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Newelec KA Motor Protection Relay

The Newelec KA relay is an economically priced low voltage motor, protection relay. The integral current transformers allow for direct connection into the main circuit of the protected motor for currents up to 25 amps. Above 25 amps external current transformers are used. The relay offers the following protection:
Overload Cyclic and sustained overload with pre loading, thermal memory, hot and cold curve
Unbalance/Single Phasing Motor load currents unbalanced > 30% on starting, running or light loads.
Phase Rotation Prevents motor operation with incorrect supply voltage phase sequence.
Phase Symmetry Prevents motor operation with supply voltage phase unbalance > 5%.
Overvoltage Prevents motor operation when main circuit voltage is > 1 15% of rated supply.
Undervoltage  Prevents motor operation when main circuit supply voltage is < 90% of rated supply.
Minimum Load Minimum load trip level adjustable from 10% to 100% motor Ifl with a 25 second trip delay.

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The relay overcurrent level dial setting covers 10% to 100% of the specified current transformer. Models covering the current ranges 1 to 10 amps and 2,5 to 25 amps are direct connected. The ranges 5 to 50, 10 to 100 and 20 to 200 amps utilise external current transformers.The overcurrent level setting is calibrated in amps on the relay faceplate to avoid confusing scale factors.

Overload Protection is provided against cyclic and sustained overloads. Pre-loading with thermal memory, utilising accurate hot and cold thermal curve characteristics to IEC 255-8 provides this protection. The thermal IDMT curve is class 15 cold and class 5 hot. This curve will provide adequate protection in the event of a motor stall, both during starting and running conditions.

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Thermal Lock-out Period
In the event of an overload trip, the entire thermal capacity of the motor has been utilised. If auto reset has been selected, the motor overload LED will flash at a one-second rate, until the thermal capacity has integrated to 33%. At this point the overload LED will switch off. The relay healthy LED will switch on to indicate that the motor can be returned to service. The relay will reset to a class 5 hot Curve.

If manual reset is selected the motor overload LED will remain on until the control panel mounted reset button is pressed. If the thermal capacity has not integrated to 33% then the auto reset sequence is initiated. If the thermal capacity has integrated to > 33% then the overload LED will switch off. The relay healthy LED will switch on to indicate that the motor can be returned to service.
 

Unbalance / Single phasing

Phase unbalance protection is provided independent of motor load. In the event of the three line currents becoming unbalanced by more than 30% a 5 second trip delay is initiated.
 

Phase Rotation

Incorrect phase rotation will result in the phase rotation LED switching on. The relay healthy LED will then switch off and de-energise the main trip relay. This will prevent motor operation with incorrect phase sequence and resultant damage to driven equipment. Once the phase rotation has been corrected the phase rotation LED will switch off and re-energise the main trip relay. The relay healthy LED will then switch on to indicate that the motor can be returned to service.
 

Phase Symmetry

In the event of the phase voltages becoming unbalanced by more than 10% a 2 second trip delay is initiated after which the phase rotation LED is pulsed at a one second interval. The relay healthy LED will then switch off and trip the main relay. If the unbalance level reduces to below 10% then the flashing phase rotation LED will switch off and re-energise the main trip relay. The relay healthy LED will then switch on to indicate that the motor can be returned to service.
 

Overvoltage

In the event of the main circuit voltage becoming greater than 115 % of rated supply a two second trip delay is initiated. After this the phase rotation LED is pulsed at a 75% duty for a 4 second period. The relay healthy LED will then switch off and de-energise the main trip relay. If the main circuit voltage level reduces to below 115% then the flashing phase rotation LED will switch off and re-energise the main trip relay. The relay healthy LED will then switch on to indicate that the motor can be returned to service.
 

Undervoltage

In the event of the main circuit voltage becoming less than 90% of rated supply a two-second trip delay is initiated. After this the phase rotation LED is pulsed at a 25% duty for a 4 second period. The relay healthy LED will then switch off and de-energise the main trip relay. If the main circuit voltage level increases to above 90% then the flashing phase rotation LED will switch off and re-energise the main trip relay. Tile relay healthy LED will then switch on to indicate that the motor can be returned to service.
 

Under current Protection

The minimum load current level adjustment range is 10% to 100% of the rnax load current dial setting. If the load current drops below the set value but is > 10% of motor Ifl a 25 second trip delay is initiated. If the load current does not increase above the under current level adjustment or drop below 10% of motor full load current setting within 25 seconds the motor will be tripped on undercurrent.

Should the load current increase above the under current level setting the under current trip timer is reset and will start a fresh trip timing cycle on the next undercurrent condition. The undercurrent condition must persist for an uninterrupted 25 second period to effect an undercurrent trip. Any recovery within the 25 second period will result in the re initialisation of a new 25 second trip period.

 

LED Indication

Red LED trip indicators with clear descriptive fault conditions have been mounted oil the control panel to assist maintenance personnel in determining the exact cause of a trip.
 

