Mitsubishi Electric MELSERVO-J2S Series Transition Handbook page 210

Part 5: Review on Replacement of MR-J2S-30 kW or Higher Capacity Models with MR-J4-DU_
(b) When connecting one converter unit to two brake units
POINT
When connecting two brake units in parallel, use FR-BU2-(H) for both.
Otherwise an alarm or malfunction may occur.
Make sure to connect the master and slave terminals (MSG, SD) of one brake
unit to those of the other respectively.
Do not connect as shown below.
Converter unit
L+
L-
Connecting multiple brake
units together to L+ and L-.
Brake unit
P/+
N/-
Brake unit
P/+
N/-
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Converter unit
L+
L-
Connecting multiple brake
units by daisy chain.
Brake unit
P/+
N/-
Brake unit
P/+
N/-