Overload (for both cyclic and sustained overload conditions)
Single phasing / unbalance
Undercurrent / load loss
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.
Should the motor load exceed the thermal capacity allowed by the thermal IDMT curve (Class 15 cold and Class
5 hot curve) the motor overload LED indicator will be illuminated, the relay healthy indicator switched off and
the main trip relay de-energised to stop the motor.
The same motor overload LED can be used to read the actual load current being drawn by the motor during
normal running conditions. This is achieved by pressing and holding the control panel mounted reset
pushbutton, while 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.
In the event of a motor 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 and 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.
298 Soutter Street, Pretoria West
Postnet Suite #73, Private Bag X06, Quagga, 0058
Tel: (012) 327-1729 Fax: (012) 327-1733
E-mail: [email protected] Http://www.newelec.co.za
KB LV Motor Protection Relay
INSTALLATION AND SETTING UP PROCEDURE
Example 1:
Protection for 3 kW 380 Volt three-phase motor
Motor full load 6,5 Amp
Suggestion:
KB10 / 380V
Example 2:
Protection for 132 kW 525 Volt four-pole, three-phase motor
Motor Full Load 175 Amp
KB200/525/200:5
Ordering examples for the various models
Interposing secondary
Model or relay type
Current setting range current transformer
ratio where required
KB 1
0,1
to 1 Amp
Not required
KB 5
0,5
to 5 Amp
Not required
KB 10
1
to 10 Amp
Not required
KB 25
2,5
to 25 Amp
Not required
KB 50
5
to 50 Amp
50:5 Class 1 2,5 VA
KB 100
10
to 100 Amp 100:5 Class 1 2,5 VA
KB 200
25 to 200 Amp 200:5 Class 1 2,5 VA
1. Protection Features
2. Description of Operation
10. Ordering Information
