BASICS FOR ELECTRIC MOTORS PROTECTION
Overview on the importance of electric motor protection.
Electrical
a. Power surges, voltage drops, unbalance and phase losses causing variations in the absorbed current.
b. Short circuits where the current can reach levels that can destroy the receiver.
Mechanical
a. Rotor stalling, momentary or prolonged overloads increasing the current absorbed by the motor and dangerously heating its windings.
The cost of these incidents can be high.
a. It includes production loss
b. Loss of raw materials,
c. Repair of the production equipment,
d. Non-quality production and delivery delays.
The economic necessity for businesses to be more competitive implies reducing the costs of discontinuous output and non-quality. These incidents can also have a serious impact on the safety of people in direct or indirect contact with the motor.
Protection is necessary to overcome these incidents, or at least mitigate their impact and prevent them from causing damage to equipment and disturbing the power supply. It isolates the equipment from the mains power by means of a breaking device which detects and measures electrical variations (voltage, current, etc.).
Every starter motor unit should include
1. Protection against short circuits, to detect and break abnormal currents – usually 10 times greater than the rated current (RC) – as fast as possible.
2. Protection against overloads to detect current increase up to about 10 RC and open the power circuit before the motor heats up, damaging the insulation.
These protections are ensured by special devices such as fuses, circuit breakers and overload relays or by integral devices with a range of protections.
Ground fault protection, which covers personal protection and fire safety, is not dealt with here because it is normally part of the electrical distribution in equipment, workshops or entire buildings.
Overview on the importance of electric motor protection.
Every electric motor has operating limits. Overshooting these limits will eventually destroy it and the systems it drives, the immediate effect being operating shutdown and losses. This type of receiver, which transforms electrical energy into mechanical energy, can be the seat of electrical or mechanical incidents.
Electrical
a. Power surges, voltage drops, unbalance and phase losses causing variations in the absorbed current.
b. Short circuits where the current can reach levels that can destroy the receiver.
Mechanical
a. Rotor stalling, momentary or prolonged overloads increasing the current absorbed by the motor and dangerously heating its windings.
The cost of these incidents can be high.
a. It includes production loss
b. Loss of raw materials,
c. Repair of the production equipment,
d. Non-quality production and delivery delays.
The economic necessity for businesses to be more competitive implies reducing the costs of discontinuous output and non-quality. These incidents can also have a serious impact on the safety of people in direct or indirect contact with the motor.
Protection is necessary to overcome these incidents, or at least mitigate their impact and prevent them from causing damage to equipment and disturbing the power supply. It isolates the equipment from the mains power by means of a breaking device which detects and measures electrical variations (voltage, current, etc.).
Every starter motor unit should include
1. Protection against short circuits, to detect and break abnormal currents – usually 10 times greater than the rated current (RC) – as fast as possible.
2. Protection against overloads to detect current increase up to about 10 RC and open the power circuit before the motor heats up, damaging the insulation.
These protections are ensured by special devices such as fuses, circuit breakers and overload relays or by integral devices with a range of protections.
Ground fault protection, which covers personal protection and fire safety, is not dealt with here because it is normally part of the electrical distribution in equipment, workshops or entire buildings.
source: 2010 IIEE Technical Manual
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