Honeywell 4000 Serie Manual Del Usuario página 9

OPERATION
Each time actuator terminals T5 and T6 are (re)powered, the
microprocessor will cycle the valve through a full stroke to
calibrate its position. Any stroke between 1/2 in. (13 mm) and 1
in. (25 mm) will be divided into 30 equal steps. Run time is
proportional to stroke length and power supply voltage. The
actuator will also slow down as the valve closes off the seat.
The LED lights when terminals T5 and T6 are powered, and
flashes when the actuator is in motion. T5 is connected to
Terminal R in ML6984 and to Terminal W in ML7984.
NOTE: Initial calibration does not apply to ML6984 installed
for 3-wire control or installed for 5-wire control without
the 272630D position feedback/auxiliary switch mod-
ule. Span and start positions will need to be set during
controller set-up. See ML6984 Operation 3-wire,
below. ML7984 always conducts a self-calibration
sequence when (re)powering up.
ML7984 Operation
The microprocessor responds to the signal across the input
terminals based on the configuration DIP switch settings.
When correctly connected to the actuator, a control signal
between signal input terminals is converted to a digital run time
and compared to pulse counts from the first gear in the gear
train. When these counters are equal, the drive motor and
drive shaft are stationary.
As long as the value of the controlled medium remains at the
controller setpoint, the control loop circuit is in balance, and the
actuator does not run. When the controller set point or
controlled temperature changes, the controller output voltage
is changed, causing the counters to differ. As the actuator
moves in the direction to correct the difference, the counters
increment or decrement, and stop the actuator when the input
and gear counts agree.
At the end of the valve stroke, the actuator develops the
necessary force for positive valve close-off. The motor stops
automatically when the motor draws a predetermined current
which corresponds to a force level. The digital counters are
reset and calibrated at each end of stroke.
Modulating actuators will automatically travel to the position
corresponding to analog input signal following the self-
calibration cycle.
CAUTION
Disconnect power supply before beginning
installation to prevent electrical shock and
equipment damage.
All wiring must comply with applicable local electrical
codes, ordinances, and regulations.
Make certain that the voltage and frequency of the
power supply correspond to the rating of the device.
DO NOT electrically operate the MLx984 actuator
before assembly to the valve because damage not
apparent to the installer may occur.
DO NOT connect 24 Vac between any ML7984 signal
input terminals. DEVICE FAILURE WILL RESULT.
ML6984, ML7984 SERIES 4000 DIRECT COUPLED VALVE ACTUATORS
NOTE:
1. The ML7984 must be field configured with the DIP
switches which are located beside the terminal
block. See wiring diagrams for details. Turn power
off before setting any DIP switches.
2. There is a 1.5 second delay in actuator response
to every signal change. This occurs to screen out
electrical noise.
3. For proper operation, voltage on the T5 and T6
must not be less than 22 Vac or 24 Vdc during run-
ning or force generating stages. Increase trans-
former VA rating or use a model with better
regulation if voltage drops below 22 Vac when the
valve is closing off.
ML6984 Floating Operation, 5-Wire
The motor is controlled by a microprocessor. Connecting B to
R for 1/10 second or longer tells the microprocessor to cause
the actuator to drive upwards. Connecting W to R will cause
the actuator to drive downwards. For "floating" control, the
actuator will remain in the last position when there is no
connection to R.
At the end of the valve stroke, the actuator will develop the
necessary force for positive valve close-off. As forces are
developed, the current to the motor increases. The
microprocessor stops the actuator automatically when motor
current and force reaches the factory-calibrated level.
NOTE: There must be at least 1.5 second delay between
successive floating input signals. The actuator will
ignore floating signals during calibration cycle and
does not remember any pulses sent during this
period. The controller may need to run through its
own calibration cycle before use.
ML6984 Operation, 3-Wire
ML6984 may be installed like a conventional (non-electronic)
floating actuator. The interface electronics are powered at the
same time as the motor. Pulses must be at least 100 ms long
with a delay of at least 1500 ms between pulses. When
ML6984 is not powered between terminals T6 and T5/R, self-
calibration will not occur. The controller must drive the valve
through a cycle manually to calibrate stroke to the controller.
NOTE: The 272630D position feedback/auxiliary switch mod-
ule cannot be used with ML6984 3-wire installation.
The 272630D requires continuous power.
ML6984 XL10 Controller
Compatibility
XL10 controllers are designed to work with constant-speed
actuators. ML6984 actuators use direct current motors which
vary their speed as the valve seats or if power supply voltage is
not consistent. ML6984 actuators in 5-wire mode offer 30
discrete positions only. To minimize potential valve position
drift, XL10 controllers should use the 3-wire installation and be
programmed for a daily valve exercise cycle.
ML6984 On-Off Operation
For on-off operation, ML6984 requires a 24 Vac SPDT contact.
An interface relay such as RA889 is required to power the
anticipator heater of an electromechanical thermostat such as
T87F (See Fig. 17).
9 95C-10939EFS—03