Diligent Micro Controls manufactures Protection Relays for AC Applications. Diligent Micro Controls offers Electronic Controllers, Electronic Control Systems & Electronic Control Relays for specific industrial applications. The Protection Relays for AC Applications are available for Over Load [OL], Single Phasing [SP], Phase Reversal [PR], etc. The overload relays are available in 1ph and 3ph types. 1ph-relays are useful on single phase load and can also be used as economical solution for 3 ph applications whenever load is balanced. These are classified depending on the response to the overload condition and the classification is as follows:
Instantaneous type is primarily made for AC loads other then motors such as transformer, heater, etc. However, it can also be used along with other logic to control motor.
Time-Delayed overload relay find a wide usage. The tie delay provided in the relay avoids nuisance tripping in response to transient overloads but switches off the load if overload persists beyond the specified time.
Jam type overload relay is quite unique and offers reliable protection of loads such as Blower, Fans, Stirrer motors which are rather difficult to achieve with conventional thermal relay. Jam relay not only saves the motor, but restricts the possible damage to the equipment & loss of production by advance intimation before catastrophic failure takes place.
Single Phasing [SP] protection in these Protection Relays for AC Applications is either Current Operated Single Phasing [COSP] or Voltage Operated Single Phasing [VOSP]. COSP is realized by sensing each of the phase current continuously. As soon as current in any one phase is lost, control relay changes the state. This greatly limits the heavy thermal stresses due to large current flowing in the connected phase-windings of motor. VOSP protection monitors all 3 supply phases and acts when one of the phases of 3 phase supply is missing. COSP is effective even when the phase is lost while the motor is in operation.
