A major feature of withdrawable-unit design is removability and ease of replace-ment of equipreplace-ment combinations under operating conditions, i.e. a switchboard can be adapted to process-related modifi-cations without having to be shut down.
Withdrawable-unit design is used therefore mainly for switching and control of motors (Fig. 8).
Withdrawable units
The equipment of the main circuit of an outgoing feeder and the relevant auxiliary equipment are integrated as a function unit in a withdrawable unit, which can be easily accommodated in a cubicle.
In basic state, all equipment and movable parts are within the withdrawable unit con-tours and thereby protected from damage.
The facility for equipping the withdrawable units from the rear allows plenty of space for auxiliary devices. Measuring instru-ments, indicator lights, pushbuttons, etc.
are located on a hinged instrument panel, such that settings (e.g. on the overload relay) can be easily performed during operation.
Fig. 8: High packing density with up to 40 feeders per cubicle
Fig. 9: SIVACON withdrawable units size 1, size 1/4 and 1/2 A distinction is made between miniature (sizes 1/4 and 1/2) and normal withdraw-able units (sizes 1, 2, 3 and 4) (Fig. 9).
The normal withdrawable unit of size 1 has a height of one modular spacing (175 mm) and can, with the use of a mini-ature withdrawable unit adapter, be re-placed by 4 withdrawable units of size 1/4 or 2 units of size 1/2. The withdrawable units of sizes 2, 3 and 4 have a height of 2, 3 and 4 modular spacings, respectively.
The maximum complement of a cubicle is, for example, 10 full-size withdrawable units of size 1 or 40 miniature withdrawa-ble units of size 1/4 .
1
2
3
4
5
6
7
8
9
10
Fig. 10: Withdrawable-unit principle
Moving isolating contact system For main and auxiliary circuits the with-drawable units are equipped with a moving isolating contact system. It has contacts on both the incoming and outgoing side;
they can be moved by handcrank such that they come laterally out of the withdrawa-ble unit and engage with the fixed contacts in the cubicle. On miniature withdrawable units the isolating contact system moves upwards into the miniature withdrawable unit adapter.
A distinction is made between connected, disconnected and test position (Fig. 10).
In the connected position both main and auxiliary contacts are closed; in the discon-nected position they are open. The test position allows testing of the withdrawable unit for proper function in no-load (cold) state, in which the main contacts are open, but the auxiliary contacts are closed for the incoming control voltage.
In all three positions the doors are closed and the withdrawable unit mechanically connected with the switchboard.
This assures optimal safety for personnel and the degree of protection is upheld.
Movement from the connected into the test position and vice-versa always passes through the disconnected position; this assures that all contactors drop out.
Operating error protection Integrated maloperation protection in each withdrawable unit reliably prevents moving of the isolating contacts with the main circuit-breaker ”CLOSED“ (handcrank cannot be attached) (Fig. 11).
Fig. 11: Operating error protection prevents travel of the isolating contacts when the master switch is “ON”
Connected position
Disconnected position
Test position L3
L2 L1 N
L3 L2 L1 N
L3 L2 L1 N
1
2
3
4
5
6
7
8
9
10
Low-Voltage Switchboards
Indicating and signaling
The current position of a withdrawable unit is clearly indicated on the instrument panel. Such signals as ”feeder not avail-able“ (AZNV), ”test“ and ”AZNV and test“
can be given by additional alarm switches.
The alarm switch in the compartment (S21) is a limit switch of NC design; that in the withdrawable unit (S20) is of NO design. Both are actuated by the main isolating contacts of the withdrawable unit (Fig. 12).
Fig. 12: Circuitry and position of main and auxiliary contacts X19 = Auxiliary isolating contact
S20 = Alarm switch in withdrawable unit*
S21 = Alarm switch in compartment*
WU = Withdrawable unit Compt. = Compartment
*actuated by main isolating contact Test
AZNV AZNV/Test
*No signal, as auxiliary isolating contact open
* Main isolating
contact
Aux. isolating contact
In with-drawable unit - S 20 1 NO
In compartment - S 21
1 NC
Connected
Disconnected
Test
Compt.
WU WU Compt. WU Compt.
- X19
- Q1 - S21
21
22
- S21
22 COM
AZNV Test - X19
- Q1 - S21 - S20
21
22 21
- X19
1
2
3
4
5
6
7
8
9
10
Fig. 13: Arcing fault-protected plug-on bar system embedded in the left of the cubicle
Vertical distribution bus (plug-on bus) The vertical plug-on bus with the phase conductors L1, L2 and L3 is located on the left-hand side of the cubicle and features safe-to-touch tap openings (Fig. 13).
The vertical PE, PEN and N busbars are on the right-hand side of the cubicle in a separate, 400 mm wide cable connection compartment, equipped with variable cable brackets.
Rated currents – fused and withdraw-able unit sizes of cwithdraw-able feeders
Rated currents – non-fused and with-drawable unit sizes of cable feeders
Fig. 14
I
D306 3KL50 3KL52 3KL53 3KL55 3KL57 3KL61
35 63 125 160 250 400 630
1/4 / 1/2 1 1 2 2 2 3
Device Rated
current
With-drawable unit size
Type [A]
Device
3RV101 3RV102 3RV103 3RV104 3VF3 3VF4 3VF5 3VF6
12 25 50 160 160 250 400 630
1/4 / 1/2 1/4 / 1/2 / 1 1/2 / 1 1 1 2 2 4 Rated
current
With-drawable unit size
Type [A]
1
Low-Voltage Switchboards
Power ratings – fused and withdraw-able unit sizes of motor feeders
Fig. 15
FVNR FVR Star-delta starters
400 V 500 V 690 V 400 V 500 V 690 V 400 V 500 V 690 V 400 V 500 V 690 V Full-voltage
non-reversing (FVNR) motor starters Normal-duty start [kW]
Full-voltage non-reversing (FVNR) motor starters Heavy-duty start [kW]
Full-voltage reversing (FVR) motor starters Reversing circuit [kW]
Star-delta starters [kW]
Withdrawable unit size
–
1
FVNR FVR Star-delta starters
I I
Withdrawable unit size
–
non-reversing (FVNR) motor starters Normal-duty start [kW]
Full-voltage non-reversing (FVNR) motor starters Heavy-duty start [kW]
Full-voltage reversing (FVR) motor starters Reversing circuit [kW]
Star-delta starters [kW] unit size
11
non-reversing (FVNR) motor starters Normal-duty start [kW]
Full-voltage non-reversing (FVNR) motor starters Heavy-duty start [kW]
Full-voltage reversing (FVR) motor starters Reversing circuit [kW]
Star-delta starters [kW]
Power ratings – non-fused with
overload relay and withdrawable unit sizes of motor feeders
Coordination type 1
Coordination type 2
Fig. 16
1
2
3
4
5
6
7
8
9
10
Low-Voltage Switchboards
I I
FVNR FVR
Full-voltage non-reversing (FVNR) motor starters
Normal-duty start [kW]
Coordination type 1
Coordination type 2
Full-voltage reversing (FVR) motor starters
Reversing circuit [kW]
Full-voltage non-reversing (FVNR) motor starters
Normal-duty start [kW]
Full-voltage reversing (FVR) motor starters
Reversing circuit [kW]
Modulheight [mm]
400 V 11 45 –
400 V – 11 45
400 V 7.5 45 –
400 V – 7.5 45
50 100 200 Modulheight [mm]
50 100 200