The ELEKTRO
1/2014
Customer information for electricians
30th Volume, 125th Edition
Here,
the clamping units
are scorched!
The whole distribution
board could have been
burnt!
Collection of new ideas in the Electrotechnical Industry
Dear reader,
Proximity to electricity is an integral
part of our daily lives and has the
potential to profoundly affect us in
many ways.
Electrical faults have been identified
as one of the common causes for
fires in buildings. Most of these
faults have been traced to loose
terminations which go undetected
till the damage is done.
With
more
than
80
years
of
experience, we are in a good
situation to caution our readers
against common pitfalls and tips
to ensure that you have a safe and
reliable installation.
Please do not hesitate to reach out
to your local HENSEL specialist if
you need more information.
Regards,
Felix G. Hensel
Managing Director of
Gustav Hensel GmbH & Co. KG
Still a “hot” topic:
If terminals get too hot
Safe connection of conductors
The safety of every electrical installation,
including the devices installed in it,
depends on terminals used millions
of times for connecting cables and
conductors.
For example, a bad connection within
the PE-link can lead to absence of the
required residual current for switching off
the protective device and thus personal
safety is no longer guaranteed.
Concerning many connections the
electrician makes every day, it is often
difficult to consciously be aware of the
functional inter-connection between
terminals, the conductors to be
connected and one’s own actions.
This edition of Elektro Tipp shows how
screw-type terminals can be safely
connected to.
A bad terminal connection can cause damage...
An bad terminal connection can cause damage!
Different terminal
technologies
Terminals with screw connections
Terminal 10 mm2
wired, re-wire and take
a photograph
Conductors are mechanically and
electrically connected together using a
clamping screw. Selecting the correct
terminal and torque determines the level
of safety of the terminal connection.
Terminals with screw-less connections
Plug-in terminals automatically ensure
that the contact is made by the
regulating force of the spring on the
conductor and will therefore not be
considered any further here.
In the following, Elektro-Tipp is only
concerned with “screw-type terminals”.
How does a terminal connection become bad and what are the possible consequences?
Clamping units become bad when the conductor is no longer ensuring safe current transfer.
Examples of bad terminal connections:
An unsuitable terminal for the
conductor
Terminals are established for certain
specific types of conductor and crosssections. Connection of different types
of conductors and cross-sections at
the same clamping unit is usually not
permissible.
Mechanical tensions in the terminal
These occur, for example, due to a lack
of strain relief or not sufficient wiring
spaces, particularly for conductors with
a large cross-sectional area.
The probable consequences:
The contact begins to char and becomes a potential fire risk.
A faulty terminal usually represents a high fire risk. If there is an imperfect PE conductor
connection (PE) then personal safety is no longer ensured in the case of a fault!
What are the characteristics of a safe terminal connection?
Wrong torque
If there is an excessively high torque,
the terminal lacks the properties of the
spring needed to produce an optimal
contact pressure.
What are the characteristics of a safe terminal connection?
Three factors determine the safety of a connection:
1. Selecting a suitable terminal
2. Adequate wiring space and strain relief for the cable
An adequately
large wiring
space allows
the conductor
to be connected
pressure-relieved.
The terminal connection must relieve all strain and pressure
on the conductor, for example, by means of a cable gland
or cable strain relief device. The conductor must be inserted
into the terminal in such a way that no external mechanical
effects can act upon the terminal connection. This applies for
all conductors, particularly for solid conductors with a large
cross-section.
3. Permanent contact pressure through an optimal torque and spring effect
Ensuring the correct contact force is a basic requirement
for terminals: It is generated through simple operation of the
clamping screw. The contact is safe if a good connection and
safe current transfer to a defined location is guaranteed with
the prescribed power (optimal torque).
The amount of torque required depends on the terminal
construction and size.
Only the correct
torque guarantees
reliable terminal
connections!
The spring tension of the contact is set by using the
prescribed torque. In this way, the required contact pressure
is generated and the specified spring deflection is achieved.
An excessively high torque destroys the spring effect.
If the torque is too low the contact pressure is not sufficient
enough, and this can result in a loose connection or the
contacts becoming charred.
