ACS 300 User’s Manual 65
Chapter 7 - Drive Parameters
DC BRAKE
When the STOP parameter is set to DC BRAKE or DEC+HOLD,
this parameter sets the DC injection time in seconds. If the
braking time is too short, the drive stops by coasting after the DC
braking time has elapsed.
Note:
Injecting DC current into the motor causes the motor to
heat up. In applications where long DC BRAKE/ DEC+HOLD
times are required, externally ventilated motors should be used.
U/f RATIO
The voltage to frequency ratio in the frequency range 0 Hz to
nominal motor frequency can be set either LINEAR, SQUARE or
OPTIM.
LINEAR
The voltage of the motor changes linearly with frequency in the
constant flux range. Linear U/f (V/Hz) ratio is normally used in
constant torque applications, or where the torque characteristics
of the load are linear with speed.
SQUARE
Squared U/f (V/Hz) ratio is normally used in applications where
the torque characteristic of the load is proportional to the square
of the speed, such as centrifugal pump or fan systems.
OPTIM
The motor voltage is automatically controlled to minimise motor
losses and noise. This setting is suitable for a drive which has
slowly changing load torque and a motor which operates mainly
below nominal load.
Note! Parameter MOTOR I must be set correctly for best results.
Note! OPTIM cannot be used in a system where two or more
motors are connected in parallel to one ACS 300.
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