Eaton Industrial Switchgear - General Information

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2010 CA08103002Z-EN
22/12 Switchgear for North America
the main switch can be switched on
only when all control panel doors are
closed and that all doors are mechani-
cally and/or electrically interlocked
with the switch that the doors can not
be opened when the main switch is
closed1).
A simple interlock with a shunt release
that simply trips the main switch when
a door is opened should be avoided, as
this can lead to critical or dangerous
situations for plant and personnel2).
A defeat mechanism, with which
specialists can temporarily disable the
door interlock to correct faults is
permissible3), as faults can often be
determined only in a live system. If
more comprehensive measures are
required to rectify faults, the plant
should be shut down for the duration of
the work.
To ensure the permanent connection
between operating elements and
switches, main switches with handle
mechanisms are the preferred choice.
The switch handles are fitted directly
to the sides of the switches or more
flexibly connected with a bowden
cable. The fronts of North American
control panels typically feature a fixed
flange over the panel’s entire height,
into which the handle is installed, so
that they can also be operated when
the panel door is open. These handles
are referred to an flange-mounted
handle4) in North America. These
handles are, in addition, connected to
all control panel doors with a mechan-
ical interlock. Eaton supplies these
handles5) with a standard drilling
template and with bowden cables of
various lengths – see page 17/xx.
Lever handles do not fulfil the require-
ments of IEC/EN standards and do not
contain the CE mark. They must there-
fore be used only in North America.
Panel builders working to IEC/EN stan-
dards normally use these operating
elements and the special control
panels only by customer request.
In distribution equipment switches
with toggle lever mechanisms are
often used, while in industrial control
panels6) switches with rotary
mechanisms are preferred. For main
switches, door coupling rotary
handles with a high protection type are
usually used, since these must be
operable when the control panel door
is closed. With the panel door open,
the handle is on the outside of the door
so that the switch can not be operated
without tools. An additional handle7)
can therefore be fitted to the switch
axis inside the panel. According to the
standards, this handle must be oper-
able only through deliberate action8).
To fulfil this requirement, Eaton’s
handles must, with the panel door
opened, be rotated through about
15 degrees, then pushed and at the
same time turned further to close the
switch. Switching off does not require
any special measures.
With this unique solution, Eaton’s
offers a clear competitive advantage
on the European market because the
high degree of protection9) of the door
coupling handles and control panels
are preserved. With the approved
additional handle, the switch contains
two operating elements, two switch
position indicators and two locking
facilities – one each for closed and for
open doors. These handles are also
recommended for IEC/EN standard
panels, to which the described issues
also apply.
When using switches with door
coupling rotary handles and several
control panel doors, an electrical door
interlock is required. This interlock can
be defeated by specialists and must
automatically become active again
when the last door is closed. For the
electrical door interlock, our
customers prefer position switches
with mechanical locks. This solution
more closely resembles a mechanical
door interlock and provides a high
level of safety. On control panels with
only one door, this door can be directly
mechanically interlocked with the
switch through the door coupling
rotary handle. The mechanical door
interlock can also contain a defeat
mechanism10).
As alternative to door coupling rotary
handles, Eaton offers side-wall and
rear-mounted switch mechanisms,
which provide a permanent mechan-
ical connection between handles and
switches. Because of the versatile
installation options of these mecha-
nisms, an electrical door interlock
must be provided for each switch11).
Door coupling rotary handles
for North America
With door coupling rotary handles
NZM..-XTVDV.. for NZM and
NS…-NA, used mainly outside North
America, themechanically interlocked
control panel door can be opened
when handle and switch are in their
OFF position. With the NA version of
these handles – NZM..-XTVDV..-NA ,
the interlocked panel door can not be
opened in the OFF position: The handle
must be rotated further, beyond the
OFF position to release the door. This is
standard North American practice.
Both door coupling rotary handle types
are approved for North America.
Cam switches T, switch-
disconnectors P1 and P3
In North America, these switches
are industrial control equipment
according to UL 508 and CSA-C 22.2
No. 14-05). Switch-disconnectors P1
and P3 are a 3-pole design and have
two switch positions. They are used
mainly in controllers and as single
devices in motor circuits. They are
rated in HP and – if they are equipped
with auxiliary contacts – they contain
duty type information (pilot duties). The
switches have no short-circuit
switching capacity and must therefore
be fuse-protected. They can be used
for switching motor circuits and other
main circuits, and their auxiliary
contacts for switching control circuits.
Cam switches T can be manufactured
with up to eleven contact units12)and
with more than two switch positions.
They are therefore used mainly as
control switches, for example as
operating mode or measuring device
selector switches. They are rated in
HP and can also be used in motor
circuits.
