28/06/2013 7CH4Q107_E_4
20
OVERLOAD PROTECTION
In the programming mode set the rated current and overload time for the motor:
The protection will be activated each time the current overcome the value In +10% and the
overload time is as shorter as higher is the overload according to the function. After the
integration time the controller will stop the machine and an alarm (A11) will be activated.
First of all, the ammeter constant ( K ) has to be calculated using the heat-sink
temperature, the maximum current and the rated current as follow:
( Imax
2
- In
2
)*t
K =
In =
Imax =
t =
rated motor current,
max motor current,
overload time at the max
current,
Once calculated the “K”, is possible to calculate the ammeter time protection at your
working current:
ccccccc
K
ccccccc
twrk=
( Iwrk
2
- In
2
)
In =
Iwrk =
K =
rated motor current,
max motor current,
ammeter constant.
Example:
•
Current limit = Imax = 90 Amps,
•
Rated current = 30 Amps,
•
Overload time = t = 30 seconds,
•
Working current = Iwrk = 50 Amps,
Step1: K calculation:
K = ( Imax
2
- In
2
)*t = (90
2
-45
2
)*30 = 182250
Step2: protection (ammeter) time:
K
182250
t =
( Iwrk
2
- In
2
)
=
( 50
2
- 30
2
)
= 114 seconds
The application can work at 50 Amps for 114 seconds before the Alarm 11 is
activated.
RATED CURRENT
F17= ## A
DEFAULT: 25
MIN: 0
MAX: 40
OVERLOAD TIME
F18= ### s
DEFAULT: 60
MIN: 0
MAX: 60
