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D-Time is the starting Delay Time taken by a Motor to reach its normal running current. Normally during starting the Motor draws much higher levels of current and the D-Time setting is to ensure that the EOCR does not trip the motor before this time has elapsed. This prevents nuisance trippings during the starting period. After the set D-Time has elapsed the EOCR monitors the normal currents.
O-Time is the operating time in the event of over-loading. When motor currents exceed the desired set current value, the EOCR detects the increase in current and trips the motor within the set O-Time Long periods of Overloading result in the weakening of the Winding Insulation and later lead to motor failures.
The Alert/Prewarning is possible in some models. The Alert signal is through an additional Relay Output which is connected to a Buzzer, Hooter or Flasher and can be adjusted between 50% to 100% of the set current value. When the motor current exceeds the set Alert %age the AL-Relay is energised to obtain the prewarning signal.
Depending upon the type of motor and application, both types of protections can be useful. In cases where motors can withstand excessive periods of overloading or in case the tripping of the motor is considered a costlier affair then failure, the definite type of protection is preferred. For example, Traction Motors, Compressor Motors and Motors with special constructions etc. But in cases where overloading results in failure of other Mechanical equipment linked to the motor the definite type of protection is the ideal choice. For example - Conveyor Motor, Motors on SPM and other machines, Automation etc.
During Starting, sometimes the Rotor of the motor gets Locked or Jammed which could be as a result of Bearings or Bushes or Excessive Loads, the current at that point can be 3-10 times of the Full Load rating of the motor. When motor currents exceed 3 times of the set current value, the EOCR detects it as Locking of Rotor and trips the motor, thus preventing it from premature failures.
When any of the 3 Phases L1, L2 or L3 is lost in the system, the condition is termed as Single Phasing or Loss of Phase. The EOCR operates on current sensing principle and has in built Current Transformers (2 or 3) which immediately detect loss of any Phase and trips the motor. Other relays which operate on Voltage Sensing Principle are not so accurate and therefore less reliable. Also extended periods of motor running without any one Phase leads to total failure.
The EOCR with Phase Unbalance protection is designed to detect a Phase Unbalance of 50% or more between any 2 phases. Any Unbalance below 50% does not cause the EOCR to trip. Thereby no nuisance trippings occur and the motor is also protected during such conditions.
The EOCR with Phase Reversal protection has provision for bypassing the Phase Reversal trip with DIP switch settings on the face of the EOCR.
The EOCR 3DM series has been designed to assist its users to improve their productivity. The EOCR 3DM series has in built Timer to record Total Running Hours of the motor which assist in preventive maintenance of the Motor. The maximum Total Run Hour is 99,999 Hours and is not adjustable.
