YASKAWA VARISPEED-616G5, Instruction Manual

Page: 198 / 355

7.5.1 Application Constants: b
Advanced Operation
7 - 44
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Magnetic Flux Compensation: b2-08 (for SPEC: F)
When the DC injection braking time at start (initial excitation) function is used to start the motor magnetic
flux before operating machinery requiring high starting torque, particularly with large-capacity motors,
the startup of the magnetic flux may take some time due to the effect of the electrical time constants of the
motor.
Use the magnetic flux compensation function to supply a strong magnetic flux current when starting the
DC injection braking time at start (initial excitation). This will increase the speed and stability of the mo-
tor’s internal magnetic flux startup.
User
Change
during Setting Factory
Valid Access Levels
User
Constant
Number
Name
g
during
Opera-
tion
Setting
Range
Unit Factory
Setting
V/f
Control
V/f with
PG
Open
Loop
Vector
Flux
Vector
b2-03
DC injection braking
time at start
×
0.00 to
10.00
0.01
s
0.00 B B B B
b2-08
Magnetic flux com-
pensation volume
×
0 to 500* 1% 0
× ×
A A
When b2-08 is 100%, it indicates the motor no-load current (notor magnetic flux current).
Run command
Output frequency
b2-08
b2-08=100%
Limited to smaller of 80% of the Inverter’s rated
current or the motor’s rated current.
Motor’s magnetic flux current
Control mode
During base block During speed control
b2-03
Motor’s magnetic flux
current during control
During DC injection braking time at start (initial excitation)
Fig 7.20 Time Chart for Magnetic Flux Compensation
D
If b2-08 is set at 100% or greater, a stronger current can be supplied when starting DC injection braking
time at start (initial excitation), and the motor’s internal magnetic flux startup can be speeded up. The
startup time can be reduced by approximately half when the b2-08 is set to 200%.
D
The magnetic flux startup is slower if b2-08 is less than 100%. (Do not normally set b2-08 to less than
100%. However, the operation will be the same as b2-08=100% when b2-08=0%, and the startup will
be at the set DC injection braking current (b2-02).
D
If the magnetic flux compensation volume (b2-08) is set to a large value, there may be greater noise
generated from the motor during DC injection braking time at start.
D
The electrical time constant when the motor’s magnetic flux is started (secondary circuit time constant)
can be calculated using the motor constant E2 setting and the following formula:
Secondary circuit time constant T2 = [(E2-01
2
-E2-03
2
)
1/2
/(2
π
x E2-02 x E2-03)] (sec)
D
Do not use this function when slow commencement of braking due to DC injection braking time at
start (initial excitation) is becoming a problem. Use the separate DC braking command (setting: 60)
for multi-function contact input , and start the motor magnetic flux beforehand while stopping the mo-
tor.
J
Speed Search: b3-01 to b3-03
The speed search function finds the speed of a coasting motor and starts up smoothly from that speed. It
is effective in situations such as switching from a commercial power supply.
Speed Search Selection at Start: b3-01
User
Change
during
Setting Factory
Valid Access Levels
User
Constant
Number
Name
g
during
Opera-
tion
Setting
Range
Unit Factory
Setting
V/f
Control
V/f with
PG
Open
Loop
Vector
Flux
Vector
b3-01
Speed search selec-
tion at start
×
0, 1 − 0 * A A A A
* When the control method is switched, the factory setting changes as follows:
V/f control: 0; V/f with PG: 1; open-loop vector 0; flux vector: 1
7