Danfoss VLT 6000 Application guide

Switching between mains supply and VLT

®

Switching between mains supply and VLT® frequency converter by means of a change-over switch

In certain plants, e.g. pump or ventilation plants, the use of the same motor in two different ways may be
expedient:

A) Connected direct to the mains supply so that the motor is running at a fixed speed.

B) Connected to a frequency converter so that the speed of the motor is variable.

Fig. 1 illustrates how the motor "M1" can be connected either direct to the mains or to a VLT

®

6000

frequency converter:

Switching between mains supply and VLT

®

1MN.60.R1.02 - VLT is a registered Danfoss trademark

Switching between mains supply and VLT

®

Switching between mains supply and VLT

Advantages by switching between mains supply and VLT frequency converter by means of change-over
switch

■ The possibility of switching between mains operation and operation via VLT frequency converter can be
used to increase the reliability of the plant through a redundant system

■ Operating on the mains supply, the motor can yield a very high breakaway torque

The diagram below shows how the switchgear can be made:

®

2

MN.60.R1.02 - VLT is a registered Danfoss trademark