ABB DCS 500B, Description

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Functional Software description
60 DCS 500 Software Description
Field heating
when in "OFF"-
state The motor field can have a small value in order to avoid condensa-
tion when motor is in "OFF"-state. The function can be activated by
means of parameter:
FIELD HEAT SEL (914)
The used current references are the same as with the field reduc-
tion function:
F1 RED REF (1314) reference for the first motor
F2 RED REF (1511) reference for the second motor in the
case of shared motion.
The function is activated when command "ON" is 0, ie., the main
contactor is open. The function closes the field contactor.
EMF_CONTROL
function block
Field Weakening Point
Speed
U armature
Excitation
U
I exc.
Figure 44 Field weakening as a function of speed
The Purpose of
EMF Controller The EMF-controller has two main control functions:
1.
When the motor is run above the base speed, the EMF-
controller reduces the motor field to keep the EMF-voltage
constant at a maximum level. This must be done to avoid ar-
mature overvoltage and on the other hand, a maximum EMF is
needed to keep the FLUX as high as possible.
2. When an accurate torque controller loop is needed, the EMF
controller can be used to form an accurate FLUX value. The
application program in the DCS 500B calculates the required
value of the motor EMF at the used speed and used FLUX
reference. The EMF-controller then adjusts the field current so
that the measured EMF corresponds to the EMF-reference.