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Locking

The S 750 (DR) is provided with an integrated locking tab which

makes it possible to block the all poles simultaneously. The

integrated locking tab locks the circuit-breaker in ON or

OFF position and can be additionally protected by a pad

lock, wire seal or cable tie. When locked in ON position, the

protective function is maintained in case of a fault: The

blocked switch handle still permits the tripping of the me

chanism and opening of the contacts in case of overload

or short-circuit (trip-free mechanism). The indicator shows

“green” also in case of a fault with ON position locked –

giving you the certainty that power is switched off.

Furthermore ABB offers the auxiliary contact for

the S 750 DR range. S 750 DR-AUX is a two

change-over contact that indicates the contact

position of the S 750 DR pole(s) independently

and potential-free. This helps to easily monitor individual circuits

Function

Selective Main Circuit-Breaker series S 750 DR

ABB’s S 750 DR is used as a reliable group protec

tion device worldwide. S 750 DR is the right

choice when it comes to selectivity for critical

power application such as hospitals, airports and

data center. But also in residential application

SMCB technology has big advantages. In Germany

SMCB technology became the standard choice for

meter board application where the products

works as a group protection device for down stream circuits.

In order to avoid unauthorized manual switching

the S 750 DR. The S 750 DR is provided with an

integrated locking tab which makes it possible to

block the all poles simultaneously. 

The integrated locking tab locks the circuit-breaker in ON or OFF

position and can be additionally protected by a

padlock, wire seal or cable tie. When locked in ON

position, the protective function is maintained in

case of a fault: The blocked switch handle still

permits the tripping of the mechanism and open

ing of the contacts in case of overload or

short-circuit (trip-free mechanism). The indicator

shows “green” also in case of a fault with ON po

sition locked – giving you the certainty that power

is switched off.

Function

ABB SMCB operate according to a voltage-independent principle.

They do not require an auxiliary source, neither for making /

breaking contact nor for the protective function. For overload

tripping, a thermostatic bimetal is used. As usual for circuit-

breakers, it is necessary to separate the main contacts in a time

less than 1ms by using a short-circuit “hammer trip” solenoid to

ensure effective short-circuit limitation. When the downstream

protection device has tripped because of a short-circuit, the

contact tips reclose automatically through a simple spring-type

system without requiring auxiliary energy.

If a short-circuit occurs between the S 750 (DR) and the

downstream circuit-breaker, another bimetal release enables

short-time delayed tripping. Both the selective release and the

overload release trip the mechanism and ensure that the contact

tips remain in the open position enabling isolating. The current

is limited and the arc is quenched as in the case of standard

circuit-breakers by means of quick contact opening by a “ham

mer trip” solenoid and quick build-up of the arc voltage in the

quenching chamber.

Purpose

– Ensure power supply capability over a large temperature range

– Protect wires and cables in case of operational overload or short-circuit

– Additional limitation of let-through current and let-through

energy in case of short-circuit tripping in final circuit

– Disconnection and isolation of the system, also by ordinary people

– Special selectivity with respect to downstream circuit

breakers and upstream fuses

– Ensure a high availability of the electrical power supply

If a short-circuit occurs between the S 750 (DR) and the

downstream circuit-breaker, another bimetal release enables

short-time delayed tripping. Both the selective release and the

overload release trip the mechanism and ensure that the contact

tips remain in the open position enabling isolating. The current

is limited and the arc is quenched as in the case of standard

circuit-breakers by means of quick contact opening by a “ham

mer trip” solenoid and quick build-up of the arc voltage in the

quenching chamber.

This operating principle achieves a particularly high selective behaviour

– the current-limiting selectivity.

In case of short-circuit in final circuits, the S 750 (DR) supports the downstream

circuit breaker and limits the energy and thus minimizes the im

pact on the whole installation and the feeding supply network.

This selective behaviour of the S 750 (DR) offers major advanta

ges compared to fuse-based technologies.

 Two mounting variants are available: S 750 for bus bars and S 750 DR for DIN rail mounting.

