what is eocr
TRANSCRIPT
What is EOCR ?
1. Preface
Traditionally, TORs have being used for motors for a long time. But developing of the electronics
technology tends for people to apply its technology to every industrial field with its accurcy and
flexibility. According to this trends, EOCR came out to electric industry field. EOCR has three main
parts which are the sensor part detecting current, the process part caculating and deciding the
sensing value, and the output part resulted from the processing. The accuracy and flexibility of
electronics let them protect not only motors but also mechanical loads connected to the motors.
The mechanical load and the current of motor are in indispensible relation. There is one important
principle in this, That is, we can surmise the status of mechanical load and a motor from monitoring
the current of the motors. If the mechanical load increases, the current of motor also get to
increase. The abnormal increase of mechanical load tells us some problems are happening in
there and results in a burned motor and broken machine. We can diagnose and protect the motor
system by checking the current of motors with eletronic technology. Usually when we design the
machines using a motor, we set the rating of the motor higher than the one of machine in
cosideration of safety, reserve and economy. So both ratings of the motor and machnine are not
same. While we sets the current value at the rating current of motors in TOR, but we sets the
current value at the rating of machine load by using the ammeter function in EOCR. By this, we
are able to diagnose the status of the mecanical load and motors. For example , let ’s assume that
there is a pump hindered by unexpected foreign material. then the current of motor comes to
increase and means some problems are happening in there. If the current of motor does not
increase over the rating of the motor, the TOR will not be tripped. As a result, this overload of the
pump can proceed to bigger problem. But EOCR will be tripped instantly as to the actual set
current value not to proceed to bigger problem.
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Mechanical Load
( 100 % )
Increase
Decrease
Current ofMotor
( 80% or so)
Increase
Decrease
Detecting current with CT sensor
Diagnosing the condition of
machine and motor
Diagram 1-1 . Flow of EOCR
Reducing the down time of
systems
2. Principle
The basic principle of protecting with EOCR is very simple. The two elements we have chosen for
this are the current and the operating time. These two elements make diverse applications in
industrial field. The user using EOCR just set the suitable values of current and time after
confirming the real current of motor through using the ammeter function itself. The user just intrrupt
the power in a time expected when the current of motor overflows in motor than the user wants it.
We can think a new principle about the time expected . That is definite time, which has very simple
characteristic curve.
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Diagram 1-2 . Structure of EOCR
Picture2-1. Inverse time characteristic Curve
Picture2-2. Definite time characteristic Curve
0.2
Motor
Contactor
A
Processor
EOCR
Output
Sensor part
At the picture above, EOCR uses definite curve of the picture2-2, whereas traditional TOR uses
Inverse curve of the picture2-1. Inverse charateristic has a reciprocal propotion curve between
current value and trip time, in which is impossible for user to set the some values. But definite
charateristic shows us that EOCR trips instantly after detecting of being over the time and current
value preset by user. Here in the definite time charateristic curve, we can see that trip time has a
quick response charateristic of 0.2sec (Ground fault , Short circuit :0.05sec). This is the merit of
electronic tech itself only and makes it possible to have the shear pin function in machine. The
flexible setting of current and trip time by user makes various applications. From now we will look
over below applications.
3. Applications upon the loads.
1) Fan, Blower
The designers select the TOR fit at the rating current of motor for their motors normally. But the fan
or blower uses only the 75~85% normal power of the rating power of motor, If the machine is
overloaded 2times by some reasons, the current will be about 1.5~1.7times of the rating current of
the motor. This means that some troubles are happening in it and we have to stop the machine and
check the system to protect it from the proceeding further problem. However, there is a enough
possibility that TOR(10 class) isn’t able to trip even untill about 4 minutes following the table 3-1
and it can be resulted in broken machine and burned motor.
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Trip class
10A
10
20
30 9 Tp ≤ 30<
Tripping time Tp(sec) at 7.2 times
2 Tp ≤ 10<
4 Tp ≤ 10<
6 Tp ≤ 20<
A B C D
Thermal typecompensated forair temp variations
1.05 1.2 1.5 7.2
10A : 2min
10 : 4min
20 : 8min
30 :12min
Limits of operationof time- delay
Over2h
Under2h
+20 ℃
Type ofoverload relay
Multiple of current setting Referenceambient airtemperature
Table 3-1. IEC 947-4-1 for relay
However, EOCR can detect the real running current and trips the relay when the current exceed
the preset value of 1.1~1.2times in preset time that the user wants through sensing the abnormal
state of mechanical load by monitoring the current change caused by a bearing and fan blades
trouble like and can stop the motor instantly and can check it for troubles not to spread over.
