4-160
Notes:
1.
The time for the flux to reach 100% is a function of the
motor’s electrical time constant, see figure 4.3.62.
2.
Electrical time constant can be calculated by using the motor parameter settings (group 02).
Motor leakage inductance (02-17) + motor mutual inductance (02-18)
Electrical time constant T2 =
Motor leakage resistance
Set the pre-excitation time (07-37) based on the electrical time constant T2
07-38 Pre-excitation initial level
Use the pre-excitation initial level (07-38) to provide a higher excitation current during the pre-excitation time
(07-37); this will increase the speed and stability for motors.
In order to quickly magnetize the motor, reduce the pre-excitation time (07-37) and set the pre-excitation level
(07-38) to a high level.
If 07-38 is set to a value greater than 100%, providing a high excitation current during the pre-excitation time
(07-37), the
motor’s magnetization time is shorted. When the setting reaches 200%, magnetization is reduced by
roughly half.
A high pre-excitation level (07-15) might result in excessive motor sound during pre-excitation.
When the flux reaches 100%, pre-excitation current reverts back to 100% and pre-excitation is completed, refer to
figure 4.3.62 for more information.
Run
command
Magnetic
flux and
Excitation
current
100%
Motor speed
Excitation current
Pre-excitation initial level (07-38)
Magnetic flux
Pre-excitation time
t
t
t
Figure 4.3.62 Pre-excitation operation
