Engineering; Overload Monitoring Of Ex E Motors; Setup Of The Overcurrent Protection System - Eaton PKZM0-0,16 Manual

2 Engineering

2.1 Overload monitoring of Ex e motors

2.2 Setup of the overcurrent protection system

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. The temperature rise time t
and the ratio between startup current and rated operational current I
calculated in addition and specified on the rating plate of the motor.
The temperature rise time t
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 temperature rise time t
This means, that the protective device must be rated in such a
way so as to ensure that the tripping time t
the 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).
Example
I /I = 6, t = 10 s
A N E
2h
20
10
5
2
1
40
3-phase
20
10
5
2-phase
2
1
200
50
20
5
2
1.5 2 3 4 6
Figure 5: Tripping characteristic for motor-protective circuit-breaker
The motor is reliably protected.
PKZM0-.../XTPR...BC1NL, PKZM0-...-T/XTPT...BC1NL 01/22 MN03402003Z-DE/EN www.eaton.com
2.1 Overload monitoring of Ex e motors
represents the time that expires for the
E
PKZM0-...
XTPR...BC1
8 10 15 20 30
Rated current
2 Engineering
E
/I are
A N
.
A
.
E
for the ratio I /I of
A A N
E
31