Cat. No. N142-E1-02
Single-phase Current Relay
K8AB-AS
11
For a 5 A motor, the startup current would be approximately
30 A. The startup current would thus exceed the overload
capacity of the K8AB-AS1 or K8AB-AS2 (150% of rated
current for 1 s).
It is thus necessary to use the K8AB-AS3 to monitor a motor
load. (K8AB-AS3 overload capacity: 120% of rated current
continuously, 200% of rated current for 30 s, and 600% of
rated current for 1 s)
The K8AB-AS3 has a wide input range, so wind the wire
around the CT several times.
Reason for Winding the Wire around the CT
Used with the K8AB-AS3
Example: Monitoring Overloads for a Motor Rated at 5 A
K8AB Settings
Overcurrent detection, operating value: 25%, operating time: 0.1 s,
startup lock timer: 0.1 to 30 s (set according to the duration of the
startup current)
The K8AB-AS3 can be set to between 10% to 100% of the rated
current (10 A to 100 A). The wire is wound five times around the CT
so that a current of 10 A or greater will flow. This will make the input
current to the K8AB 5 A/winding x 5 windings, or 25 A.
If there is a startup current that is 6 times the rated current, the
startup current would be 25 A
×
6, or 150 A (i.e., 150% of the rated
current). The overload capacity of the K8AB-AS3 is 200% of the
rated current for 30 s, so the K8AB-AS3 would not fail even if the
startup current continued for 30 s, enabling overload detection.
500%
100%
Motor current (as percentage of r
ated current)
Several seconds to
several tens of seconds
Time from beginning of startup
To the K8AB-AS3
Primary side conductor
K8AC-CT200L