The product standard only contains minimum requirements. Attention is drawn to the fact that appliance specifications might contain requirements additional to or deviating from those specified in the relevant product standards.

Please be aware that the specifications nominal value used in the German part of the Schurter catalogue and the data sheets, is synonymous with rated value.

The difference between these two values is a pure matter of definition. In order to avoid any unnecessary complications we will continue to use the specifications nominal value.

CE marking is the only marking which indicates that a product conforms to the relevant EU-directive.

This means that the CE-mark is no quality or standard conformity mark but only an administration mark.

SCHURTER products are covered by the low voltage directives 72/23/EEC and 93/68/EEC. Those are valid for equipment and appliances with rated voltage values between AC 50 V to AC 1000 V as well as DC 75 V to DC 1500 V.

The CE marking of SCHURTER parts will be found on the label of the smallest packing unit. On request we will submitt a CE conformity statement for each component. CE conformity statements and approvals can also be retrieved from the internet under www.schurter.com.

National testing institutions are testing according to national and international standards or other generally recognized rules of technology. Their certification/approval-marks confirm the observance of the safety requirements which electric appliances must fulfil.

Approvals

National approvals

In addition to the combined UL/CSA approvals, most of the SCHURTER components are also approved by one of the European certification bodies like VDE (Germany), Electrosuisse (Switzerland) or SEMKO (Sweden). The safety testing of all these European certification bodies are based on the commen European safety standards. With the harmonisation effort in Europe, the different national European certification bodies have lost their importance and SCHURTER has decided to maintain only one European approval (e.g. VDE, SEV or SEMKO) in future. The others will not be renewed once they have expired.

Because UL and CSA are not members of the CENELEC, the standards of UL and CSA are not harmonised yet with the European standards. However, UL and CSA are trying to harmonize their standards with each other. Where possible, SCHURTER will apply for the combined cULus or cURus approval.

Further to development in Asia, SCHURTER has obtained national approvals from China, Japan and Korea.

Information about approvals

SCHURTER products are certified according to EN / IEC standards and carry country specific approvals in Europe.

During the last few years European countries made much effort to reduce their approval marks to one generally accepted mark. The ENEC approval mark replaces (wherever possible) the previous approval mark. The ENEC mark is offered by all national certification bodies that signed for the European certification agreement (CCA)*.

SCHURTER decided to reduce the variety of European approval marks. For new approbations of SCHURTER parts only the ENEC will be mentioned in the future:

Approvals for the US and Canada are according to the UL and CSA standards:

As UL and CSA are not a member of CENELEC these two are not according to the European approval marks. Wherever possible SCHURTER want to acquire the combined cULus approval mark:

Since Aug. 1^st. 2003 the Chinese approval mark is required for a lot of products to import to China. SCHURTER strives to get the approvals for the concerned products. For not testable products we offer an import certificate (free of CCC).

Further information:

http://www.enec.com

Approval Industry Links

* members of ENEC agreement:

Standards IEC 60529; EN 60529 and DIN 40050

Scope

These standards apply to the classification of degrees of protection provided by enclosures for electrical equipment with a rated voltage not exceeding 72.5 kV.

Object

The object of these standards is to give:

a) Definitions for degrees of protection provided by enclosures of electrical equipment as regards:

1. Protection of persons against access to hazardous parts inside the enclosure

2. Protection of the equipment inside the enclosure against ingress of solid foreign objects

3. Protection of the equipment inside the enclosure against harmful effects due to the ingress of water.

b) Designations for these degrees of protection.

c) Requirements for each designation.

d) Tests to be performed to verify that the enclosure meets the requirements of these standards.

Designations

The degree of protection provided by an enclosure is indicated by the IP code.

Elements of the IP code and their meanings

A brief description of the IP code elements is given in the following table.

1. Protection against direct and indirect contact – general terms

The protection against electric shock on electric equipment as well as their components are divided into the following parts:

¹⁾ Accessible, conductive part, which is not conductive normally but which may be conductive due to a failure.

2. Protection against direct contact with live parts e.g. of a fuseholder

The data sheets of the relevant components inform about the taken measures.

3. Protection against indirect contact

Measures for the protection against indirect contact on electrical equipment are defined according to IEC 61140 by the 4 protection classes 0, I, II, III. Each protection class includes two protection measures. Even if one of these measures should fail, no electric shocks will occur.

