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What is the difference between Altivar 61 and Altivar 71 drive which makes the latter suitable for constant torque applications?

Constant Torque: ATV71
The constant Torque is one of the most common profile found in industrial applications.

The resistant torque is almost not depending on the speed.
Constant torque are typical for hoisting applications, lift, conveyors, cranes ..

These load demands very good performances in torque on the whole speed range.
And because the resistant torque represents almost 100% of the nominal, the drive must be able to provide a high transient torque at starting to accelerate, usually up to 200% of the nominal torque.
The corresponding variable speed drive offer is called “Constant torque” or “High torque”


VARIABLE TORQUE: ATV61
It’s the typical torque profile of centrifuge pumps or compressors and fans.

At starting the resistant torque is weak 10 to 20% of the nominal.
It increases quickly after with the square of the speed

The main constraints appears around the nominal speed, a low speed variation leads to a strong torque variation.
 
It requires a soft-starters or a speed drives with less transient performances than for constant torque applications.
A specific offer called “variable torque”  or “standard torque” answers to pump and fan applications.
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