Closed-loop Drive A1
88
parameter may need adjustment to reduce the
effects of field weakening.
REGEN TORQ LIMIT
(Regenerating Current Limit)
This parameter sets the maximum amount of
regenerative torque the drive will see during
regeneration. This parameter may need
adjustment to reduce the effects of field
weakening.
FLUX WKN FACTOR
(Flux Weakening Factor)
This parameter limits the maximum amount of
torque available at higher speeds. When the
drive is commanding higher speeds, this
parameter defines a percentage of the defined
torque limits (MTR TORQUE LIMIT (A1) and
REGEN TORQ LIMIT (A1)). This parameter is
used to reduce the effects of field weakening
and reduce the amount of motor current
produced at higher speeds.
In the HPV 600, flux weakening begins before
the motor reaches rated speed.
The drive can supply more than 100% current,
since the CEMF is lower. Therefore, the drive
can produce more than 100% of the motor’s
rated torque at the rated speed.
Flux Weakening Parameters
The following three HPV 600 parameters effect
both the available torque curve and flux level
curve:
•
Motor Torque Limit (MTR TORQUE
LIMIT(A1))
•
Regenerative Mode Torque Limit (REGEN
TORQ LIMIT(A1))
•
Flux Weakening Factor (FLUX WKN
FACTOR(A1))
The highest of the two torque limits is used as
the torque limit that defines the two curves.
An example of the effects of the torque limit on
the amount of flux weakening needed and the
amount of torque available through the entire
speed range is shown below.
By lowering the torque limit you can effectively
reduce the amount of field weakening needed
and reduce the amount of current needed by the
motor at motor’s rated speed. The trade-off is
you have lower over-all torque available.
In order to have more torque available at the
lower speeds, the HPV 600 has the Flux
Weakening Factor parameter, which effectively
reduces the amount of torque available only at
the higher speeds. This will allow the HPV 600
to have a higher flux level at the motor’s rated
speed and require less current to produce rated
torque.
An example of the effects of the flux weakening
factor on the amount of flux weakening needed
and the amount of torque available through the
entire speed range is also shown below.
The maximum amount of torque available can
be defined as the following:
•
At low speeds…the torque limit parameters
•
At high speeds…function of the torque limit
parameters and the flux weakening factor
Speed-Torque Curves (Examples)
ANA 1 OUT OFFSET
(Digital to Analog #1 Output Offset)
Offset for scaling Analog Output Channel #1.
voltage
output
channel
analog
GAIN
OUT
ANA
OFFSET
OUT
ANA
creates
software
drive
signal
=
×
−
Available Torque Curve
(limit 200%)
Available Torque Curve
(limit 250%)
torque capability &
flux level
speed
100 %
100 %
Flux Curve
200 %
A
A,B
B,C
C
B,C
A
A,B,C
B
250 %
A: torque limit = 250% / flux weakening factor = 100%
B: torque limit = 250% / flux weakening factor = 80%
C: torque limit = 200% / flux weakening factor = 100%