According to UL 508 the devices
described above can be used as
locally installed switch-disconnectors
if the control panel contains a branch
circuit protective device (BCPD) and
the switch is, in addition, regarded as
motor disconnect according to UL 508
and CSA-C22.2 No. 14-05 and marked
accordingly on its rating plate. Eaton’s
T- and P-type switches fulfil these
requirements. For the required line
fuse ratings, see the catalog or the
rating plates of the switches.
Fuse bases and fuses
For the following reasons, the use of
circuit breakers, selected according to
the above criteria, is preferable to the
use of fuses:
• In North America only North
American fuse types must be used;
IEC/EN standard fuses are not
acceptable.
• Fuse bases for North American
fuses are very large and take up a
lot of space.
• NZM circuit breakers provide
current isolation, short-circuit
protection, overload protection
and fault signaling in a single
device and are much less
expensive and smaller than a
combination of fuse base, fuses
and overload relay.
If the use of fuses is unavoidable, we
recommend that you observe the
following points:
• North American fuses are
classified according to physical
size, breaking capacity and
current–time characteristics.
The above table provides a rough
overview.
• Motor circuits:
When using time delay fuses13):
Rated current of the max. line
fuse= 1.75 × motor rated current or
next higher fuse current rating
(max. 2.25 × motor rated current).
When using non-time delay
fuses14):
Rated current of max. line fuse =
3 × motor rated current or next
higher fuse current rating
(max. 4 × motor rated current).
• “Circuits with non-motor loads:
For these consumers line fuses are
to be selected according to the
consumer manufacturer’s
instructions. This also applies for
frequency inverters, even if motors
are connected to the frequency
inverters. In these cases the
frequency inverters are regarded
as consumers.
• “ Switchgear:
For switchgear requiring line fuses
for inherent short-circuit protec-
tion, the fuse ratings are to be
obtained from the technical data in
the catalog or from the devices’s
rating plates. For short-circuit
protection of the combination of
Eaton contactor and overcurrent
relay, see page 8/35 for the max.
line fuse ratings.
To ensure both trouble-free motor
starting and short-circuit protection of
all devices within a circuit, select the
smallest fuse required according to
criteria 2b), 2c) and 2d). Regarding the
short-circuit current rating (SCCR)
non-time delay fuses can have advan-
tages over circuit breakers.
Supplementary protectors FAZ
In North America, these devices are
industrial control equipment and
protectors (supplementary protectors
according to UL 1077 and CSA-
C22.2 No. 235)15). They are used mainly
in controllers. They can also be used
as additional protective device in
electrical devices whose incomer is
already short-circuit protected. Eaton
also provides an approved DC
switching capacity in addition to the
switch’s AC switching capacity. They
can therefore also be used in DC
circuits.
Supplementary protectors FAZ are
Recognized Components according to
UL standards. This type of protective
element is often used incorrectly. FAZ
must be used only as additional
protective device and never for branch
circuit protection (BCPD). They have
non-adjustable magnetic short-circuit
releases for short-circuit protection
and fixed-current overload relays for
overload protection. Eaton supplies
supplementary protectors with a
range of IEC/EN-compliant tripping
characteristics. The characteristic is
selected according to the protected
load type.
Supplementary protectors FAZ are
specially suitable for fuseless
protection of control circuits on the
output side of control transformers.
These protectors can also be used for
input-side protection of control
transformers, but not on the input side
of power transformers.
Circuit-breakers FAZ…-NA,
FAZ…-RT (Miniature Moulded
Case Circuit Breakers, MCCB)
Circuit-breakers FAZ…-NA and
FAZ…-RT are a further development of
supplementary protectors FAZ. They
feature large clearances and
creepage distances in the connection
area. and, as miniature molded-case
circuit breakers (MCCB), comply with
standards UL 489 and CSA-C22.2
No. 5-09. They are Listed Components
according to the UL standards and
Notes
1) In North America, electrical switching and protective devices are not
generally designed with protection against accidental contact
2) The Stop categories to IEC/EN and NFPA 79 must be observed
3) Defeat mechanisms are usually operated with a tool (screwdriver)
4) Also referred to as “side-mounted handle”
5) e.g. NZM-XSHGVR12-NA, plus further components
6) Industrial Control Panels to UL 508A and NFPA 79
7) e.g. NZM…-XHB-…-NA
8) Deliberate action
9) Or protection type – an important aspect with regard to the approval of
switchgear systems/panels
10) Operated by turning a screw on the handle with a screwdriver
11) Also on panels with only one door
12) Eleven contact units correspond with 22 contacts
13) Also called “dual element time delay fuses”
14) “Non-time-delay fuses”
15) Protective devices for additional protection (in addition to a BCPD), e.g.
splitting of circuits after a BCPD