An Introduction to E-T-A Circuit Protection
E-T-A Catalogue
Interrupting Capacity Icn
Overload and maximum interrupting capacities are specified for each
series, defined as the maximum current levels that can be switched
safely for a minimum of 40 operations, and a minimum of 3 operations
respectively. Forthermalcircuitbreakersback-upprotectionisadvised
if higher currents are possible. Please contact us for further advice on
specific applications.
The E-T-A catalogue describes the largest product range of its type,
providing solutions to almost any requirement. It is divided into the
following sections:
Introduction
Thermal circuit breakers
0
IEC934/EN60934definesinterruptingcapacityastheratedconditional
short circuit current performance. According to category PC1, this is
thevalueofratedconditionalshortcircuitcurrent(interruptingcapacity)
for which the prescribed conditions do not include fitness of the CBE
for its further use. PC2 is defined as the value of rated conditional short
circuit current for which the prescribed conditions do include fitness of
the CBE for its further use.
Thermal-magnetic circuit breakers
Hydraulic-magnetic and magnetic circuit breakers
High performance circuit breakers and battery switches
Door lock, time delay and motor protection controls
Solid State Remote Power Controllers (SSRPCs)
Electronic products
Approvals
Each product section includes a quick selector chart and short form
presentation of the range, followed by detailed specifications for
individual product types or groups.
Switching Sequence
The switching sequence for short circuit tests is normally abbreviated
as follows, according to relevant international CBE standards.
o: Break operation (open)
Please contact us if you have any difficulty in matching a product to
your requirements or have a special application - we have the flexibility
to develop custom solutions tailored to specific needs: products that
are both solution-oriented and cost effective.
The circuit breaker in the closed position is caused to open
through a short circuit current applied by means of a separate
switch. Referenced as co (closed open) in earlier specifications.
co: Make operation with subsequent break operation (close open)
The circuit breaker in the open condition is closed onto a sustained
short circuit and must immediately re-open. This operating mode
requires the circuit breaker to be fail-safe as the actuator cannot
be released as quickly as the circuit breaker mechanism will open.
Referenced as oco (open close open) in earlier specifications.
t: Time period between switching operations
A separate catalogue fully describes E-T-A electronic sensors, control
products and instrumentation.
Normally 3 minutes, or the period required before the circuit
breaker can be re-set.
E-T-A Choice –
Circuit Breakers to Ensure the Best Protection
Solderability of Silver-Plated Terminals
E-T-A products with silver-plated terminals will not be adversely affected
(e.g. by sulphur induced corrosion) by the packaging material. However,
the solderability of silver-plated terminals can deteriorate with time.
Provided these products are stored, solderability will be guaranteed for a
period of six months from the date of delivery. If they are not required
immediately, it is recommended that these products are packed and
stored in polythene bags. No drying agents should be used as they may
contain silicate gel which can impair solderability. Flux should be non-
halogenous.
A number of factors arise in choosing a circuit breaker to protect
against overloads and short circuits. E-T-A specialists can advise on
your requirement, according to the specific field application.
Four types of tripping operation cover most situations.
1.Thermal Circuit Breakers (TO)
Thetrippingmechanismcomprisesathermalactuatorandmechanical
latch, designed to discriminate between in-rush/temporary current
surges and prolonged overloads to ensure effective overcurrent
protection. Applications include motors, transformers, solenoids
and low voltage wiring.
E-T-A Advantages
Snap-Action Mechanism
The snap-action mechanism featured in many E-T-A models ensures
that the contact closing speed is independent of the speed of operation
of the actuator (push button, rocker, toggle etc.). The moving contact
is retained until the actuator causes a defined force to act in the closing
direction of the contacts. Once this force is exceeded, the mechanical
retention is overcome allowing the contacts to snap closed (tease free
mechanism.) The closing speed is a function of this force alone.
Snap-action mechanisms eliminate contact welding upon switching on
to sustained short-circuits and minimise the risk of contact wear over
the circuit breakers’ life.
2. Thermal-Magnetic Circuit Breakers (TM)
Combining a solenoid in series with a bimetal thermal actuator, these
provide time current characteristics with two distinct steps. A high
overcurrent value causes the solenoid to trigger the release
mechanism rapidly, the thermal mechanism responds to prolonged
low value overloads. These circuit breakers are well suited to
telecommunications, process control, and similar applications
requiring precision performance.
3. Magnetic Circuit breakers (MO or HM)
A well-proven design of solenoid coil with optional hydraulic delay
provides tripping that is highly tolerant of changes in ambient
temperature. Awiderangeofperformancecharacteristicsisavailable
in single, double and three pole configurations.
Trip Free Mechanism
Series 808 and 809 are fast acting magnetic devices sensitive to
small overload currents. Typical applications include printed circuit
board and power semi-conductor protection.
4. High Performance Circuit Breakers
Where ultimate operation under adverse conditions is required,
E-T-A high performance circuit breakers provide high interrupting
capacity and excellent environmental specifications. Available in
thermal and thermal-magnetic versions, they offer current ratings up
to 500 A. Special models are designed for aerospace, defence and
similar heavy-duty applications.
R
E-T-A circuit breakers cannot be held closed against an overload. This
is achieved through the use of positively trip free designs in accordance
with IEC 934/EN 60934 (with the exception of models 1610, 1658, 808
and 809 which are designed for specialised applications).
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Germany (0 91 87) 10-0 - USA (847) 827-7600 - UK (01296) 420336 - www.etacbe.com
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