Long story short… There are two types of frequency converters:
– Converters for pumps and fans
– Converters for conveyors, cranes or mills
The first type is more common, the second type is what we like, because it has a lot of nice features, as it is designed for demanding applications.
However, the important part is that the frequency converter has a “torque limitation”. This allows to limit the torque, which is propotional to the tension in the line.
It is very beneficial if the converter also allows closed-loop operation, because the torque accuracy becomes better in the very low end (0-20 kg). This is important for hanggliders that starts from a start trolley, as it begins to roll if the tension is more than 10-15 kg.
The “ATV61” from Schneider is build for pumps but still provides torque limitation. But the newer generation from Schneider “ATV600” build for pumps does not.
“Power limitation”, or the very common “current limitation” does not work.
ATV61 and ATV600 does not allow closed-loop operation.
The ATV71 and the newer generation ATV900 does both provide torque limitation and closed loop operation.
ATV320 does provide torque limitation but not closed-loop operation.
You just have to google the manual of the drive, and see if it provides torque limitation.
There are many brands producing frequency converters. Use the big brands as the algorithms in these provides the best performance, i.g. Schneider-Electric, Siemens, ABB, Danfoss, etc.
The frequency converters VLT FC301 and FC302 from Danfoss does also provide torque limitation and closed-loop operation.
The size of the converter should fit the motor and be able to provides sufficient current to generate the desired torque. See the table in “Design of motor”.