Fig. 1 Thermal only CBE

Fig. 2 Contact force versus deflection

1) Latch-type mechanism

2) Spring-type mechanism

Thermal circuit breakers for equipment, CBEs, (figure 1), simulate the electrothermal behaviour of the protected components (conductors in wiring, motors, transformers, etc.) by a simple, but very clever device: The thermo-bimetal.

This mechanical element can simulate the heating effect of the current, can transform electric energy into a motion (deflection) and trigger a mechanism to cause automatic interruption of the current which produces these effects.

To use the heat created by the current instead of the magnitude of the current itself offers a great advantage, because heat determines the admissible stress of the insulation and the admissible duration of the various overload conditions encountered in practical applications.

Thermally operated CBEs, therefore, take good care of the surplus energy required for start-up or high-torque operation of motors. They cope well with high inrush spikes which occur in switching power supplies, transformers, tungsten filament lamps, etc. and avoid nuisance tripping due to such transients.

The CBEs of the T-Line use a «latch-type» mechanism. High contact force can be maintained until the unit trips. This prevents electrical «noise» due to contact bounce and reduces the risk of contact welding which may occur with spring type mechanisms (figure 2).

The strong points of thermal CBEs are:

• Good simulation of the thermal behaviour of the protected component

• Capability of coping with start-up and inrush currents

• Suitability for a wide range of frequencies

• Simplicity / reliability

• Favourable price

Thermally operated CBEs are temperature sensitive. This, in most applications, is an advantage because the withstand capacity of the component to be protected is almost always temperature sensitive, too. The variation of the operating characteristics of thermal breakers with ambient temperature is closely matched to the admissible thermal stress of PVC insulations. For other insulations, the matching is not as close but the tendency exists, in principle, in any application where the protective device and the component to be protected are operating in an environment of practically identical ambient air temperature.

Thermal CBEs can, to a certain degree, be adjusted to special requirements concerning the withstand capacity of the protected item.

Their delay time can be influenced in several ways. The task may be achieved by using a different method of heating the bimetal. Figure 3 illustrates two methods.

The most widely used method is the direct heating of a bimetal strip by the internal losses produced by the current passing through the bimetal (example A). Where such losses are insufficient to produce enough heat and to cause sufficient deflection, a heater winding is wrapped around the bimetal strip to obtain the required heat. Since the heat has to pass through an insulation before it reaches the bimetal, a time lag will occur and a delayed action will result (example B).

The typical tripping zone of thermal CBEs is shown by figure 4. It changes with ambient temperature in a similar way as the withstand characteristic of a PVC insulated wire does (figure 5). The possibilities can be extended by using a shunt terminal as shown in figure 6.

The shunt terminal provides a parallel switched circuit to the main current sensing circuit.

Fig. 3a Simulation by bimetals (directly heated)

Fig. 3b Simulation by bimetals (indirectly heated)

Fig. 4 Typical tripping zone

Fig. 5 Range of protection

Fig. 6a Circuit diagrams - standard version

Fig. 6b Circuit diagrams - shunt terminal

General information circuit breakers

Fig. 1 Thermischer CBE

Fig. 2 Contact force versus deflection

1) Latch-type mechanism

2) Spring-type mechanism

Circuit breakers for equipment, CBEs, provide protection against hazards of electricity in equipment. For the TA45-line «Protection» includes the safeguarding against harmful thermal effects of overcurrents and the prevention of accidents caused by electricity.

Overcurrent protection is achieved by the automatic interruption of sustained overcurrents with the help of a thermal release tripping the CBE when the duration of an overcurrent exceeds a predetermined limit. The essential part of such a release is a thermo bimetal (figure 1, figure 6a). This mechanical element can simulate the heating effect of the current, can transform electric energy into a motion (deflection) and trigger a mechanism to cause automatic interruption of the current which produces these effects.

To use the heat created by the current instead of the magnitude of the current itself offers a great advantage, because heat determines the admissible stress of the insulation and the admissible duration of the various overload conditions encountered in practical applications. Thermally operated CBEs, therefore, take good care of the surplus energy required for start-up or high-torque operation of motors. They cope well with high inrush spikes which occur in switching power supplies, transformers, tungsten filament lamps, etc. and avoid nuisance tripping due to such transients.

