Section 5: Configuration of the frequency converter
5.3. Shaping the drive dynamics
Parameters related to dynamics determine the speed at which the motor
speed changes: acceleration and deceleration (braking).
parameter 1.30
– Acceleration - preset acceleration time from 0Hz to
50Hz,
parameter 1.31
– Deceleration - preset deceleration time from 50Hz to
0Hz.
Caution:
1.
Setting too short acceleration time can cause an E6 "Electric motor
current too high" fault at start-up, especially when the motor is under
heavy load.
2.
Setting too short deceleration time can cause can cause an E3 "High
DC circuit voltage" fault during ramp deceleration.
5.4. Operation in U/f scalar modes
After entering the correct nominal data of the electric motor, described in
section 4.2, the frequency converter is ready for operation in one of two
scalar operating modes: U / f linear or U / f square-law. The operating mode is
selected using parameter 1.20:
Value of
par. 1.20
Function
0
U/f linear mode-
(factory setting): It is applicable where there is a
constant load torque which does not depend on speed.
1
U/f square-law mode-
: It is applicable if the load torque grows
under the square-law speed (e.g. the electric drive of the fan).
The usage of U/f square-law characteristic causes reduction of
noise and motor losses.
It is possible to shape the U / f characteristic by specifying two points: initial
U0 (par. 1.50), f0 (par. 1.51) and intermediate U1 (par. 1.52), f1 (par. 1.53).
Fig. 5.3a shows the characteristics for linear and square-law U/f mode, and
Fig. 5.3b shows how to shape the U/f characteristic using intermediate points
U0, f0 and U1, f1.
TWERD Power Electronics
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