KB Electronics KBAC-48 - Manual (Page 25)

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1. Wire an AC RMS ammeter in series with one motor phase.
2. Run the motor and set the unloaded speed to approximately 50% (900 RPM on 4-pole
1500/1725 RPM motors).
3. Using a tachometer, record the unloaded speed.
4. Load the motor to the nameplate rated current (AC Amps).
5. Adjust the COMP Trimpot until the loaded RPM is equal to the unloaded RPM.
6. The motor is now compensated to provide constant speed under varying loads.
13.7 Motor Overload (I 2 t) With RMS Current Limit (CL)* – Sets the current limit (overload), which limits
the maximum current to the motor, which prevents motor burnout and eliminates nuisance trips.
The CL Trimpot is factory set to 160% of the drive rated current. To increase the current limit, rotate
the CL Trimpot clockwise. To decrease the current limit, rotate the CL Trimpot counterclockwise. See
Figure 36 on page 24 and Figure 37.
*UL approved as an electronic overload protector for motors.
CAUTION! Adjusting the current limit above 160% of the motor nameplate rating can cause over-
heating of the motor. Consult the motor manufacturer. Do not leave the motor in a locked rotor
condition for more than a few seconds since motor damage may occur.
In order to ensure that the motor is properly protected with the I 2 t feature, it is required that
the CL Trimpot be set for 160% of the motor nameplate rated current, as described below.
Note: This adjustment must be made within 6 seconds or the I 2 t Trip will occur.
The current limit may be adjusted as follows:
1. Connect an AC RMS ammeter in series with one motor phase.
2. Set the CL Trimpot fully counterclockwise.
3. Adjust the speed setting to 30%.
4. Lock the motor shaft and adjust the CL Trimpot to 160% of the motor nameplate rated current.
Trip T
ime
(Minutes)
CL (Factory Setting)
140 110 120 130
0.1
Motor Current (%)
1
160 150
10
100
1000
Figure 37 – I 2 t Trip Time vs. Motor Current