COLD CURVE
CLASS 15
COLD CURVE
CLASS 5
In a similar fashion, if the motor is run under no load, while consistently pressing the reset button on the control panel it is
possible to accurately determine the % drop in load. This is achieved by setting the“MIN LOAD % MLC AMPS”dial to the minimum
value and then rotating the setting knob slowly clockwise until the MIN LOAD LED lights up. Leave this as a final setting.
No additional features can be set OR disabled on site.
5. Adding or Removing Features on Site
6. Thermal Trip Curves
KB LV MOTOR PROTECTION RELAY KB LV MOTOR PROTECTION RELAY
Ensure that the selected KB relay does in fact cover the full load current range of the protected
motor. Note that the models KB 1; KB 5; KB 10 and KB 25 do not require any additional current
transformers. The relay MUST be installed in the MAIN CIRCUIT of the starter. Being compact in
design the built-in single-turn feed-through primary winding transformers permit the main circuit
cable conductors of up to 7 mm to pass through the protection relay. In the case of the models
KB 50; KB 100 and KB 200 interposing current transformers of 50:5; 100:5 and 200:5
respectively are required. The secondary winding of these interposing current transformers are
then wired through the single-turn feed-through primary winding transformers at the rear of the
relay.
CARE SHOULD BE OBSERVED IN ENSURING THAT THE POLARITY OF THE CURRENT
TRANSFORMERS IS THE SAME FOR EACH PHASE AND THAT THE DIRECTION OF
CURRENT FLOW FROM THE SECONDARY SIDE OF THE TRANSFORMERS IS UNIFORM
FOR ALL PHASES. If this is not done, nuisance unbalance trips will occur.
The KB range of relays is designed for chassis mounting and once installed will require an
auxiliary supply of either 110 OR 220 Volt ac to terminals 12 and 13 OR 11 and 13 as
appropriate.
Connect the N.C contact in series with your trip circuit, (usually the main contactor holding coil)
and, if required, the N.O contact can be used for signalling or control purposes. These are
potential free contacts. Terminals 7, 8 and 9, 10 refers.
Proceed to set the motor full load current on the “MAX LOAD CURRENT AMPS” dial.
Approximate (unless you already know) the percentage drop in load the fully loaded motor will
experience during a no load condition and set that % value on the “MIN LOAD % MLC AMPS”
dial.
Set the auto/manual reset toggle switch to your preferred state after an overload trip condition.
The motor protection relay is now ready.
Tip:
Applicable once the motor is running. When using the KB motor protection relay on an application where the motor load is
relatively constant it may be a good idea to set the “Maximum Load Current Amps” dial to coincide with the actual mechanical
load being drawn by the motor. This can be achieved by holding in the reset button while at the same time slowly turning
counter clockwise on the “MAXIMUM LOAD CURRENT AMPS” dial until the red “Overload” LED lights up. When this point is
reached, you will have established the actual load current being drawn by the protected motor. Now, while still holding down
the reset button gently turn the “Maximum Load Current” dial clockwise until the “overload” LED extinguishes and leave as
a final setting. The result of this setting up method will enhance the protection to the motor in that frequent overload trips
would signal possible bearing degradation which would translate as extra abnormal load to the motor in overcoming additional
frictional forces.
4. Setting up Procedure
