7 Special functions
This function is only available if the controller is in the closed loop mode (bit 0 of object 3202
h
must be set to
"1").
There is an exception: If I
2
t is activated in open loop mode, the current is limited to the set rated current,
even if the set maximum current is larger. This function was implemented for safety reasons so that one can
switch from closed loop mode with very high, brief maximum current to open loop mode without damaging
the motor.
7.2.2 Object entries
The following objects affect I
2
t motor overload protection:
●
2031
h
: Peak Current – specifies the maximum current in mA.
●
203B
h
:1
h
Nominal Current – specifies the rated current in mA.
●
203B
h
:2
h
Maximum Duration Of Peak Current – specifies the maximum duration of the maximum current
in ms.
The following objects indicate the current state of I
2
t:
●
203B
h
:3
h
Threshold – specifies the limit in mAs that determines whether the maximum current or rated
current is switched to.
●
203B
h
:4
h
CalcValue – specifies the calculated value that is compared with the threshold for setting the
current.
●
203B
h
:5
h
LimitedCurrent – shows the momentary current value that was set by I
2
t.
●
203B
h
:6
h
Status:
○
Value = "0": I
2
t deactivated
○
Value = "1": I
2
t activated
7.2.3 Activation
Closed loop must be activated, (bit 0 of object 3202
h
set to "1", see also chapter Closed Loop). To
activate the mode, the three object entries mentioned above (2031
h
, 203B
h
:1,
h
203B
h
:2
h
) must have been
appropriately specified. This means that the maximum current must be greater than the rated current and a
time value for the maximum duration of the maximum current must be entered. If these conditions are not
met, the I
2
t functionality remains deactivated.
7.2.4 Function of I
2
t
From the specification of rated current, maximum current and maximum duration of the maximum current, an
I
2
t
Lim
is calculated.
The motor can run with maximum current until the calculated I
2
t
Lim
is reached. The current is then
immediately reduced to the rated current.
The relationships are illustrated again in the following diagram.
Version: 2.0.1 / FIR-v1650 88
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