Drive A1 Submenu
54
Detailed descriptions
FLUX WEAKENING
i
The HPV 900 Series 2 will calculate the rated
flux level by using the following motor
parameters:
rated motor voltage
rated motor current
rated excitation frequency
stator resistance
stator and rotor leakage reactances
As motor speed increases, the drive will
calculate the maximum available flux and
decrease the flux automatically. This ‘field
weakening’ will cause less torque to be
available during this time.
In the HPV 900 Series 2 , 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.
However, this increased torque capability
requires more than 100% motor current to
produce 100% torque at rated speed.
Flux Weakening Parameters
The following three HPV 900 Series 2
parameters affect both the available torque
curve and flux level curve:
Motor Torque Limit
Regenerative Mode Torque Limit
Flux Weakening Factor
i
Parameter accessible through
CLOSED LOOP (U9)
ii
Parameter accessibly through
PM (U9)
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 900 Series 2 has the
Flux Weakening Factor parameter, which
effectively reduces the amount of torque
available only at the higher speeds. This will
allow the HPV 900 Series 2 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 sp
eeds…
the torque limit parameters
At high speeds…
function of the torque limit parameters and
the flux weakening factor
iii
Parameter accessible through
OPEN LOOP(U9)
torque capability &
flux level
Available Torque Curve
(limit 200%)
Available Torque Curve
(limit 250%)
speed
100 %
100 %
Flux Curve
200 %
A
A,B
B,C
C
B,C
A
A,B,C
A
torque limit = 250%
flux weakening factor = 100%
B
torque limit = 250%
flux weakening factor = 80%
C
torque limit = 200%
flux weakening factor = 100%
B
Содержание HPV 900 Series 2
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