Protective Functions; Ramp Stop And Hardware Current Limit - KEB COMBIVERT F5 MULTI Applications Manual

Protective Functions

6.7 Protective
Functions
6.7.1 Ramp Stop and
Hardware Current
Limit
Fig. 6.7.1.a Survey ramp stop function
see „Digital outputs"
do.0...do.7 value „15"
Pn.25 Deceleration stop / DC-voltage
LA-Stop
LD-Stop
© KEB Antriebstechnik, 2002
All rights reserved
The protective functions protect the inverter against switch off caused by overcurrent,
overvoltage as well as thermal overheating. Furthermore, you can restart the drive
after an error automatically (Keep-On-Running).
The ramp stop function essentially fulfills two tasks. It prevents
• overcurrent errors (E.OC) during the acceleration phase,
• overvoltage and overcurrent errors (E.OC/E.OP) during the deceleration phase,
by stopping the ramp on exceeding adjustable levels. Moreover, the ramp stop function
can be activated by a digital input. Beyond that a hadware current limit is integrated
which intervenes independent of the software and is thus much faster.
Although these functions can be activated in controlled operation, this is to be avoided,
since the KEB COMBIVERT regulates here at the torque limits.
Ramp stop
Pn.22 Ramp stop/Activation
LD-Stop (I) LD-Stop (U) LA-Stop
0 off off
1 off off
2 off on
3 off on
4 on off
5 on off
6 on on
7 on on
200...800 V
The function protects the frequency inverter against switch off caused by overcurrent
during the acceleration phase. The current level is adjustable with Pn.24 in the range
of 0...200 %. The protective function can be deactivated with Pn.22.
During deceleration energy is refed into the frequency inverter, which causes a rise
of the DC-link voltage.
If too much energy is refed the inverter can trip to error OP or OC. If the LD-Stop
function is activated with Pn.22, the DEC-ramp is regulated according to the adjusted
DC-link voltage (Pn.25) or the DC-link current (Pn.24), so that errors are avoided to a
large extent.
An activation of LD-Stop(I) - functionality leads to the deceleration stop, if the setpoint
is reduced or if the protective function Maximum Constant Current (stall-function) should
cause a reduction of the frequency. Consequently inverters „get stuck" at high speeds
concerning applications like e.g. pumps / fans and overload errors can occur.
Since the error E.OP occurs far more often during deceleration and the avoidance of
such errors is covered by the function LD(U), LD(I) should be activated only if it is
absolutely necessary (overcurrent error during deceleration).
Name: Basis
KEB COMBIVERT F5
Functional Description
Pn.23 Input selection
off
on
off
on
off
on
off
on
Pn.24 Max. Ramp current
0...200 %
Datum
04.05.04
Ramp stop
0...4095 (Default 0)
also see
„Digital inputs)
Kapitel Abschnitt Seite
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