Honeywell UDC 3300 manual Three Position Step Control Algorithm, Power-up output

5.16 Three Position Step Control Algorithm

Introduction	The Three Position Step Control algorithm (Loop 1 only) allows the
	control of a valve (or other actuator) with an electric motor driven by two
	controller output relays; one to move the motor upscale, the other to move
	it downscale, without a feedback slidewire linked to the motor shaft.
	Accutune SP or SP+PV tuning does not function with this algorithm.
	Accutune TUNE will operate with this algorithm.

Estimated motor position

Accurate motor position

Displaying the motor position

Models DC330X-EE-XXX-X0, DC330X-AA-XXX-X0

The Three Position Step control algorithm provides an output display (OUT) which is an estimated motor position since the motor is not using any feedback. Although this output indication is only accurate to a few percent, it is corrected each time the controller drives the motor to one of its stops (0 % or 100 %).

It avoids all the control problems associated with the feedback slidewire (wear, dirt, noise). When operating in this algorithm, the estimated “OUT” display is shown to the nearest percent (i.e. no decimal).

Models DC330X-EE-XXX-X2, DC330X-AA-XXX-X2

In the event that an accurate and repeatable indication in motor position is required, Position Proportional model’s slidewire input can be used to read the motor position and display it on the lower display as “POS” while still operating in the Three Position Step control mode.

The slidewire must be calibrated for this to operate correctly.

Table 5-29 lists the procedure for displaying the motor position.

Table 5-29 Procedure for Displaying the 3PSTEP Motor Position

Step

1

Operation

Access the displays

Press

LOWER DISPLAY

Action

until you see:

Upper Display

The PV value

Lower Display

POS = 3PStep motor position with slidewire connected

or

OUT = Estimated 3PStep motor position when no slidewire exists

Power-up output

When the controller powers up after a power outage, the position of the motor will correspond to whatever was configured at the Control Set Up function prompt PWR OUT, selection LAST or F’SAFE. Refer to Section 4.10, Table 4-9for definition of each selection.

182 UDC 3300 Controller Product Manual 4/00