Special functions
© KEB, 2012-10 COMBIVERT F5-A, -E, -H Page 7.15 - 5
7
1
The braking time is dependent on the actual frequency (ru.03), not from the actual speed (ru.07). The
reference value for the calculation of the braking time, however, is a speed (dependent on ud.02 "control
type", for "4: F5-M / 4000rpm“ is the reference value 1000 rpm). To calculate the braking time, the actual
frequency (ru.03) must be converted to a speed according to the following formula:
ru.03 * 60
———————————
pole-pair number of the
motor
2
Actual braking time = Pn.30 * ru.03 * 60 / pole-pair number of the motor / reference value (The reference
value is dependent on ud.02 "control type". The reverence value in 4000 rpm mode is 1000 rpm and 2000
rpm in 8000 rpm mode etc.)
3
Actual braking time = Pn.30 * Pn.32 / reference value (The reference value is dependent on ud.02 "con-
trol type". The reverence value in 4000 rpm mode is 1000 rpm and 2000 rpm in 8000 rpm mode etc.)
4
These adjustment are operative only if in Bit 0...3 "DC-brake mode" the value "10: conditions" is chosen.
If the same condition is also set for speed search, DC-brake has priority.
7.15.1.1 V/F characteristic control
In v/f-characteristic control, a DC voltage is applied to the motor. The max. braking voltage is set with Pn.31
"DC braking max voltage".
The current is limited only by the inverter. If the inverter is oversized compared to the motor, the maximum bra-
king voltage (Pn.31) must be decreased to avoid overheating of the motor.
At large ratings the maximum braking voltage can lead to overcurrent errors (E.OC). In that case reduce it with
Pn31.
7.15.1.2 Speed-controlled operation without feedback (ASCL)
In ASCL-mode, a DC current is impressed on the motor.
The braking current is set with Pn.33 "DC-brake max. current ASCL". The current can be preset in a range of
0...400.0% with respect to the rated motor current (dr.00).
The current is limited above by the permissible standstill current (see technical data of the corresponding inver-
ter) or by dr.37 "maximum current", if in dS.03 the maximum current mode is activated. The lower limit is given
by the magnetising current.
After completion of the DC braking function, the rated ux of the machine must ow before the motor is started.
To that end, "Wait for magnetisation = 128: on" (Bit 7 = 1) must be programmed in parameter dS.04. The tor-
que display is not valid in the DC braking (display always = 0 Nm).
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