7-9-22
Pre-excitation
The motor generates torque through magnetic flux and torque current. Since the establishment of
magnetic flux has a lag element, suf
ficient torque is not generated at the time of starting.
Pre-excitation is a function for establishing the magnetic flux before startup to ensure sufficient torque
even during the time of starting.
There are two methods for issuing pre-excitation commands: one is to execute for the period of Pre-
excitation Timer (H85) after the RUN command is turned ON, and the other is to turn ON the EXITE
terminal and apply pre-excitation until the RUN command is input.
Controlling by Pre-excitation Timer
When the pre-excitation (Timer) elapses, it is judged that magnetic flux has been established, and ac-
celeration is started. Secure sufficient time for establishment of magnetic flux with Pre-excitation Timer
(H85).
The appropriate value of the pre-excitation (Timer) is dif
ferent for each capacity. As a standard, con-
sider it equivalent to the default value of the Power Interruption Restart Wait Time (H13).
This function is disabled when the pre-excitation timer is set to 0.00.
Parameter No. Function name Data Default data Unit
H85
Pre-excitation Timer 0.00: Disable
0.01 to 30.00
0.00 s
H84
Pre-excitation Level
*1
100 to 400
100 %
*1. Pre-excitation Level (H84) sets the ratio with the rated magnetic flux as 100%. This is used to raise the out-
put current to more than specified to shorten the pre-excitation timer. Generally, there is no need to change
the settings. If a set value is too large, instantaneous overcurrent (alarm code: OC) sometimes is generated.
Motor speed
Magnetic flux
Rated magnetic flux
ON
FW
Pre-excitation Timer (H85)
Controlling by Pre-excitation Command Terminal (32: EXITE)
Pre-excitation starts operating when the EXITE terminal is turned ON regardless of the setting of Pre-
excitation Timer (H85). After this, when the RUN command is input, pre-excitation operation ends, and
acceleration starts. When the time until the RUN command is input is short, establishment of magnetic
flux sometimes does not arrive at a sufficient level. In this case, lengthen the time until the RUN com-
mand is input.
7 Other Functions
7-151
M1 Series Standard Type User's Manual (I669)
7-9 Other Operation Functions
7
7-9-22 Pre-excitation
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