Mitsubishi Electric FR-A700 Technical Manual page 504

(3) BU type brake unit and discharging
resistor
1) Installation position
For the installation position of the discharging
resistor, refer to paragraph (2), part 1).
2) Wiring
(a) When wiring the brake unit (BU type) and
discharging resistor, note high DC voltage
application
generated heat.
(b) Minimize the cable length between the
inverter and brake unit and the discharging
resistor and brake unit. If it exceeds 2m, twist
the cables. (If twisted, the distance must not
exceed 5m)
P
Inverter
N
2m or less
P
Inverter
N
5m or less
Wiring the BU brake unit
(c) When wiring the discharging resistor, the
resistor-generated heat (maximum surface
temperature is approximately 150 to 300
must be taken into consideration.
• Take measures to prevent the cables
from making contact with the resistor.
• Use heat-resistant cables (such as
glass-braided cables),
cables with silicone tubes.
(d) Use cables of the size below or larger size.
Cables applicable to the BU brake unit
BU Brake Unit Type
200V
400V
(e) Connect the cables so that the terminal
symbols of the brake unit match those of the
inverter. When the FR-HEL power-factor
improving reactor has been connected, do not
connect the brake unit to terminal P1 to
protect the brake unit from damage.
Brake unit
P P
N N
Incorrect connection examples
and discharging resistor-
P
Discharging
Brake
resistor
unit
N PR
2m or less
P
Discharging
Brake
resistor
unit
N PR
5m or less
or cover the
Cable Size
BU-1500, 3700
2mm
BU-7.5K, 15K
3.5mm
BU-H7.5K
2mm
BU-H15K, H30K
3.5mm
Brake unit
P1 P
FR-
P
HEL
N N
(f) If the transistors in the brake unit become
(4) FR-BU2/FR-BU/MT-BU5 brake unit and
resistor unit
1) Installation position
Always install the brake unit and resistor unit on a
vertical surface in the vertical direction. Installing
them in the horizontal direction or on a horizontal
surface reduces the heat dissipation effect.
Since the case temperature of the resistor unit
rises to or above 100
the brake resistor of the MT-BU5 is 300K), install
the unit in a place where it will not make contact
with cables and flammables.
2) Wiring
(a) When wiring the brake unit (FR-BU2/FR-BU/
(b) Minimize the cable length between the
)
Inverter
Inverter
2
2
2
*
2
Wiring the FR-BU2/FR-BU/MT-BU5 brake unit
538
faulty, the resistor can be unusually hot,
causing a fire. Therefore, install a magnetic
contactor on the inverter's input side to
configure a circuit so that a current is shut off
in case of fault.
(the temperature rise of
MT-BU5) and resistor unit, note high DC
voltage application and resistor unit generated
heat.
inverter and brake unit and the resistor unit
and brake unit. Use a twisted cable when the
wiring length exceeds 5m.
(Even when the wiring is twisted, the cable
length must not exceed 10m.)
P
P
Brake
unit
N
N PR
*
5m or less
5m or less
P
P
Brake
unit
PR
N N
*
10m or less 10m or less
The MT-BU5 is installed within a distance of
the supplied cable (P, N, drive signal) reaches
the inverter.
Refer to the inverter manual.
SELECTION
P
Resistor
PR
unit
P
Resistor
PR unit