Transcript AVOP-ELEKTRO-SKA-008

Tutorial: Mechanic - electrician
Topic:
Basics of electrical engineering
the 2nd. year
Basic characteristics of electric appliances
Prepared by: Škarka Miloš
Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002
je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.
Appliance classes are determined by the way of
providing protection against dangerous contact
in case of a malfunction of a device. Possible
ways of connection are determined according
to usage of an appliance (immovable or
movable). Only such conductors can be
connected to an appliance (L, N, PE)
corresponding to clamps on an appliance. If
there is an additional appliance adjustment
carried out, it has to be visibly marked on
connection spots (for example the discarding
of the PE clamp, while using the protection by
the nonconductive environment). Movable
appliances are meant for moving (carrying). If
such an appliance isn‘t meant to be hold in
hand, it mustn't be moved (carried) while
switched on.


Appliances have a working insulation and are
equipped with a protection clamp or a protective
contact. These are: washing machine, oven, iron,
computer, ...
Protection class II. Appliances have double or
reinforced insulation and don‘t have (mustn‘t have) a
protection clamp. Their whole surface is made of
insulating material or they can have some parts made
of metal, but always insulated with the reinforced
insulation. These are: Shaver, hairdryer, power drill,
grinder...

Protection class III. Appliances are connected to low
voltage, so to SELV and PELV networks: These are:
Low-volt bulbs, low-volt electric gardening,
healthcare or agriculture appliances...
Class of a
device
device marking or
manuals
Conditions for device connection
to an installation
Protection
class 0
Use only in the nonconductive environment
or protected by the
electric separation
electric separation carried out
individually for each device
Protection
class 1
Protective clamp
marking
or by letters PE or by the
color combination
green-yellow
Connection of this clamp to the
protective installation connection
Protection
class 2
Marking by sign
not relying on any protective
installation measures
Protection
class 3
Marking by sign
connection only to SELV or PELV
networks
The protection against the dangerous contact via reset. The
conductor PE(PEN) is connected to the conductive casing of the
device. Animate parts are separated from the casing by the
working insulation. We control the transitional resistance and
the insulation state at this device.
Three-phase
Three-phase
One-phase
Immovable appliance
connected in the TN-S
network.
Immovable appliance
connected in the TN-C
network.
Movable appliance for
connecting into the
socket.
Protection against dangerous contact via double
insulation. Surface of an appliance should be
made of an insulant. Potential metal parts have
to be separated from animate parts in a way
equal to the double insulation (plastic gears,
pulling bars etc.). This insulation barrier mustn't
be violated in any regular device malfunction (for
example during short circuit in the motor
winding there can be no casing melting). These
devices have this mark on the surface:
The immovable appliance connected in the TN-S
network. This appliance mustn‘t be connected to
the PE conductor.
The immovable appliance connected in the TN-C
network. If the appliance have the N clamp, it is
connected to the PE conductor via conductor
with a blue insulation color.
Movable appliance connected to the plug. Line has
to be permanently attached to the device. There
mustn‘t be a clamp for connecting the PE
conductor at the plug. Allowed combination of
colors of the line is blue – black (brown) and black
– brown. The line can‘t have the green-yellow color
vein.
 Basic protection: voltage reducing;
 Protection in case of a malfunction: the separation from other circuits;
 Protection construction elements: powered by the source of low voltage
by the SELV or PELV source separating the appliance from the network;
 Type of protection sign: picture no. 3 on the label
 Powering winding: two-vein;
 Connecting plug: two-pole, designed impossible to connect into the 230
V/50 Hz network.
 The appliance of the third class is recognizable by the atypical connecting
plug of the network circuit. Even here it is needed to verify this
assumption by checking the type sign.
 The voltage source can be a battery, a safety transformer, but not an
autotransformer (there is no galvanic separation)



Appliance division into classes according to
the protection
What is in the picture no. 1
What is in the picture no. 2
picture 1
picture 2



How many veins does the line for connection
of the class I appliance have?
How many veins does the line for connection
of the class II appliance have?
Why an autotransformer can‘t be used as a
source to SELV?




www. wikipedie.cz
http://www.drdys.estranky.cz
www.edunet.souepl.cz
diskuse.elektrika.cz