Table of Contents
Advertisement
Available languages
Available languages
01/11 MN03402002Z-DE/EN
Overload monitoring of
Ex e motors
Setup of the overcurrent
protection system
j
2
Engineering
The Ex e protection of motors is achieved by means of
special design measures. The motors are assigned to temper-
ature classes on the basis of the highest permissible surface
temperatures. The temperature rise time t
between startup current and rated operational current I
are calculated in addition and specified on the rating plate of
the motor.
The temperature rise time t
for the temperature of the motor winding to rise from its final
rated operational temperature up to the limit temperature,
at a startup current of I
However, Ex e motors are not intrinsically safe. Explosion
safety can only be achieved by taking additional measures
during installation and by selecting appropriate operating
conditions (PTB testing regulations), e.g. by adding a
correctly rated and set overload protection to the circuit.
Danger!
The selected overload protection system must not only
ensure proper monitoring of the motor current, but also
that the seized motor is switched off within the tempera-
ture rise time t
.
E
This means:
The protective device must be rated in such a way so as to
ensure that the tripping time t
Ex e motor is not higher than its temperature rise time t
according to its characteristics curve, in order to safely
switch off the motor within that period (a following
example).
and the ratio
E
represents the time that expires
E
.
A
for the ratio I
A
/I
A
N
/I
of the
A
N
E
31
Advertisement
Chapters
Table of Contents
