Submittal Sheet

ML6984, ML7984 SERIES 4000 DIRECT COUPLED VALVE ACTUATORS
9
95C-10939—6
OPERATION
Each time actuator terminals T5 and T6 are (re)powered,
the mi cro proc es sor 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 ter mi nals
T5 and T6 are pow ered, and fl ashes when the ac tu a tor is
in motion. T5 is con nect ed to Terminal R in ML6984 and to
Terminal W in ML7984.
NOTE: Initial callibration does not apply to ML6984
installed for 3-wire control or installed for 5-wire
control without the 272630D position feedback/
auxiliary switch module. Span and start po si tions
will need to be set dur ing con trol ler set-up. See
ML6984 Op er a tion 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 con fi g u ra tion 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 fi rst 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 di rec tion to correct the difference,
the counters increment or dec re ment, 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
equip ment damage.
All wiring must comply with applicable local
electrical codes, ordinances, and regulations.
Make certain that the voltage and frequency of the
power supply cor re spond 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 FAIL URE
WILL RESULT.
NOTE:
1. The ML7984 must be fi eld confi gured 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
running or force generating stages. Increase
transformer 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 ac tu a tor to drive upwards. Connecting W to R
will cause the ac tu a tor to drive downwards. For “fl oating”
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 nec es sary force for positive valve close-off. As forces
are developed, the current to the motor increases. The
mi cro proc es sor stops the ac tu a tor automatically
when motor current and force reaches the fac to ry-
calibrated level.
NOTE: There must be at least 1.5 second delay between
successive fl oating input signals. The actuator will
ignore fl oating 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) fl oating 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
module cannot be used with ML6984
3-wire installation. The 272630D requires
continuous power.