CEI EN 60947-4-3

This part of IEC 60947 applies to a.c. semiconductor non-motor
load controllers and contactors intended for performing electrical
operations by changing the state of a.c. electric circuits between
the ON-state and the OFF-state. Typical applications are classified
by utilization categories given in Table 2.

As controllers, they may be used to reduce the amplitude of the
r.m.s. a.c. voltage on the load terminals from that of the applied
voltage – either continuously or for a specified period of time.
The half-wave period of the a.c. wave form remains unchanged from
that of the applied voltage.

They may include a series mechanical switching device and are
intended to be connected to circuits, the rated voltage of which
does not exceed 1 000 V a.c.

This standard characterizes controllers and contactors for use
with or without bypass switching devices.

The semiconductor controllers and contactors dealt with in this
standard are not normally intended to interrupt short-circuit
currents. Therefore, suitable short-circuit protection (see 8.2.5)
should form part of the installation but not necessarily of the
controller itself.

In this context, this standard gives requirements for
semiconductor controllers and contactors associated with separate
short-circuit protective devices.

This standard does not apply to:

− operation of a.c. and d.c. motors;

− low-voltage a.c. semiconductor motor controllers and starters
covered by IEC 60947-4-2;

− electronic a.c. power controllers covered by the IEC 60146
series;

− all-or-nothing solid-state relays.

Contactors and control-circuit devices used in semiconductor
controllers and contactors should comply with the requirements of
their relevant product standard. Where mechanical switching devices
are used, they should meet the requirements of their own IEC
product standard and the additional requirements of this
standard.

The object of this standard is to state

a) the characteristics of semiconductor controllers and
contactors and associated equipment;

b) the conditions with which semiconductor controllers and
contactors should comply with reference to:

− their operation and behaviour;

− their dielectric properties;

− the degrees of protection provided by their enclosures, where
applicable;

− their construction;

c) the tests intended for confirming that these conditions have
been met, and the methods to be adopted for these tests;

d) the information to be given with the equipment or in the
manufacturer's literature.