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.
5.9.2 Checking the direction of rotation
Fig. 12:
Check of direction of rotation
Procedure
1. When switching on for the first time, check the roots pump direction of rotation.
2. Switch the vacuum pump on briefly (2 to 3 seconds)
– The motor and coupling must rotate clockwise (see directional arrow on housing cover).
3. If the direction of rotation is incorrect, swap the 2 phases of the connection cable in the terminal
box.
5.9.3 Connecting the PTC thermistor temperature sensor (3TF)
You should connect pump motors equipped with PTC thermistor temperature sensors (3TF) in the sta-
tor winding to a PTC resistor tripping device for protection against overload. Tripping units store the
shut-down.
Other proven motor monitoring systems can also be used.
Installation
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