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Features

VVC Control system
There are basically two main control principles used by variable speed drives to control the motor speed. Within the two main areas there are several varieties of these basic principles.

In order to control the motor, it is necessary to convert the a/c. mains power to d.c. This is done internally in the drive (see also Harmonics in section called Technical Notes). After the power signal has been converted to d.c., the d.c. is chopped into square signals and directed to the three power output terminals. This is done in the internal inverter circuit.

The way the d.c. signal is chopped and shaped in the inverter is a question of how sophisticated the drive's manufacturer has decided to re-create the a.c. current for the motor. The more sinusoidal the current signal out of the inverter is, the better motor performance is obtained.

The VLT 6000 HVAC drive is using a modified PWM (Pulse-Width-Modulation) called VVCplus (Voltage Vector Control) to control the motor current and voltage, and thereby control the motor performance.

Please also refer to the book "Facts worth knowing about frequency converters", ISBN 87-87411-22-9.

 

For further information please contact your local Danfoss Company