2 Engineering
2.10 Switching to the output side
DC1 Variable Frequency Drive 04/16 MN04020003Z-EN www.eaton.com 51
2.10.3 Bypass circuit
If a bypass is required, use mechanically linked switches or contactors or
electrically interlocked contactors in order to ensure that the motor terminals
will not be simultaneously connected to the mains connection and to the
variable frequency drive’s output terminals.
When the motor is being switched off, the output (U, V, W) of variable
frequency drive T1 must be disabled (the FWD/REV enable signal must be
switched off) before the contacts at S1 are opened.
WARNING
Never connect the DC1 variable frequency drive’s output
terminals U, V, and W to the power feed system (L1, L2, L3)!
Connecting the mains voltage to the output terminals can result
in the variable frequency drive being irreparably damaged.
a Q1 thermal overload and short-circuit protection
b F1 fuse and F2 overload relay (alternative to ①)
Q1 Mains contactor
T1 DC1 variable frequency drive
S1 Interlocked switching between variable frequency drive
and bypass
F2 Motor protection (overload relay, alternative to ①)
M1 Three-phase motor
Figure 18: Bypass motor control (example)
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