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CURRENT
REDUCTION
RESISTOR
SECTION 15
AUTOMATIC CURRENT REDUCTION
Built into the IM481H is the ability to automatically reduce the current in the motor
windings after the completion of a move. The reduction occurs approximately .5 seconds
after the last positive going edge of the Step Clock input. The IM481H will then revert
back to the original current setting at the next positive going edge of the Step Clock input.
To utilize this feature, the current reference output must be used to adjust the output
current of the IM481H and a resistor must be connected between pins 3 & 4 (see Figure
6). The value of the resistor will determine the amount of current reduction.
The amount of current per phase in the current reduction mode is related to the value of
the current reference resistor and the current reduction resistor. When the current
reduction circuit is activated, the current reduction resistor is paralleled with the current
adjustment resistor. The parallel combination of the current reference and current
reduction resistors determine the reduced current level. The relationship between the
output current and the resistor's values is as follows:
.001 x *R(Current Adjust) x R(Current Reduction)
Output Current Reduced (Amps)=
R(Current Adjust) + R(Current Reduction)
OR
Output Current Reduced x R(Current Adjust)
R(Current Reduction) =
.001 x R(Current Adjust) - Output Current Reduced
NOTE: Resistor values are in ohms.
19
Figure 11
When connecting the current reduction resistor between pins 4 and 5, the
connections should be made as short as possible to help minimize noise
coupled into the driver.
NOTE:
CURRENT
ADJUSTMENT
RESISTOR