Motor Overload

This indicator will be illuminated and the main trip relay operated if the motor load has exceeded the thermal capacity allowed by the thermal IDMT curve (class 15 cold and class 5 hot curve). Should the control panel mounted reset pushbutton be pressed in this state, or if the auto manual reset slide switch is set to auto, the motor overload LED will start to flash at a 50% duty for a 1 second period until the thermal capacity value recovers to 33%. At this point the main trip relay will re-energise and the relay healthy LED will switch on to indicate that that the motor can he returned to service. An additional function of the motor overload LED for maintenance or commissioning personnel is the ability to read the actual load cur-rent being drawn by the motor. This is achieved by holding the reset push button and trimming back the maximum load current dial until the motor overload LED switches on. The calibration on the max load current dial at which this occurs is the actual load current being drawn by the motor.
 

Phase Unbalance

This indicator will be illuminated when the three line currents drawn by the motor become unbalanced by more than 30% after which a 5 second trip delay is initiated.
 

Min Load Trip

The min load indicator will switch on and the main trip relay will de-energise 25 seconds after a min load condition when the motor load current drops below the min load % MLC dial setting, but is >10% of the max load current dial value and remains in this state for the full 25 second period. If during this 25 second period the load current increases above min load % MLC dial setting and then drops below this value once more a new 25 sec trip delay period is initiated.
 

Phase Rotation

This indicator is used to indicate various Supply voltage related problems as follows:

Fault

Indication pattern

Incorrect Phase Rotation LED switches on and stays on. Remove supply, correct and restore to reset.
Unbalanced voltage LED switches on and off at 1sec rate. Resets when supply unbalance <10%
Supply Overvoltage LED switches on 3 sec off for 1 sec. Resets when supply voltage <115%Vs
Supply Undervoltage LED switches on 1 sec off for 3 sec. Resets when supply voltage >90%Vs
 

Relay Healthy

This is a green LED and is used to indicate that no fault conditions are present, all relay self test diagnostic programs indicate healthy, and that the relay is ready for service.

NEWELEC KA SPECIFICATIONS

Primary Measurement range

Model Setting Range Max Reading CT Ratio (External)
KA 10 1 to 10 amps 50 amps Direct
KA 25 2,5 to 25 amps 250 amps Direct
KA 50 5 to 50 amps 500 amps 50 to 5
KA 100 10 to 100 amps 500 amps 100 to 5
KA 200 20 to 200 amps 2000 amps 200 to 5

 

Input Converter (Internal) Maximum Load Current Sensor
Current Transformer Ratio 1 000: 1 Level Setting Accuracy +/- 4%
CT Secondary 1 amp Linearity   +/-  4%
Class Class 1 Repeatability +/-  1%
Rating 0.1 va Detection Level +/- 1%
Frequency Response 40 - 66 Hz Calibration arnps

 

Model Min Max
KA 10 1 10
KA 25 2,5 25
KA 50 5 50
KA 100 10 100
KA 200 20 200


Unbalance/Single Phasing Sensor
    Maximum Level Setting          > 30% I.e. (motor full load)
    Trip Delay                             5 seconds

Overload Trip Delay Curves
    COLD
    Ttrip = 15 (35,49 x heat^ln (I/Ie)^ 2  /  (I/Ie)^2 - 1)

    HOT
    Ttrip =  5 (35,49  x heat^ln(I/Ie)^2  /  (I/Ie)^2 - 1)
    Accuracy    + 5%
        1,2 I.e. to 10 I.e.
        + 10%
        1,01 I.e. to 1,2 I.e.

Overload Thermal Lock-out Time to recover 33 % Capacity
Treset  =  Curve [2,33 (35,49 x 2) 15 log (100 / 70)] - Motor running

Treset =  Curve [2,33 (35,49 x 4) 15 log (100 / 70)] - Motor standstill

Main Trip Relay
    Current Rating    5 amps 22OV ae
    Configuration    1 n/o + In/c
    Terminals    n/o 7&8
                       n/c 9 & 10

Environmental Specifications
Reference Standards IEC 255
Isolation N/O Open Contact    1 kV 1 min IEC 255-5 C
Isolation Separate Contacts   2 kV 1 rain IEC 255-5 C
Impulse Withstand  5 kV IEC 255-4 E 111
High Frequency   IEC 255-4 C 111



Fault indication
Operation                Latch on Trip

Resetting Fault Indication Latch
Overload Trip
    1.    Auto if selected on control panel
    2.    Manual by control panel push button  
    3.    Interrupting aux. supply once thermal capacity has been restored

Unbalance    or Single phasing
    1.    Manual by control panel push button
    2.    Interrupting aux. supply

Control Supply
110V - 220 vac Terminal block selectable
Range 90% to 5% of selected range

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Wiring diagram. Panel installation
by Woodrow Engineering, (Kimberley)cc.
woodkims.gif (1224 bytes)   Woodrow Engineering Sales (Kimberley, South Africa)cc.
Tel. +27 (0)53 8312 094, Fax +27 (0)53 8312 094 - e-mail: jazz@woodrow.co.za