| What
is D-Time? |
| 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. |
| What
is O-Time? |
| 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. |
| Is
it possible to get an Alarm before the motor trips? |
| 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. |
| What
is better-Inverse or Definite type of protection? |
| 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. |
| What
is the meaning of Locked Rotor? |
|
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.
|
| How
a condition of Single Phasing or Phase Loss is protected? |
| 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 losss 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. |
| What
is meant by Phase Unbalance Protection? |
| 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. |
| What
if the motor has to run in both directions and Phase
Reversal protection is not required? |
| The
EOCR with Phase Reversal protection has provision
for bypassing the Phase Reversal trip with DIP switch
settings on the face of the EOCR. |
| Is
a Log Book required to monitor Total Running Hours
of the Motor when using 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. |
|