Tightening torque in
the screw-type terminal
Drehmoment
in der Klemmschraube
Traction force in
clamping
Zugkraftunit
im Bügel
Busbar
The spring
effect
„Zugbügel“
Stromschiene
Current
Strom
xes
transfer
Leiter
Conductor
xes
n Bo
nctio
ble Ju
ls
DK Ca al Detai
nic
Tech
inals
Term
mitted.
not per
unit is
Rated
clamping
t
cross of
at one
Curren
ections
ning carrying
section l
Tighte
t cross-s
ina
y
term
c(Cu)
differen
que
capacit
tors
Condu be tor
and/or
conduc ductors
s to
per
ed
tor
con
Rat
for cop t types of
ting connected
ing
inals
ren
2
connec ty
Clamp
pole
g term
of diffe
aci
n
per
6 mm
ctin
tion
ts
cap
ctio
uni
2 and
Conne connec ferrule
e
le jun
The
–
mm of
in cab
per pol
Hint: ible with end
es
Fixed
Nm
typ
1 = flex
1.2
tors
f
inal
boxes
conduc
of term
1-2
Type
1-3
6 sol
1-4
4 sol
1
sol
1-6
5,
2.5
5, D 922 5
1.5 sol
5, D 912 DP 902
D 902 D 9045,
5,
2
D 924 1, DP 922
6
2
DP 922 5, DE 932
6
10 mm
DE 932 5, DE 934
5
–
DE 934 5, KD 504
5
04
KD 502 5, KF 504
1.5 Nm
DKL
5,
KF 502 5, KF 904
5,
2
1-2
202
5
KF 902 5, KF WP
16 mm
1-3
WP 302
10 sol
DN 203 2045, KF
1-4
63 A
sol
6
WP
1
KF
3045
1-4
4 sol
2 Nm
KF WP
2.5 sol
5,
1-2
K 906 5
2
5
1-4
16 s
KD 506 5, KF 906
35 mm
sol
1-4
506
10
2
KF
3065
1-4
102 A
6 sol
KF WP
5
2-6
3 Nm
4 sol
5, K 810
f1
06
K 910 5
KKL
2.5 sol,
1-2
5
KD 510 5, KF 910
2
f1
1-4
35 s, 1
KF 510 2105,
50 mm
f
1-4
25 s, 1
2
A
KF WP 3105
f
150
2
s,
1-6
WP
16
10
KF
f1
5, K 950
KLS
1-6
12 Nm
10 sol,
5, K 825
K 925 5
6 sol
1-4
5
KD 525 5, KF 925
2
1-4
50 s
KF 525
50 mm
s
1-4
35
2
150 A
1-6
25 s
12 Nm
25
16 s
4
KLS
K 950
1-4
2
1-4
50 s
70 mm
1-4
35 s
2
216 A
5,
s
1-6
25
5, K 950
10 Nm
16 s
5, K 935 5,
K 705 5, KF 950
1-4
50
5,
KLS
2
KF 935 5, KF 550 5
1-4
70 s
70 mm
KF 535 5, KD 435
s
1-4
50
4
KD 535
216 A
1-4
35 s
1-4
10 Nm
25 s
4
K 700
16 s
1-4
S 51
permitted.
g unit is not Hensel provides information
about the torque
Rated in Nm for
nt
rreall
u
C
g
in
n
screw-type
crossterminals
Tighte
carrying
e
ction of
u
secatalogue.
in its main
torq
capacity
terminal
ne clampin
ections at o
rent cross-s
g
Aluminium conductors place special demands on a terminal
and on pre-treatment of the conductors.
Selecting the correct terminal according to the type of
conductor and cross-section. Solid, stranded or flexible
conductors have a different contact behaviour. The
connectable nominal cross-section can be taken from the
marking on the terminals.
ConducRated
tors to be
connecting
connected
capacity
per pole
2
mm and
types of
2
Summary:
A terminal connection is safe if all three
factors mentioned are observed
Terminal connections, as well as
the whole electrical plant, must be
checked regularly.
KV Small-type distribution
boards up to 63 A,
3 to 54 modules, IP 54- 65
Check regularly
Inspection intervals
Terminal connections must be checked
Electrical installations must be checked at
regularly, as well as the entire electrical
regular intervals so that any defects can
system.
be identified and eliminated. Depending
In this way the electrician is also ensuring
on the devices and terminals used, the
the safety and reliable operation of the
inspection intervals may be different.
electrical installations over the long-term.
Thus, terminals of aluminum conductors
Distribution boards
Combinable enclosure system
with door up to 250 A, IP 66
Phone: +91-44-3727 0202
Fax: +91-44-3727 0200
Email: info@hensel-electric.in ∙ www.hensel.in
DK Cable junction boxes
2
1.5 to 240 mm , IP 54-67
checks than terminal connections of
Mi Distribution boards
up to 630 A, IP 54-65
copper conductors. (See also ElektroTipp 2/2013 Professional Connection of
Aluminium Conductors) .
The ELEKTRO
More information about
Customer Informat
ion for Electro-technica
l Specialists
service intervals can be
We can also
connect aluminum
conductors
in this terminal?
2/2013
Why?
Do we have to note
something special?
Cable entry systems
Dear Reader,
ideas in the Electrotechnic
al Industry
found in the Installation
Collection of new
and Maintenance
The higher the price
for copper rises,
the more people
in the electrical component business
look for a possible
substitute for this
increasingly expensive raw material.
