Walker Magnetics SMART-D SERIES - Manual (Page 19)

O.S. WALKER Co., Inc. SMART-D Control
SMART D MANUAL DD14511L Rev. L, March 30, 2011
4-5
4.6 Control Protection
If the control is switched into sudden high power operation with too large a load, the AC fuse
may blow before the electronic protective circuits can function.
If the chuck control is overloaded by a short circuit or a chuck too large for this control's rating,
the control will sense this condition and will attempt to protect itself by flashing all the system
indicator lights, and the control will not respond to any function selection. This will continue
until AC power is removed from the control and the problem is corrected.
The logic section of the Main PC Board is protected by a .125A fuse in location F1. This fuse
will blow if a problem occurs in the logic section.
If AC power is interrupted while the control is running, the control returns to the mode of
operation selected just prior to loss of power. This allows easy resumption of machining after
an AC line dropout.
4.7 Release Cycle Steps
The Release Cycle removes residual magnetism in the chuck and workpiece by sending
decreasing, alternating pulses of DC voltage through the chuck coils. The amount of
demagnetization (DEMAG) depends upon the number of pulses, the length of time that the
pulses are applied (T = Pulse width) and the time between pulses (t = Off Time). The first
pulse is always negative. The pulse voltages are determined automatically by the chuck
control software. The number of demagnetization pulses are adjustable from one to sixteen
(1-16). The pulse width and off time are automatically adjusted by the on-board
microprocessor. See Figure 4-1.