Lenze 8200 Frequency inverters - Manual (Page 250)

Network of several drives
8200SHB0199 10-7
10.2.5 Protection in networks of several drives
You have the possibility of selecting a graded protection concept for network
operation. The damage risk depends on the type of protection. The following table
helps to analyse the risk.
Please note:
-
The rating of the cable cross-section of the common DC-bus must be
appropriate for the sum of parallel mains supplies:
- The sum of the rated fuse currents is the rated value for the cross-section
of the busbars.
- Observe the local standards and regulations.
-
On the motor side, the cable protection is supported by the current
limitation of the controller. Condition:
- The current limit set for the controller corresponds to the rated current of
the connected motor.
- For group drives, additional protection of the single drives is
required/recommended.
Definition: ”internal fault”
-
Controllers:
- The fault is located between the connection point at the DC-bus and
inside the unit in front of the terminals U, V, W.
-
Supply modules:
- The fault is located between the mains input (terminals L1, L2, L3) and the
farthest point of the DC-bus.
Protection by F1 ... F3
Protection of Cable protection
- on the mains side
- on the DC-bus
- on the motor side
No unit protection
Possible faults One or more controllers with
- internal short circuit (+ U
G→
-U
G
)
- internal earth fault (+ U
G→
PE/-U
G→
PE)
- motor-side earth fault on phase W
Mains failure of a controller with
decentral supply.
Risk Several parallel controllers supply the fault location(s) via the
DC-bus. This may lead to overload of the intact controller, as the
faulty controller is not selectively activated on the DC-bus.
- Possible damage with central and decentral supply
- destruction of the controller concerned
- destruction of the controllers still intact
- destruction of the supply unit
If a mains-side supply/input fails
because F1 ... F3 blows, the active
controller which is connected can be
overloaded.
Note The extent of destructions depends on the ratio ”DC-bus power of the whole system / rated power of the
controller concerned”.
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