Page 23
Issue 08/2013
iMAPLA system description
Function description
4.4
Function description
4.4.1
Lift load (switch on lifting magnet)
After pressing the button (Joystick S1) on the MMI manual control unit, the
generator sends a voltage out to magnetise the lifting magnet.
When switched on for the first time after a system start, the current that
flows through the lifting magnet will increase relatively slowly, exponentially,
until the rated current is reached. The rated voltage on the lifting magnet is
approx. 230 V. Magnetisation without impulse excitation (up to 280 V).
Ö
Fig. 2, Characteristic curve, “lifting”, page 24
To accelerate the magnetisation, the
i
MAPLA-System uses
quick
magnetisation with impulse excitation
for all subsequent magnetisations.
This method only works when the system knows the rated current of the
lifting magnet. The electronic system continuously measures the current in
the lifting magnet. The current measured before switch-off is saved and set
as the rated current. It will later serve as the reference value for automatic
demagnetisation when releasing the load and for the next energisation
when lifting the next load.
The next time the lifting magnet is energised, the system uses the quick
magnetisation with impulse excitation. Until the saved nominal current
value is reached, a significantly higher voltage is generated across the lifting
magnet (impulse excitation which can be up to 280 V d.c.).