– High short-circuit breaking capability of 25 kA over the complete rated current range

– High energy-limiting capacity by current-limiting selectivity

– Suitable for selective overcurrent protection at the meter

mounting board and in general-purpose electric main distribution boards

– Suitable to disconnect and isolate electric circuits

– Voltage-independent function (no connection to neutral)

– Applicable in installation acc. to:

Overvoltage category I … IV,pollution degree 1 … 3

– S 750 DR version for DIN rail mounting

– S 750 version for mounting on busbar systems without

using any tools, with screwless connection on load side

and additional cage terminals for the supply to the busbar system

– Isolation function according to IEC 60364-5-53

– Additional contact position indicator

RED = ON ; GREEN = OFF

– Lockable and sealable

– For operation by ordinary people

2CDC 021 205 F0007

Fields of application

– As isolating device in meter boards for downstream

customer´s installation

2CDC 021 007 S0011

– In main distribution boards or switchgear as a selective

group or back-up protection device, especially where a

high degree of continuity of supply is required, e.g. for

installations related to “Safety Services” (IEC 60346-5-56),

“Medical Locations” (IEC 60364-7-710) etc.

– For general applications with tripping characteristic E

– For the protection of areas where high current peaks

(e.g. start-up currents) occur during operation, using

circuit-breakers with tripping characteristic K (S 750 DR)

Selective main circuit-breakers of the S 750 and S 750 DR series are SMCBs

according to DIN VDE 0641-21 with voltage-independent Operating principle.

This means that they do not rely on a control circuit to make or break contact

(SHU) and are therefore particularly suitable for use in energy distribution

systems with maximum availability requirements. Two mounting variants

are available: S 750 for bus bars and S 750 DR for DIN rail mounting.

For overload tripping, a thermostatic bimetal is used,

as in the case of a standard circuit-breaker.

And also as for circuit-breakers, it is necessary to separate

main contacts quickly by using a short-circuit “hammer trip”

solenoid to ensure effective short-circuit limitation. When the

downstream protective device has tripped because of a short

circuit, the contact tips reclose again. This occurs without

auxiliary energy through a simple spring-type system.

If a short circuit occurs between the S 750 and the down

stream mcb, another bimetal release enables the short-time

delay tripping. Both the selective release and the overload

release trip the mechanism and ensure that contact tips

remain in the open position to comply with isolation require ments.

The current is limited and the arc is quenched as in the case

of circuit-breakers.

The underlying switching principle enables a special selectivity

behaviour: current-limiting selectivity. When a short circuit

occurs, the S 750 supports the downstream mcb and also

limits the energy that has an impact on the installation and –

subsequently – on the network of the supplier. The selectivity

behaviour of the S 750 offers major advantages compared to

fuse-based technologies.

Function

STOTZ selective main circuit breakers operate voltage

independent. They do not require auxiliary energy for swit

ching the device on or off or for their protection functions.

A straight forward design ensures the reliable protection

function. The functional elements consist of proven electro

mechanical components specifically designed for these

requirements.

The underlying switching principle enables a special selectivity

behaviour: current-limiting selectivity. When a short circuit

occurs, the S 750 supports the downstream mcb and also

limits the energy that has an impact on the installation and –

subsequently – on the network of the supplier. The selectivity

behaviour of the S 750 offers major advantages compared to

fuse-based technologies.

Special features of the

selective main circuit-breaker S 750

− High breaking capacity 25 kA at 230/400 V~

− High energy limitation

− Suitable to provide selective overcurrent protection

in meter boards and in main distribution frames

− Suitable for isolation of electric circuits

− Current-limiting selectivity

− Voltage independent function

− High isolation ability:

Ui = 690 V,

Uimp = 6 kV with a test voltage of 9.8 kV

Overvoltage category IV,

Pollution degree 3

− Easy assembly with screwless connection to busbars

and cables on the load side

− Input frame terminals for busbar feeding

up to 50 mm2/100 A

− Isolation function according to IEC 60364 and IEC 60664

− Additional contact position indicator

RED = ON / GREEN = OFF

− Lockable and sealable

− Can be operated by ordinary people

STOTZ selective main circuit breakers fully comply with

the requirements of the German utilities directive (Technical

Connection Requirements of Network Operators) concerning

the mandatory pre-meter isolation and protection functions.

For these applications, selective main circuit breakers:

− ensure load current carrying capability over a large

temperature range;

− protect cables in the case of functional overload;

− protect cables in the case of a short circuit;

− clear high short-circuit currents reliable;

− limit the let-through current and let-through energy also

in the case of selective short-circuit disconnection by

downstream mcb

− provide disconnection and re-connection of installation,

also by ordinary people;

− provide selectivity with respect to downstream

circuit-breakers and upstream fuses;

− ensure highest availibility of electrical power supply for the customer.