Thermal Overload Protection - ABB HF Series Manual

27 E L E C T R O N I C C O M PA C T S TA R T E R | M A N U A L
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4.1

Thermal overload protection

The electronic compact starter to protect three-phase motors against overload.
If the current exceeds the set value – see chapter 3.3 for setting the nominal current – the motor starter trips with class 10A
within the specified tripping time.
The following figure 18 shows the tripping characteristics for 20°C ambient temperature, tripping class 10A. The overload
current factor is the ratio between the actual current and the parameterized nominal current.
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18 Tripping characteristics class 10A
As soon as the electronic compact starter detects an error:
• The feedback relay is activated: the NO (95-96) contact is closed or the NC (96-97) contact is opened.
• The LEDs provide visual confirmation of the error (Please see chapter 4.4 for diagnostics)
If the current exceeds 45 A for more than two sec., the electronic compact starter will switch off the motor. The trip will be
indicated through the LED and the switchover contact will be switched. This functions protects against stall and jam.
Function principle: thermal calculation method
The electronics continuously calculate a model of the thermal load on the motor, dependent on operating time and load
current. The motor memory module charges when the motor is switched on, and discharges by switching off the motor.
After an overload trip, the motor memory module is discharged after two minutes. You have to wait for this cooling time to
elapse before you can proceed with a manual reset. If the control supply voltage fails, the HF-starter stores the remaining
cooling time. When the control supply voltage is restored, the remaining cooling time elapses before the motor can be
switched on again. Otherwise automatic reset takes place after 20 minutes.
When initiating a restart very shortly after switching off the motor, the motor memory module may not yet have fully
discharged. This can result in an overload trip after restarting. During continuous operation, tripping times are reduced
depending on the prior load.
If supply and control voltage are present after resetting the overload trip, the electronic compact starter restarts.