The bit B0 controls the search direction. When you set the bit to 0, the shaft frequency is
searched in 2 directions, the positive and the negative. When you set the bit to 1, the shaft
frequency is searched only in the frequency reference direction. This prevents the shaft
movements for the other direction.
The bit B1 controls the AC scanning that premagnetises the motor. In the AC scanning, the
system sweeps the frequency from the maximum towards zero frequency. The AC scanning
stops when an adaptation to the shaft frequency occurs. To disable the AC scanning, set the
bit B1 to 1. If the value of Motor Type is permanent magnet motor, the AC scanning is
disabled automatically.
With the bit B5 you can disable the DC pulses. The primary function of the DC pulses is to
premagnetise the motor and examine the rotation of the motor. If the DC pulses and the AC
scanning are enabled, the slip frequency tells which procedure is applied. If the slip
frequency is less than 2 Hz, or the motor type is PM motor, the DC pulses are disabled
automatically.
P3.1.4.9 AUTOMATIC TORQUE BOOST (ID 109)
Use this parameter with a process that has a high starting torque because of friction.
The voltage to the motor changes in relation to the necessary torque. This makes the motor
give more torque at the start and when the motor operates at low frequencies.
The torque boost has an effect with a linear U/f curve. You can get the best result when you
have done the identification run and activated the programmable U/f curve.
9.1.1 I/F START FUNCTION
When you have a PM motor, use the I/f Start function to start the motor with constant current
control. You can receive the best effect with a high power motor. With a high power motor,
the resistance is low and it is not easy to change the U/f curve.
The I/f Start function can also give a sufficient torque for the motor at startup.
Motor Current
Time [s]
I/f Start
Frequency
I/f Start Current
Output Frequency
Fig. 25: The I/f start parameters
VACON · 232 PARAMETER DESCRIPTIONS
9
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