Parker Hannifin S.p.A S.B.C. Division SLVDN User’s Manual
Page 61 of 181
9.10. Speed control adjustment
SOME IMPORTANT CONCEPTS
SPEED LOOP: The main task of a converter is to control motor speed so that it follows as
faithfully as possible the speed request that is generally known as the REFERENCE.
Faithfully following the reference means that the motor speed should equal the reference in
static conditions and also that the motor speed is as equal as possible to the speed requested
during dynamic conditions. To carry out this task, the converter must know some of the
features of the motor used and the mechanical part attached to it. This information is
communicated to the converter by using the so-called ADJUSTMENT PARAMETERS.
ERROR: The error is the difference between the reference speed and the motor speed. The
size of the error is used by the speed loop in order to evaluate how much current must be
supplied to the motor, based on the adjustment parameters.
TORQUE: The current that circulates in the windings of the motor is transformed in
torque, thereby allowing the motor to accelerate or decelerate.
GAIN: Given the typical applications of the SLVD-N converter, when we speak of gain in
this document we refer to the rigidity of the axis, better known as the STIFFNESS.
To better illustrate what stiffness means, we can imagine a motor controlled by a converter
with a requested speed of 0. The motor shaft will appear immobile, but if we apply a torque to
the shaft, it will demonstrate an angle that is proportional to the torque applied. Suppose we
apply the rated torque of the motor and measure the stiffness in degrees. The measured
degrees will be the index of the regulator tuning quality. Clearly, it is not the only quality
index.
WHAT IS NEEDED
To adjust a SLVD-N converter correctly, an oscilloscope with memory must be used. A
technician who can use it to carry out the operation will also be needed. If it is not possible to
use an oscilloscope, a more approximate but applicable adjustment method will be illustrated
at the end of this section.
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