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IEC 60947-4-1 Document Information:
Title
Low-voltage switchgear and controlgear – Part 4-1: Contactors and motor-starters – Electromechanical contactors and motor-starters
Appareillage à basse tension – Partie 4-1: Contacteurs et démarreurs de moteurs – Contacteurs et démarreurs électromécaniques
International Electrotechnical Commission
Publication Date:
Sep 1, 2009
Scope:
Scope and object
This part of IEC 60947 applies to the types of equipment listed in 1.1
and 1.2 whose main contacts
are intended to be connected to circuits the rated voltage of which
does not exceed 1 000 V a.c. or
1 500 V d.c.
Starters and/or contactors dealt with in this standard are not
normally designed to interrupt
short-circuit currents. Therefore, suitable short-circuit protection
(see 9.3.4) shall form part of
the installation but not necessarily of the contactor or the starter.
In this context, this standard gives requirements for:
- contactors associated with overload and/or short-circuit protective
devices;
- starters associated with separate short-circuit protective devices
and/or with separate
short-circuit and integrated overload protective devices;
- contactors or starters combined, under specified conditions, with
their own short-circuit
protective devices. Such combinations, e.g. combination starters (see
3.2.7) or protected starters
(see 3.2.8) are rated as units.
Circuit-breakers and fuse-combination units used as short-circuit
protective devices in combination
starters and in protected starters shall comply with the requirements
of IEC 60947-2 and IEC
60947-3, as the case may be.
Equipment covered by this standard is as follows.
AC and d.c. contactors
AC and d.c. contactors intended for closing and opening electric
circuits and, if combined with
suitable relays (see 1.2), for protecting these circuits against
operating overloads which may
occur therein.
NOTE Contactors combined with suitable relays and which are intended
to provide short-circuit
protection shall additionally satisfy the relevant conditions
specified for circuit-breakers (IEC
60947-2).
This standard applies also to the actuators of contactor relays and to
the contacts dedicated
exclusively to the coil circuit of a contactor.
Contactors or starters with an electronically controlled electromagnet
are also covered by this
standard.
AC motor-starters
AC motor-starters intended to start and accelerate motors to normal
speed, to ensure continuous
operation of motors, to switch off the supply from the motor and to
provide means for the
protection of motors and associated circuits against operating
overloads.
Starters the operation of which depends on thermal electrical relays
for motor protection complying
with IEC 60255-8, or motor-incorporated thermal protective devices
dealt with in IEC 60034-11 do
not necessarily meet all the relevant requirements of this standard.
Overload relays for starters, including those based on solid state
technology, shall meet the
requirements of this standard.
Direct-on-line (full voltage) a.c. starters
Direct-on-line starters intended to start and accelerate a motor to
normal speed, to provide means
for the protection of the motor and its associated circuits against
operating overloads, and to
switch off the supply from the motor.
This standard applies also to reversing starters.
Reduced voltage a.c. starters
Reduced voltage a.c. starters intended to start and accelerate a motor
to normal speed by
connecting the line voltage across the motor terminals in more than
one step or by gradually
increasing the voltage applied to the terminals, to provide means for
the protection of the motor
and its associated circuits against operating overloads, and to switch
off the supply from the
motor.
Automatic change-over devices may be used to control the successive
switching operations from one
step to the others. Such automatic change-over devices are, for
example, time-delay contactor
relays or specified time all-or-nothing relays, under-current devices
and automatic acceleration
control devices (see 5.10).
Star-delta starters
Star-delta starters intended to start a three-phase motor in the star
connection, to ensure
continuous operation in the delta connection, to provide means for the
protection of the motor and
its associated circuits against operating overloads, and to switch off
the supply from the motor.
The star-delta starters dealt with in this standard are not intended
for reversing motors rapidly
and, therefore, utilization category AC-4 does not apply.
NOTE In the star connection, the current in the line and the torque of
the motor are about
one-third of the corresponding values for delta connection. Therefore,
star-delta starters are used
when the inrush current due to the starting is to be limited, or when
the driven machine requires a
limited torque for starting. Figure 1 indicates typical curves of
starting current, of starting
torque of the motor and of torque of the driven machine.
Two-step auto-transformer starters
Two-step auto-transformer starters, intended to start and accelerate
an a.c. induction motor from
rest with reduced torque to normal speed and to provide means for the
protection of the motor and
its associated circuits against operating overloads, and to switch off
the supply from the motor.
This standard applies to auto-transformers which are part of the
starter or which constitute a unit
specially designed to be associated with the starter.
Auto-transformer starters with more than two steps are not covered by
this standard.
The auto-transformer starters dealt with in this standard are not
intended for inching duty or
reversing motors rapidly and, therefore, utilization category AC-4
does not apply.
NOTE In the starting position, the current in the line and the torque
of the motor related to the
motor starting with rated voltage are reduced approximately as the
square of the ratio (starting
voltage):(rated voltage). Therefore, auto-transformer starters are
used when the inrush current due
to the starting is to be limited or when the driven machine requires a
limited torque for starting.
Figure 2 indicates typical curves of starting current, of starting
torque of the motor and of
torque of the driven machine.
Rheostatic rotor starters
Starters intended to start an a.c. induction motor having a wound
rotor by cutting out resistors
previously inserted in the rotor circuit, to provide means for the
protection of the motor against
operating overloads and to switch off the supply from the motor.
In the case of asynchronous slip-ring motors (wound-rotors), the
highest voltage between open
slip-rings shall be not greater than twice the rated insulation
voltage of the switching devices
inserted in the rotor circuit (see 5.3.1.1.2).
NOTE This requirement is based on the fact that the electric stresses
are less severe in the rotor
than in the stator and are of short duration.
This standard applies also to starters for two directions of rotation
when reversal of connections
is made with the motor stopped (see 5.3.5.5). Operations including
inching and plugging necessitate
additional requirements and shall be subject to agreement between
manufacturer and user.
This standard applies to resistors which are part of the starter or
constitute a unit specially
designed to be associated with the starter.
This standard does not apply to:
- d.c. starters;
- star-delta starters, rheostatic rotor starters, two-step
auto-transformer starters intended for
special applications and designed for continuous operation in the
starting position;
- unbalanced rheostatic rotor starters, i.e. where the resistances do
not have the same value in
all phases;
- equipment designed not only for starting, but also for adjustment of
speed; liquid starters and
those of the "liquid-vapour" type;
- semiconductor contactors and starters making use of semiconductor
contactors in the main circuit;
rheostatic stator starters;
contactors or starters designed for special applications;
auxiliary contacts of contactors and contacts of contactor relays.
These are dealt with in IEC
60947-5-1.
The object of this standard is to state:
a) the characteristics of contactors and starters and associated
equipment;
b) the conditions with which contactors or starters shall comply with
reference to:
1) their operation and behaviour,
2) their dielectric properties,
3) the degrees of protection provided by their enclosures, where
applicable,
4) 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.
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