Engineering; Overload Monitoring Of Ex E Motors; Setting Of The Overcurrent Protection Device - Eaton PKE12 Handbuch

2 Engineering

2.1 Overload monitoring of Ex e motors

2 Engineering
2.1 Overload monitoring of Ex e motors

2.2 Setting of the overcurrent protection device

36
The Ex e protection of motors is achieved by means of special design
measures. The motors are assigned to temperature classes on the basis of
the highest permissible surface temperatures. In addition, temperature rise
time t and the ratio of the starting current to the rated operational current
E
I /I are also determined and specified on the motor.
A N
The temperature rise time t
winding rises from the final temperature in normal operation to the limit
temperature when a starting current is present I
However, e motors are not safe on their own. 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

Falling below minimum current flow time at AC-4- cycle opera-
tion can lead to impermissible temperature rise of the load
(of the motor). Following minimum current flow times and
current interrupting time have to be observed unconditionally:
Minimum current flow time at AC-4-cycle operation:
• 500 ms at Class 5
• 700 ms at Class 10
• 900 ms at Class 15
• 1000 ms at Class 20
• Minimum current interrupting time at AC-4- cycle operation:
< 500 ms
With an external power supply of the PKE trip module
(e.g. connected SWD communication module) the compliance
of minimum current flow and minimum current interrupting time
is not required.
DANGER

The current-dependent protective device must be selected so
that not only the motor current is monitored but also the
blocked motor is switched off within the temperature rise time
t . This means that the protective device must be rated in such
E
a way as to ensure that tripping time t
electric motor's ratio I
ature rise time t
This is to ensure that the motor will be reliably switched off
within the temperature rise time.
The tolerance of the overcurrent release of ±20 % is to be
observed (a following example).
PKE12, PKE32, PKE65 11/17 MN03402004Z-DE/EN www.eaton.com
is the time in which the temperature of a
E
/I is not longer than the motor's temper-
A N
according to the motor's characteristic curve.
E
.
A
for the explosion-proof
A