3. System Design
MV3DB Series DB Units
ALSPA MV3000e Dynamic Braking Units
(07/06)
Page 3-8
MV3000
Drive Unit
AC
Line
Reactor
DC rated
Contactor
Fused
Mains
Input
R
S
T
DB Resistor
U
V
W
External
Supply
M
3
BR (DB Unit)
DC+
Digital
Input
Isolation
Barriers
Figure 3-5 DB resistor protection by disconnection
For the method shown in Figure 3-5, if it is required to warn the drive when the DB resistor has
been disconnected, one possible solution would be to use a contactor having a volts-free
auxiliary contact and connect this to activate a drive digital input to flag a warning. Alternatively
a lower rated thermostat could be used to warn of imminent disconnection. In either case, the
contact connected to the digital input must be rated for double or re-inforced insulation to
prevent dangerous voltages being transmitted to the drive control terminals. Control wiring
must be segregated from power wiring as shown in Section 3.9 and in Section 3 of the drive
Getting Started Manual.
3.9
Cabinet layout and EMC
Figure 3-6 shows a typical layout and EMC segregation requirements for a braking resistor
mounted on top of the drive cabinet.
To minimise radiated noise emissions, the braking resistor should be mounted in a suitably
ventilated metal enclosure. Power cables between the resistor and the cabinet should be
overall screened (shielded), with the screens bonded to both enclosures.