Bimetals can also handle frequencies in a fairly wide range, e.g. from DC to 400 Hz, without necessitating any change in ratings or characteristics. The CBEs of the TA45-line use a «latch-type» thermal release. High contact force can be maintained until the unit trips. This prevents electrical «noise» due to contact bounce and reduces the risk of contact welding which may occur with spring type mechanisms (figure 2).

Thermally operated CBEs are temperature sensitive. This, in most applications, is an advantage because the withstand capacity of the component to be protected is almost always temperature sensitive too.

Thermal magnetic CBEs have two releases to achieve automatic interruption of an overcurrent (figure 7):

1) A thermo-bimetal for overload current

2) An electro magnet for short circuit current

Consequently, the operating characteristic is essentially composed of two zones, linked by a zone (3) where either one or the other mode of tripping will be effective (figure 8).

The electro magnet should be dimensioned so that it will not trip during transients likely to occur in the intended application. This determines the level of the current below which instantaneous tripping should not occur.

The upper level, indicating the current above which instantaneous tripping must occur, is of interest in considerations concerning the selective action of two protective devices.

In the short circuit range of overcurrents (above 8....12 times the rated current), the faster interruption obtainable with the magnetic release is an advantage. It can help to save the heater windings of indirectly heated bimetals from overheating and it can improve the breaking capacity of the CBE. The CBEs primarily intended for overload protection are usually capable of interrupting, without back-up assistance, currents up to 100 to 300 amps and be fit for further use after such an interruption. The performance at higher fault levels usually relies on back-up assistance by fuses or breakers.

Fig. 7 Thermal-magnetic CBE

1) Thermo-bimetal

2) Electro magnet

Fig. 8 Tripping zones of thermal magnetic CBEs

1) Thermal mode of tripping

2) Magnetic mode of tripping

3) Either thermal or magnetic mode

The prevention of accidents can be achieved in several ways. To safeguard persons from the possible risks of injuries arising from an unexpected restarting of an electric motor when the voltage recovers after a power failure, undervoltage releases can be fitted to the basic CBE. This release will trip the CBE when the voltage drops below a certain level. The restarting requires a manual ON operation.

Fig. 3 Undervoltage release

Fig. 4 Mechanical lock-out latch

Undervoltage releases can be combined with overcurrent releases in one integral unit. The TA45-line utilizes a special version of an undervoltage release as illustrated by figure 3. It differs from the conventional version by using an additional latch, reducing the anlatching force significantly. The release can thus be operated with far less power and utilize rectified AC to avoid any humm while the CBE is in the ON position. The wiring diagram is shown by figure 6b. Typical examples for the use of undervoltage releases are floor cleaning machines, high pressure cleaning equipment etc.

To prevent injuries caused by dangerously exposed moving parts of a machine, a mechanical lock-out latch can be fitted to the basic CBE. A spring loaded pin will cause the CBE to trip when a protective cover is removed from dangerous parts, like the cutting knifes of a shredder. The CBE can not be switched ON as long as the protective cover is not in its place. Figure 4 shows the operating principle. Figure 6c shows the wiring diagram.

Protection may also be necessary when at a remote location a dangerous situation occurs which could escalate if the CBE did not interrupt the current. To avoid such a risk, a remote trip release ca be fitted to the basic CBE to achieve tripping on sensor command. The operating principle is shown by figure 5, the working diagram by figure 6d.

Fig. 5 Remote trip release

The various possibilities of combining different protective functions is also reflected by the wiring diagrams as shown in figure 6.

• Fig. 6a shows the wiring diagram fo the basic CBE, with one protected pole. The TA45 can be outfitted with two protected poles for additional safety against faults to earth.

• Fig. 6e shows the more complex diagram, utilizing a shunt connection (P1-5) and a change over auxiliary contact.

• The wiring diagrams for CBEs with an undervoltage release, a mechanical lock-out latch and a remote trip release are shown by 6b, d, and c.

CBEs of the TA45-line are available with rocker or push button actuators and protective covers to obtain the desired degree of protection.

The strong points of the TA45-line are:

• Thermal overload protection

• Undervoltage release

• Remote trip release

• Mechanical lock-out latch

• 3 pole version

• Rocker actuation

• Push button actuation

• Auxiliary contact.

• Shunt terminal

Special features:

• Good simulation of the thermal behaviour of the protected component

• Capability of coping with start-up and inrush currents

• Suitability for a wide range of frequencies

• Simplicity / reliability

• Favourable price

• Approvals