System Design; Required Connections For Low Voltage Dc Operation; Low Voltage Dc Power Supply - Control Techniques Unidrive Installation Manual

4

System design

4.1

Required connections for Low Voltage DC operation

Table 4-1 illustrates what connections and voltage supplies are required for Low Voltage
DC operation.
Table 4-1 Required connections for Low Voltage DC operation
Drive Control +24V
size external input
1
2
3
4
5
6
SPMA
SPMD
4.2

Low Voltage DC power supply

The supply should meet the requirements set out in section 3.1.2 Low Voltage DC
rating on page 9.
If the Low Voltage DC supply is in the form of a battery and the voltage drops below 36V
a UV trip will occur. A UV trip automatically resets if the DC bus is back within
specification, which means it is possible for the drive to cycle in and out of the trip state
if the drop in voltage only occurs under load.
I.e. The drive is in the 'rdy' condition and the DC bus is within specification. The drive is
given the run command, which enables the output causing current to flow. The DC bus
drops and a UV trip is seen, the drive output is thus disabled. The DC bus then rises
back to the previous level and the UV trip resets. If the run command is still present the
drive output is enabled, which causes current to flow etc.
One of the following should be implemented to prevent this loop from occurring:
1. SM-Applications module not used: A threshold from menu 12 should be used to
monitor the DC bus and trip the drive should it drop below normal operating levels
with a charged battery.
2. SM-Applications module used: A software trap should be added to prevent this loop
from occurring.
Unidrive SP Low Voltage DC Installation Guide
Issue Number: 1
24V Low Voltage
DC mode enable
x
x
x
www.controltechniques.com
Connection
LVDC supply
to 48V
+DC/ -DC
terminal
x
x
x
x
x
External soft
start resistor
x
x
x
11