Motor Protection

Motor protection prevents damage to an electrical motor by reducing the incidence of problems, including internal faults and abnormal conditions. It is crucial to protect the circuits against overloads and fault currents. The size of the motor and the required voltage level will determine the type of motor protection. In addition, any untended motor should be protected against over and under-voltage, over-temperature, and fault currents.

Motor Protection Functions:

There are several protection features for motor protection schemes to consider:

• Motor protection devices are ideal for protecting against various types of damage that can occur within a motor, including faults arising from excess torque or vibration. 
• Motor protection units also overcome other mechanical limitations, such as:
• Startup frequency management
• Control operating features like the voltage, phases, and short-circuit.
• They also overcome the limitations, including:
• Rating and type of motor horsepower 
• Nature of the process
• Motor environment and the associated switching device
• Hot/Cold permissible locked-rotor time, permissible accelerating time.
• Time versus current curve (when starting the motor).

Motor Protection Devices:

Circuit protection is carried out through devices for timely disconnection of electric motors from the network in alterations to the regular work regime. This is crucial for preventing motor insulation, windings, and electrical connection deterioration. The most used devices include:

Fuses:

The fuse is the simplest form of circuit protection, consisting of a fuse element designed to prevent or melt further current flow. Fuse is highly recommended in transformers and backup protection for other protective devices. For instance, in motors, a double element fuse is ideal for providing a range of protection, including an overload range. Time delay fuses are the most valuable fuses for motor branch circuit applications. This fuse can be sized closer to the motor's full-load current, providing a degree of overload protection, better short circuit protection, and the possible use of a more miniature disconnect switch.

Circuit Breakers:

A circuit breaker is a simple electromechanical device for an individual Electric Motor that provides protection against overload, changes in input current, or unintended interruptions to the primary circuit. The correct type of circuit breaker should be used for electric motor protection. 

Overload relays:

Overload relays avoid excessive heat from the overcurrent condition and protect the motor, motor branch circuit, and other components. These relays are part of the motor starter that protects the motor by monitoring the current flow in the circuit.

Typical applications of motor protection:

Motor protection is ideal for managing and protecting synchronous and asynchronous motors. They are also suitable for 

• circuit breakers  
• motors in a variety of drive applications, such as:
• motor drives for pumps 
• fans 
• compressors 
• mills
• crushers.

Benefits and Features:

• They prevent damage to electrical motors.
• Protect the grid from spreading disturbances.
• The application-specific standard configuration reduces the time needed to set up and commission relays.
• They also provide pre-configured systems for industrial and utility distribution applications.