Moreover, in cases of the cut belt (Idle Running), the loosened belt and the blocked filter caused by
using it for long time , it turns to the current decreasing. By monitoring on that current notify us its
fault state and the time for filter to be changed. Low current monitoring can be a good application
by use of under current protection relay function.
2) Pump system
There may be an overload and underload in pumps. If the foreign material ,specially in sewage
pump, hinder the rotation of the pump blade, the current will increase in pump and incur failed
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Picture 3-1. Blower with machine and filter trouble.
Picture 3-2. Blower with loosened belt Picture 3-3. Blower with cut belt
pump and burned motor. EOCR can check sensitively the change of current and diagnose the
mechanical state of pump whether it is normal or not. EOCR has a shear pin function to protect
pump system from stalled(jamed) state in 0.2sec of quick response. EOCR is able to notice it , if
valve or filter is blocked by monitoring undercurrent.
In submersible pump, You can protect a submersible pump having cooling effect of water from the
Dry running caused by the failed level switch . In this case has EOCR the undercurrent in motor.
EOCR can protect the system from the undercurrent as a double protection method. If the filter of
pump is blocked, the undercurret will show, then you can be informed when the filter needs to be
changed adequitely. Like pumps using the water, there is always danger to get electric shock or
ground fault . This can be protected by EOCR using the ZCT from spreading fault.
(EGR, EOCR-xxZ)
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Picture 3-4. Pump
Discharge
LevelSwitch
Power supply
M
Picture 3-5. Sump Pump (Submersible Pump)
3) Crane , Hoist
Each Hoist and Crane has its own durable weight(load). EOCR can recognize whether the weigt is
exceeded or not, to prevent a accident may be catastrophe with instant and precise response
charateristic previously. When the weight gets to be heavy, the burden to the motor increases and
the current of motor gets to increase. If the load exceeds the rating weight of machine, it should be
stoped and restarted after lightening the load for safe and machine. However, TOR may not be
tripped for 2hours in state of 1.2 times rating current.
4) Belt Conveyer (fluctuating load)
Mechanical impact could make the designer choose the high class TOR due to thermal memory to
prevent annoying stopping. But this could make TOR hard to operate precisely because of the long
trip delay time. EOCR can monitor the state of load ,like as congested goods to convey and cut
belt ( dry running ) caused some reason, and diagnose it with current magnitude and prevent a
further spreading accident in advance.
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Picture 3-6. Crane Picture 3-7. Hoist
Conveyor
Mechanical impact !
MConveyor
5) Machine tools
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Picture 3-8. Conveyer
Motor
EOCRLT47LR97D
TORLRD
Threshold (preset)
I=0
Is=Ir
Overload
D-time Fluctuating load
Thermal memory
O-time
Start / Motor
ON
Output contact
Power Supply: A1,A2
Output contact Unwanted motor stopping
9596
98
95 96
TORIn case of above application, you cannot set Ir value as normal operation due to thermal effect. So you will have to set the value higher than normal. But in this case, TOR can not perfectly protect the motor when there is overload. Some trouble can happen to the mechanism if you are using an oversized motor .
EOCREOCR can protect well because it doesn’t have thermal memory. If overloaded , it should be tripped in preset time ( O-time).EOCR doesn’t care about oversized motor because it can be set at actual current of load by red LED and so you may not give any damage on the mechanism.
Picture 3-9. comparison between TOR and EOCR
Innumerable machine tools are used in machine industy. Kinds of drills, bites, saws, and grinders
etc., are used in machine tools as a cutting parts. CNC machine is also same as normal machine
tools. All kind of machines use a motor for processing . Here, EOCR could know the state of
machine like as overload, jam and so on and this can be done by monitoring the current of its
motor.
For example, EOCR is able to check the sharpness of drill in drilling machine. If the point of drill get
to be dull, the friction between the drill and object would get to be big and the current of motor get
rising due to increasing friction power. This dull point of drill could give an inefficient productivity.
EOCR helps you to reduce the producing defective goods.
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Picture 3-10. Drilling machine tool
Picture 3-11. CNC machine tool
Drill
Object
Picture 3-12. Example in drilling machine
6) Chemical processing motor.
This will be one example EOCR can do for chemical processing with the auto/instant reset
function of EOCR. If the machine, like an extruder, an agitator and a pump treats the liquid
materials can be hardened, stops its operating by cause of overload even the mtor has ability can
operate with its oversizing, you would need your system to be restarted prior to getting the material
hard. But TOR can not restart your system instantly before the bimetal is cooled. EOCR can restart
your system any time. Recovering the machine jamed with hardened material is time cousuming
job. You can reduce this time loss.
Another example needs constant temperature in chemical processing. They use electric heater for
heating . If the one of heating line in heater is cut by cause of long time using or some reason,
temperature will decrease and it is followed by low current. EOCR can check this low current
condition and protect this by use of EUCR. Keeping stable temperature is important issue in
chemical industry.
