a very small percentage of the motor’s total impedance (resistance plus inductive reactance). Inductive reactance makes each turn very significant in the motor’s ampere demand. Each turn supplies much more inductive reactance than resistance.

 increases the amperes of the faulty phase, making it easy to identify the problem. Circulating current in the closed loop often melts the circuit open. When this happens, the circulating current and the turns within the closed loop are eliminated.

Only the resistance of the wire (turns) within the closed loop is now eliminated from the phase winding. Without the ampere demand of the circulating current, the difference lessens between the amperes of the faulty phase and those of the normal phases.

 is all that is needed to identify the faulty phase. Please note that the rotor should be turned during this test to eliminate its effect. Shorted turns in any AC winding are usually visible. They become charred quickly from the high circulating current that is transformed into them (Figure 2).

When a motor is ““, the winding is shorted either to the laminated core or to the motor’s frame. The problem is usually found in a slot, where the slot insulation has broken down. Water is the most common cause of a grounded winding. A solid ground requires rewinding or replacing the motor.

Some causes of slot insulation breakdowns are overheating, conducting contaminants, lightning, age, pressure of a tight coil fit,

A phase-to-phase short is caused by insulation breakdown at the coil ends or in the slots. This type of fault requires rewinding or replacing the motor. Voltage between phases can be very high. When a short occurs, a large amount of winding is bypassed. Both phase windings are usually melted open, so the problem is easily detected.

Figure 4 is the lap-winding type. The ends of the coils are nested within each other and have phase insulation between the poles. The coils usually share the slots with other poles. Insulation also separates the coils of each phase in the slots. Some motors 

Figure 5 is an . A phase-to-phase short occurs in the slot more often than at the coil ends. When a breakdown occurs in the slot, copper usually melts and fuses to the slot laminations.

This copper has to be ground out and removed before the motor is rewound, or it becomes a hot spot and deteriorates the new insulation.

Motor lead connecting lugs should be thick enough (throughout the connection) to represent the circular mil area (size) of the motor’s lead wire. If any part of the lug is too small, it becomes a resistor in series with the motor, and current will be restricted when the motor needs it the most – to start the load.

Figure 7 shows . Lug (a) is a piece of copper tubing, which has been partially flattened and has a hole

punched in it for the connecting bolt. Its ferrule will hold wire that has a much greater circular mil area than that of the bolted part of the lug.

The motor should be disassembled as soon as possible. If the motor has ball bearings, they should be replaced. If it has sleeve bearings, the oil wicking material will pit or rust the shaft area located in the bearing window. Replace the oil wick material immediately. If the motor has an oil reservoir and oil ring, the reservoir should be thoroughly cleaned. The windings should be first tested with an ohmmeter.

 

In this video you learn about 3 phase motor circuit troubleshooting or how to find out fault in three phase induction motor circuit . How to test magnetic contactor, how to test a overload relay, how to test a 3 phase motor using ohm meter, how to test fuse using multi meter and how to test AC current (ampere) in 3 phase circuit using clamp meter 

It’s always important to identify the real cause of burned windings and not just to replace the electric motor. Motor windings have a different appearance in all these failure situations: single-phase burnout, overload, unbalanced voltage, and voltage spikes. Voltage spike damage occurs more often in motors controlled by variable frequency drives.

These problems are all caused by in-plant faults that require correction. A replacement motor can fail sometimes immediately if the in-plant problem isn’t corrected.

It’s very important to accurately identify problems that require a motor’s removal and replacement. Winding problems that are identified should be documented. A history of the plant’s motor problems (on computer software) will point out problem areas that ran be improved, or even eliminated.

A short is a common winding breakdown, and it requires rewinding or replacing the motor. Shorted turns are caused by nicked coil wire, high-voltage spikes, conductive contaminants, overheated winding, aged insulation, and loose, vibrating coil wires.

The most of the resistance to current flow in an AC motor is furnished by . The resistance of the wire in a complete phase is a very small percentage of the motor’s total impedance (resistance plus inductive reactance). Inductive reactance makes each turn very significant in the motor’s ampere demand. Each turn supplies much more inductive reactance than resistance.

 increases the amperes of the faulty phase, making it easy to identify the problem. Circulating current in the closed loop often melts the circuit open. When this happens, the circulating current and the turns within the closed loop are eliminated.

Only the resistance of the wire (turns) within the closed loop is now eliminated from the phase winding. Without the ampere demand of the circulating current, the difference lessens between the amperes of the faulty phase and those of the normal phases.

 is all that is needed to identify the faulty phase. Please note that the rotor should be turned during this test to eliminate its effect. Shorted turns in any AC winding are usually visible. They become charred quickly from the high circulating current that is transformed into them (Figure 2).

When a motor is ““, the winding is shorted either to the laminated core or to the motor’s frame. The problem is usually found in a slot, where the slot insulation has broken down. Water is the most common cause of a grounded winding. A solid ground requires rewinding or replacing the motor.

Some causes of slot insulation breakdowns are overheating, conducting contaminants, lightning, age, pressure of a tight coil fit,

A phase-to-phase short is caused by insulation breakdown at the coil ends or in the slots. This type of fault requires rewinding or replacing the motor. Voltage between phases can be very high. When a short occurs, a large amount of winding is bypassed. Both phase windings are usually melted open, so the problem is easily detected.

Figure 4 is the lap-winding type. The ends of the coils are nested within each other and have phase insulation between the poles. The coils usually share the slots with other poles. Insulation also separates the coils of each phase in the slots. Some motors 

Figure 5 is an . A phase-to-phase short occurs in the slot more often than at the coil ends. When a breakdown occurs in the slot, copper usually melts and fuses to the slot laminations.

This copper has to be ground out and removed before the motor is rewound, or it becomes a hot spot and deteriorates the new insulation.

Motor lead connecting lugs should be thick enough (throughout the connection) to represent the circular mil area (size) of the motor’s lead wire. If any part of the lug is too small, it becomes a resistor in series with the motor, and current will be restricted when the motor needs it the most – to start the load.

Figure 7 shows . Lug (a) is a piece of copper tubing, which has been partially flattened and has a hole

punched in it for the connecting bolt. Its ferrule will hold wire that has a much greater circular mil area than that of the bolted part of the lug.

The motor should be disassembled as soon as possible. If the motor has ball bearings, they should be replaced. If it has sleeve bearings, the oil wicking material will pit or rust the shaft area located in the bearing window. Replace the oil wick material immediately. If the motor has an oil reservoir and oil ring, the reservoir should be thoroughly cleaned. The windings should be first tested with an ohmmeter.