H - I - J PROGRAMMER’S MANUAL V8.94.11-
- 55 -
7. U/f ratio menu
In this menu the voltage vs. frequency curve can be given or modified.
Followings can be set here:
• typical characteristics,
• U/f modifications,
• points of any frequency vs. voltage curve
Explanation, further submenus
This value has to be set according to the torque
requirement of the driven machinery. In general
case for normal (linear) pump or ventilator a
characteristic modified to quadratic is desirable.
(In the torque vs. frequency curve the first means
a curve with constant torque and the second
means a curve with linear increasing torque.)
Here the voltage value necessary to assure the initial flux can be set, and the normal characteristic
can be corrected. (See picture with U/f characteristics)
7-2-1 U boost
The starting voltage to be given to the standing
motor.
7-2-2 Quadratic characteristic modification
Here the state between linear and quadratic
characteristic can be set according to demand. At
0% linear, at 100% quadratic.
Creating an arbitrary voltage vs. frequency characteristic by stating corresponding points.
(Between two points stated, the voltage will change in linear way.)
The points have to be stated according to increasing frequencies!
First point of the characteristic is always “f1” frequency - “U1” voltage,
the upper corner point of the characteristic is “f6” frequency - “U6” nominal voltage
below „f1” frequency - the output voltage is “U1”,
above „f6” frequency - “U6”
The setting is the same as that of item 7-3-1 first point.
• It is practical to choose a small value for f1.
• It is practical to choose f nominal for f6. (This can substitute for setting Un.)
• At lower frequencies, it is practical to state the points closer to each other
• The U starting voltage exerts its effect at each characteristic.
• In the output motor voltage the U starting voltage is summed up quadratically with the selected characteristic,
that is:
U
motor
=
U
boost
2
+U
characteristic
2
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