4. Applications upon mechanism
1) Jam Protection ( Shock relay )
When mechanical jam happens because of unexpected material in the pump mechanism or belt
conveyor ( belt, gear, etc), the motor has a peak current at the moment. The LT47 can detect if the
current is over than the set value for a preset time and it is able to break the power.
( you should set at minimum value of O-time 0.2sec).The contact of LT47 can be used for an alarm
or the breaking power by giving a signal to the coil of contactor or the shunt trip coil of circuit
breaker.
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A
Picture 3-13. Example of Heater fault
▪ Application Object ; Extruder , Belt Conveyer , Parking machine , Machine tools
Crusher, Pump , Fan
10
M
LT47
TOR
ALARM
JAM !
Trip Command
or
or
KM1
M
EOCRLR97
LT47
JAM !
or
Trip Command
or
ALARM
KM1
How to make a setting value as a shock relay
Crusher Motor 11 kW , at 380V 22A
TOR LRD22 set at 24A
Shock relay LT47 set at 40A ~ 60A D-time setting : 4sec O-time setting : 0.2 sec (setting value depends on your need)
How to make a setting value as a shock relay
Heavy duty belt conveyer Motor 2.2kW, at 380V 5A
EOCR LR97D set at 5.5 A D-time setting : 6sec O-time setting : 5sec Shock relay LT47 set at 10A ~ 15A D-time setting : 7sec O-time setting : 0.2 sec (setting value depends on your need)
Picture 4-1. an example of application.
2) High mechanical inertia of load (long starting time)
In case of high inertia load , we get to choose a high class TOR due to long starting time. A high
class TOR has also long tripping time. If the overcurrent flows to the motor, it may make the life of
motor short or get to burn the motor because of long tripping time. But you can set the value of the
starting time and the tripping time respectively in EOCR and give a delay to the starting. If it is
overloaded in motor, you can trip the relay in preset tripping time wanted to protect its system
quickly and precisely .
▪ Typical application ; FAN , Blowers, Centrifugal machine
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t
Ir I
Class 30
Class 20
Class 10
Typical motor starting curve with high inertiaTypical inverse curves of TOR t
Ir I
Definite
curve
D-time
setting
Adjustable
Definite
curve
O-time
setting
Adjustable
Picture 4-2. Typical TOR (LRD, LR3D)
Typical motor starting curve with high inertiaTypical inverse curves of TOR
Picture 4-3. EOCR (LR97D, LT47)
You should use class 30 TOR due to long starting time. If there is overload after starting time. The tripping time is longer than class 10 TOR , it could cause motor to overheat and burning.
EX) Blower /40HP starting time : 15-18sec TOR Class 20 Time delay Not adjustable Blower /10HP starting time : 10-12sec TOR Class 20 Time delay Not adjustable Water pump /40HP starting time : 4sec TOR Class 10 Time delay Not adjustable
According to motor specification, we can easily set the value of Ir and starting time and tripping time within setting range. The motor starting time is depending on the load. EOCR can be easily adjusted at practical starting time by D-time setting
EX) Blower /40HP starting time : 15-18sec EOCR D-time setting : 18sec O-time setting : 7sec Blower /10HP starting time : 10-12sec EOCR D-time setting : 12sec O-time setting : 6sec Water pump /40HP starting time : 4sec EOCR D-time setting : 5sec O-time setting :5sec
3) Operating cycle more than 30 to 50 cycles/hour ( frequent stop-starting )
▪ Typical application ; Hoist , Crane, Short length belt conveyer, CNC machine tools
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t
Ir I
Class10
Typical Motor starting curve
Thermalmemorydue to
frequentstarting of
motor
t
Ir I
Definite curveD-time setting
Adjustale from
0.5sec-30sec
Definite curveO-time setting
Adjustale from
0.2sec-10sec
Typical Motor starting curve
Definite curve of EOCR
Motor
EOCRLT47LR97D
TORLRD
Threshold (preset)
I=0
Overload
D-time
Frequent motor starting
Thermal memory
O-time
Start / Motor
ON
Output contact
Power Supply: A1,A2
Output contact Unwanted motor stopping
9596
98
95 96
Is=Ir
Picture 4-4. Typical TOR (LRD, LR3D) Picture 4-5. EOCR (LR97D, LT47)
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TORIn this kind of application, you cannot set the value of TOR as normal operation due to thermal effect ,so you should set higher value.TOR could not perfectly protect the motor if the system is overloaded
EOCREOCR can protect well because it doesn’t have thermal memory. If overloaded , it should be tripped in preset time ( O-time).
Picture 4-6. Frequent stop-starting chart