W2
U1
L1
V2
V1
W1
U2
L3
L2
W2
U2
V2
U1
V1
W1
L1
L2
L3
Fig. 9:
Star circuit for high voltage
The ends of the 3 phases are connected in the star point. The terminal voltage is √3 times the phase
voltage, the mains current is equal to the phase current. The star circuit is marked with the Y symbol.
5.7.2 Checking the direction of rotation
Fig. 10:
Checking the direction of rotation
Procedure
When switching on for the first time, check the roots pump's direction of rotation.
1. Switch the vacuum pump on briefly (2 to 3 seconds)
– The motor and coupling must rotate clockwise (see directional arrow on housing cover).
2. If the direction of rotation is incorrect, exchange the two phases on the connection cable in the
terminal box.
5.7.3 Connecting the PTC thermistor tripping unit
Motors equipped with PTC in the stator winding must be connected to a PTC thermistor tripping unit as
protection against overload. Tripping units store the shut-down.
Installation
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