N
L1
M
3
L2
L3
F1 - F3
K1
10
11
AC 220 ... 240 V
Us
F4
U
V W
S1
S2
k1
K1
H1
S3
2)
A1
A2
T1
T2
Y2
Y1
24
21
22
14
12
11
2)
2)
1)
1)
1)
T1...T3
3)
Fig. 11:
Connection example with PTC thermistor tripping unit
U
S
Control voltage
T1 – T3
PTC resistor sensor
S
1
OFF button
H1
Tripping indicator
S
2
ON button
M
Motor, 3-phase
S
3
RESET button
1)
For devices with two relay outputs only
K1
Contactor
2)
For MSR type (model) only
F1 – F4 Fuses
3)
Only for order no.: P 4768 052 FQ and P 4768 052 FE
Procedure
► After shut-down, switch the tripping unit back on manually via the installed RESET button or via
the external RESET S3.
– Switching on mains detected as automatic RESET.
5.8 Observing the motor torque
When the magnetic coupling is overloaded, there is a loss of synchronization between the inner and
outer coupling. The eddy currents that are caused as a result lead to the overheating of the magnetic
coupling. When the vacuum pump is used as intended, the magnetic coupling is unlikely to become
overloaded.
Causes of overloading if not used as intended
● The backing pump cannot handle the volume of gas required by the Okta ATEX (increased pres-
sure build-up between the roots pump and the backing pump). You must observe the volume flow
ratio of ≤ 10:1 between the roots pump and the backing pump.
● Failure of the backing pump. In this case, you must switch the roots pump off immediately.
● Increased starting torque, e.g. caused by a motor not specified by Pfeiffer Vacuum.
● The piston is blocked due to deposits.
● The roots pump was switched on before the backing pump.
Torque limitation Okta 500 ATEX
A soft starter (e.g. Siemens 3RW30, Eaton DS7) or a frequency converter enables you to
limit the torque.
● Maximum permissible motor torque
28 Nm
Installation
32/60
