Motor Protection

All motors must have protection against 2 things as a minimum:

1. Short Circuit, for example fuses or a circuit breaker
2. Thermal Overload, for example an Over Load Relay (OLR).

Beyond that, you need to determine for yourself what else is important enough to you to spend the extra money on for protection. For example, many pumps in particular can be severely damaged by running in reverse, so a Phase Reversal Relay would be required. Others cannot tolerate low or high voltage conditions and require power monitoring relays as well. Many other types of pumps, such as sumbersibles, use the fluid as a lubricant so they must have low-level cutoff protection to avoid running dry. Others must be shut off long before then if there is a possibility of sucking air because they may not be self priming. Still others may have oil bath chambers and need seal-leak detection. Still others require temperature detection using thermistors or other probes in the motor and/or pump.

All of these types of protection have specialized relays designed to provide them. Some solid state protection relays can provide most, if not all, of them.

dear ashita

theraml over current ,under voltage ,and earth fault protection is required for up to 100 HP motors.

suresh kumar paliwal

In addition to the above, the Ingress Protection rating.

Use 20% up rated current MCB!