User guide

CME 2 User Guide I
2
T Time Limit Algorithm
Copley Controls 195
even though the commanded current remains at 12 A. The I
2
T Accumulator Variable value
remains constant during the next 2 seconds since the difference between the actual
output current and the continuous current limit is zero.
At approximately 3.5 seconds, the commanded current falls below the continuous current
limit and once again the output current follows the commanded current. Because the
actual current is less than the continuous current, the I
2
T Accumulator Variable value
begins to fall incrementally.
The I
2
T Accumulator Variable value continues to fall until at approximately 5.0 seconds
when the commanded current goes above the continuous current limit again. The actual
output current follows the current command until the I
2
T Accumulator Variable value
reaches the I
2
T setpoint and current limiting is invoked.
D.2: I
2
T Scope Trace Variables
Two Scope Tool trace variables are available for monitoring whether the I
2
T accumulator
is accumulating or discharging.
The I
2
T Amplifier Accumulator variable evaluates the accumulator against the factory set
current limits of the amplifier.
The I
2
T Motor Accumulator variable evaluates the accumulator against the user-
programmed current loop values.
The value shown in the scope has been normalized so that 100% equals the I
2
T setpoint.
When either trace variable line reaches 100%, current limiting will be invoked.
For instructions on using these variables in the Scope Tool, see Trace Channel Variable
Parameters (p. 156).