109
SPX advanced – description of parameters
SPX ADVANCED APPLICATION MANUAL
SVCH0203—October 2017 www.eaton.com
Set then the midpoint voltage to VÖ2 * Zero Point
Voltage and the midpoint frequency to (Zero Point
Voltage/100%)*Nominal frequency of motor)
Step 2 (If needed): Activate speed control or U/f
optimization (Torque boost).
Step 3 (If needed): Activate both speed control and U/f
optimization.
otee:
N
In high torque – low speed applications – it is likely
that the motor will overheat. If the motor has to run
long times under these conditions, special attention
must be paid to cooling of the motor. Use external
cooling for the motor if the temperature tends to rise
too high.
Code
ID
Parameter
Notes
P1.8.4.1
109
U/f Optimisation “U/f optimization”
Automatic torque boost
The voltage to the motor changes proportionally to required torque which makes the
motor produce more torque at start and when running at low frequencies. Automatic
torque boost can be used in applications where starting torque due to starting friction
is high, e.g. in conveyors. Even with linear U/f curve, the torque boost has an affect but
the best result will be achieved after the identification run when programmable U/f
curve is activated.
P1.8.4.2
108
U/f Ration selection “U/f ratio select”
Linear: 0
The voltage of the motor changes linearly from zero point voltage to the field
weakening point where the voltage at FWP is supplied to the motor.
Squared: 1
The voltage of the motor changes from zero point voltage following the squared curve
form zero frequency to the field weakening point. The motor runs under magnetised
below the field weakening point and produces less torque. Squared U/f ratio can be
used in applications where torque demand is proportional to the square of the speed,
e.g. in centrifugal fans and pumps.
Programmable U/f curve:
2 The U/f curve can be programmed with three different points.
1. Zero point voltage
2. Midpoint frequency and Midpoint voltage
3. Field weakening point and field weakening point voltage
Programmable U/f curve can be used if more torque is needed at low frequencies.
Make the Identification run for optimal setting (ID631).
Linear with flux optimisation:
3 The frequency converter starts to search for the minimum motor current in order to
save energy. This function can be used in applications with constant motor load,
such as fans, pumps etc.
P1.8.4.3
602
Field weakening point “Field weakngPnt”
The field weakening point is the output frequency at which the output voltage reaches
the field weakening point voltage.
P1.8.4.4
603
Voltage at field weakening point “Voltage at FWP”
Above the frequency at the field weakening point, the output voltage remains at the
set maximum value. Below the frequency at the field weakening point, the output
voltage depends on the setting of the U/f curve parameters.
When the parameter Motor nominal frequency is set, the parameter Field weakening
point is automatically given the corresponding value. If you need different values for
the field weakening point and the maximum output voltage, change these parameters
after setting the Nominal frequency.
In closed loop control this defines maximum voltage to the motor, can be increases if
sufficient DC voltage is available.
P1.8.4.5
604
U/f Curve, middle point frequency “U/f Mid Freq”
If the programmable U/f curve has been selected with parameter U/f ratio this
parameter defines the middle point frequency of the curve. See also parameter Middle
point voltage.
When the programmable U/f curve is selected this value is set to 10 % of motor
nominal frequency.
