YASKAWA CR700, Technical Manual, Page: 237 / 886

Startup
Procedure
and
Test
Run
3
3.11 Problems that Can Frequently Occur during Setup and Possible Solutions
YASKAWA SIEPC71061723A YASKAWA AC Drive CR700 Technical Manual 237
Torque and current are proportionally related when flux is constant. These are possible methods for suppressing
current at start.
• Method 1: Quickly generate flux.
– Initial excitation
– DC Inject Braking at Start
– Magnetic Flux Compensation
• Method 2: If using V/f control or OLV control, set the highest value possible for the V/f pattern.
Table 3.28 How To Generate Flux Quickly and its Effectiveness
Type Description
Basic type
There is a delay in magnetic flux developing after start. Secondary circuit
time constant: The value of [T] is displayed in the drive monitor as the
torque reference, so it is possible to see that the torque limit is not operating
if magnetic flux compensation is active. However, the torque limit is [Iq]
limit, so it is not a problem in this situation. The effectiveness of the torque
limit can be confirmed by checking the current level.
Initial Excitation
through an External
Terminal
(CLVonly)
-
DC Inject Braking at
Start
(All control
methods)
It is possible to start operating after a bit of flux has built up. However, it
can take over 1 s for flux to build up in mid-sized motors. Some adjustment
is necessary because waiting for over 1 s will decrease the responsiveness of
the drive.
Note:
Usually, set between 0.2 s and 0.3 s.
Magnetic Flux
Compensation
(OLV Control)
The purpose of this function is to build up magnetic flux more quickly by
allowing a large amount of flux current to flow at start using the percentage
set in b2-08 [Magnetic Flux Compensation Value] . Magnetic flux
compensation of 200% generates 1/2 for the flux build up.
Note:
Set b2-03 [DC Inject Braking Time at Start] to adjust this level.
Field Forcing
*1
The upper limit value for d6-06 [Field Forcing Limit] is 400%, which
allows flux current to flow at start up for the purpose of compensating for
the delay in flux build up. If the value set in d6-06 is set too high, this will
increase the amount of lurching at start. Set an appropriate value between
200% and 400%.
Note:
Speed Control must be active to make these adjustments. You cannot
make adjustments during DC Injection Braking at start or at stop.
*1 Field Forcing is enabled when
d6-03 = 1 [Field Forcing Selection = Enabled]
, and when using CLV control or OLV control.