8400 BaseLine D | Software Manual
Motor control (MCTRL)
Selection of the operating mode
74 L Firmware 03.00 - DMS EN 5.0 - 07/2009
5.1.1 V/f characteristic control
The control structure is shown, in simplified form, in the following illustration. For the
complete representation, see
Signal flow
( 105).
Stop!
• The following must be observed when operating drives with square-law V/f
characteristic:
– Please always check whether the corresponding drive is suitable for
operation with a quadratic V/f characteristic!
– If your pump or fan drive is not suitable for operation with a quadratic V/f
characteristic, either use the V/f characteristic control with linear V/f
characteristic or the vector control mode.
• For adjustment, observe the thermal performance of the connected
asynchronous motor at low output frequencies.
– Usually, standard asynchronous motors with insulation class B can be
operated for a short time with their rated current in the frequency range 0
Hz ≤ f ≤ 25 Hz.
– Contact the motor manufacturer to get the exact setting values for the
max. permissible motor current of self-ventilated motors in the lower
speed range.
– If you select the quadratic V/f characteristic, we recommend to set a lower
V
min
.
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