4-20 Manual # 42-02-2223
Final Adjustment
6. Apply a maximum value of brake voltage, very briefly, at the start of movement. This
gets the brake quickly to the point in the lifting process where a substantial amount of
tension is released. This is done as follows:
• Set Pick voltage back to the original value to allow a high initial value of brake voltage.
• Set Repick time to 1.00 second to allow a slow transition through the pressure-releas-
ing part of movement, after which the brake voltage briefly returns to a high value to
ensure that the brake fully picks. (See the following note.)
• Increase the value of Weakening delay in 0.05 second increments until you see the
brake move more quickly in the first part of its movement so it can reach the stage
where the pressure is starting to be released. Typical values are between 0.10 to 0.45
seconds. The final result will often look as if the brake is lifting at a fairly constant rate,
even though the initial voltage is high. This overcomes the natural tendency for a gear-
less brake to start lifting slowly and then faster the further it lifts.
It is important to realize that full brake Pick voltage is automatically applied for about a second at the
end of the brake Weakening delay, just after the brake has cleared the braking surface, thereby guaran-
teeing full lifting after a smooth transition through the zone of pressure release. After the brief return to
full brake voltage, the brake voltage will automatically drop to the Hold voltage, but must not allow the
brake to sag back onto the braking surface.
• Verify the manufacturers recommended value for brake holding voltage and set Hold
voltage to that value. If this information is not available, experiment with Hold voltage
to determine the voltage necessary to hold the brake up, and then add a little extra
margin.
7. At this point, a storage oscilloscope is suggested to get the best results from adjustment.
Connect the scope to iBox test points STP2 and GND (with the iView Virtual Oscillo-
scope Test point 2 set to Speed Feedback) to view car speed response.
8. Set the horizontal sweep to about 0.5 to 0.2 second per division and increase vertical
gain until you see a microscopic view of the breakaway at the start of movement. A
rough start is characterized by jaggedness at the beginning of the curve; a smooth start
by a smooth transition from the horizontal line to the acceleration curve. Using this
method, you can touch up parameters such as Speed pick delay 1 in the next step.
9. On the Configuration > Pattern > Common tab, set Pattern scaling to 100%.
10. Coordinate the start of the car with brake operation by increasing Speed pick delay 1
(Configuration > Brake > Control tab) until you begin to see rollback at the start of an
empty car DOWN run at the top floor. Then, decrease Speed pick delay 1 until rollback
just disappears.
It may be helpful to reduce the Initial jerk parameter to 5.00 or 4.00 to help provide a smooth
start. Remember that any change in the brake parameters, Initial jerk, or any of the gain
parameters relating to the speed loop will probably affect the coordination of the starts. There-
fore, you must readjust Speed pick delay 1 after any such changes.
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