Speed Control Adjustment - Parker TWIN-N Series User Manual

Parker Hannifin S.p.A. Divisione S.B.C.

5.9 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 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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user's manual TWIN-N and SPD-N