External Soft Start Circuit Control - Control Techniques Unidrive Installation Manual

4.8

External soft start circuit control

As discussed in section 4.4 External softstart resistor on page 12 an external soft start
resistor is required for Unidrive SP size 4 and larger.
The soft start resistor only needs to be in circuit at certain times as shown in the flow
diagram below.
Figure 4-13 Soft start control circuit sequencing
The above sequencing can be achieved using the drive internal function blocks as
shown in Figure 4-14 on page 28.
Unidrive SP Low Voltage DC Installation Guide
Issue Number: 1
Is the drive powered
from LVDC ?
(Read Pr 6.44)
Is the drive in
Yes
UV state?
(Read Pr 10.16)
Wait 2.5 . s
Close the drive
relay
(soft start resitor
out of circuit)
Allow drive
enable
(write 1 to Pr 6.15)
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No
Yes
No
27