When it comes to
cables, people are
turning to aluminum
conductors with
larger cross-section
s.
In this edition of
Elektro Tipp we
will
deal with the professional
connection
of aluminum cables.
It requires special
installation expertise
and of course the
right cable junction
boxes with terminals for aluminum
and copper conductors.
Hensel has offered
a complete range
of products for this
very purpose for
years and they have
proven very reliable and can also
help produce reliable connections with
aluminum cables
when the instructions
are followed.
We believe that
we have once again
proven our skill
in the connection
of
cables and conductors
and have
helped electricians
to solve often urgent problems with
our range of products and services.
We look forward
to working with you
in the future.
Manual of the equipment manufacturers.
Felix G. Hensel
Managing partner
of
Gustav Hensel GmbH
&
Professional Connection
of Aluminum Conduc
tors
Special expertise
:
is needed!
To save money,
more and more
Most devices and
people are thinking
terminals are
about using designed
aluminum cables
only for connectin
instead of copg
copper cables.
per. It is especially
Therefore special
true of wires requireme
with larger cross
nts need to be adhered
sections.
to with aluminum
conductors.
Co. KG
Construction board panels
up to 630 A, IP 44-65
How can aluminum
cables be
properly connect
ed?
Sunguvachathram - Walajabad Road
4th km behind Samsung/Flextronics
Sriperumbudur - 631 604 ∙ Kanchipuram Dist, Tamil Nadu
need special expertise and different
PASSION FOR POWER.
Three Factors Determine a Safe Terminal Connection
1. The suitable terminal
n the material of the conductor and its insulation
n the number and shape of the wires forming the conductor (identical for each clamping unit)
More detailed information on this theme
Proceed to download at www.hensel.in!
Practical working aid
for electricians in poster formate.
Type
Shape
solid (sol)
round conductor / solid
sector shaped conductor /solid
stranded (s)
round conductor /
stranded
sector shaped conductor / stranded
rigid [r]
flexible (f)
Hint: Terminals without marking „r“ (rigid conductors only), „f“ (flexible conductors only), „s“ or „sol“ (solid conductors only) can be used to connect all types of conductors.
Pole with one clamping unit
Pole with two clamping units - only the same cross
section and cable type per clamping unit
Labelling with max. number and diameter of conductors to be connected
per pole
2. Adequate wiring
space
Too small wiring area
n Bending radius of the
conductors is too small
Adequate large wiring area
n no mechanical stress of the
terminals
n additional strain relief
n Conductors standing
inclined to the
terminal
3. The optimum torque
Effects with terminals with steel body

Only the correct torque guarantees
reliable terminal connections!
Nm
Tightening torque in
the screw-type terminal
Terminals for incoming cables
F
Traction force in
clamping unit
Elasticity
Terminals for
incoming cables
Busbar
2-5-pole, for copper and aluminium conductors, zum Einbau in Mi-Leergehäuse Größen 2 bis 8,
fixed on mounting plate 300 x 300 mm, with Befestigungsschrauben.
Mi VE 120
4-pole
Mi VE 125
5-pole
Mi VE 240
4-pole
Mi VE 245
5-pole
Rated connecting capacity
150 mm2
150 mm2
240 mm2
240 mm2
Current carrying capacity
Mi VE 302
2-polig
Mi VE 303
3-polig
Mi VE 304
4-polig
300 mm2
300 mm2
mm2 mm2
300 mm2
630 A
630 A
630 A
Tightening torque
20 Nm
20 Nm
40 Nm
40 Nm
50 Nm
50 Nm
Clamping units per pole
250 A
2
250 A
4
400 A
2
400 A
4
2
50 Nm
4
Current
transfer
Conductor
Gustav Hensel GmbH & Co. KG · D-57368 Lennestadt · www.hensel-electric.de
Examples to tightening torques:
labelling of terminal, specifications in the Hensel main catalogue
HEI, INDIA
Delivery in India via Hensel authorized
distributor network ­spanning 130 cities and industrial centers.
Delivery in South East Asia via Hensel authorized distributor
network in all ASEAN countries.
Delivery in Middle East via Hensel authorized distributor n
­ etwork
in all GCC countries.
R. Rajesh
Managing Director
Hensel Electric India
Pvt Ltd
info@hensel-electric.in
www.hensel.in
Hensel Electric India Pvt Ltd
Industrial Electric Power Distribution Systems
35 Kunnam Village
Delivery only via electrical
wholesalers!
Photovoltaik distributors
that meet the standards
n the cross-section of the conductor (identical for each
connection)
n the number of conductors to be connected with each
other (see terminal labeling)
Overview of types and shape of conductors