Tempco TEC-2500, Инструкция по эксплуатации

Страница: 73 / 108

69
4–12 Pump Control
Pump control function is one of the unique features of the TEC-2500. Using this
function, the pressure in a process can be excellently controlled. The pressure in a
process is commonly generated by a pump driven by a variable speed motor. The
complete system has the following characteristics which affect control behavior.
1. The system is very noisy.
2. The pressure changes very rapidly.
3. The pump characteristics are ultra nonlinear with respect to its speed.
4. The pump can't generate any more pressure if its speed is lower than half of its rating
speed.
5. An ordinary pump may slowly lose pressure even if the valves are completely closed.
Obviously, a conventional controller can't fulfill the conditions mentioned above. Only
the superior noise rejection capability in addition to the fast sampling rate possessed
by the TEC-2500 can handle such an application. To achieve this, set the following
parameters in the setup menu:
FUNC=FULL
EIFN=NONE
PVMD=PV1
FILT=0.5
SELF=NONE
SPMD=PUMP
SP2F=DEVI
and program the following parameters in the user menu:
REFC=reference constant
SP2=a negative value added to SP1 to obtain the set point for the idle state
Since the pump can't produce any more pressure at lower speeds, the pump may not
stop running even if the pressure has reached the set point. If this happens, the pump
will be overly worn and waste additional power. To avoid this, the TEC-2500 provides a
reference constant REFC in the user menu.
If PUMP is selected for SPMD, the controller will periodically test the process by using
this reference constant after the pressure has reached its set point. If the test shows
that the pressure is still consumed by the process, the controller will continue to supply
appropriate power to the pump. If the test shows that the pressure is not consumed by
the process, the controller will gradually decrease the power to the pump until the pump
stops running. When this happens, the controller enters an idle state. The idle state will
use a lower set point which is obtained by adding SP2 to SP1 until the pressure falls
below this set point. The idle state is provided for the purpose of preventing the pump
from being restarted too frequently. The value of SP2 should be negative to ensure that
the controller functions correctly.
The pump functions are summarized as follows:
1. If the process is demanding material (i.e., loses pressure), the controller will
precisely control the pressure at the set point.
2. If the process no longer consumes material, the controller will shut off the pump for
as long as possible.
3. The controller will restart the pump to control the pressure at the set point as soon
as the material is demanded again when the pressure falls below a predetermined
value (i.e., SP1+SP2).
PUMP:
A cost effective solution
Key menu
SPMD
SP2F
REFC
SP2
Pump control features:
1. Minimum oscillation of
pressure
2. Rapidly stabilized
3. Guaranteed pump stop
4. Programmable pump
stopping interval