Page 952 - ABB_Motor _Protection_and_Control_catalogue_20221216

13/62 ABB MOTOR PROTECTION AND CONTROL

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Star-delta starters protected by overload relays
With AF contactors - Open type version in kit form

Application
Star-delta starting is the most common method to reduce the starting current of a motor.
L Y
This system can be used on all the squirrel cage motors, which are normally used in delta
connection. In this type of starting, it is recommended to choose motors having high start-
ing torque i.e. much higher than the resistive torque in order to reach sufficient high speed
when the motor is connected in star.

I /In T /Tn When starting:
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• Inrush current is reduced to a third of direct
6 I (delta) starting current
1SFC101103V0001 5 • Motor torque is reduced to a third or even less
of direct starting torque.
Transient current is generated when switching
4
from star to delta connection.
3
During the initial starting phase ("star" connec-
2 T∆ (motor) tion), the resistive torque of the driven load must
I (star)
AF16-30-10 + AF16-30-10 + 1 remain, irrespective of speed, less than the
AF09-30-10 + BEY16-4 + VEM4 + TF42 T (motor) "star" motor torque until "star-delta" switching
Tr (resistive torque) occurs.
0 20 40 60 80 100
Motor speed (%) This starting mode is therefore ideal for ma-
I = current In = nominal current chines having high starting torque such as
T = torque Tn = nominal torque pumps, centrifugal compressors, wood-working
machines...

1SFC101104V0001 Precaution
• Motor nominal voltage in delta connection must be equal to that of the mains. Example: a
motor for 400 V star-delta starting must be designed for 400 V in "delta" connection. Its
usual designation is "400 V / 690 V motor". The motor must be constructed with 6 terminal
windings
• In order to prevent a high current peak, at least 85 % of nominal speed must be reached be-
fore switching from star to delta

Sequence
AF140-30-11 + AF140-30-11 + Starting is a three-stage process:
AF140-30-11 + BEY140-4 + VM19 + EF146
1st stage: "Star" connection - Press the "On" button on the control circuit to close the KM2
"Star" contactor. The KM1 "line" contactor then closes and the motor starts.
Countdown of programmed starting time (6 to 10 s) then begins.
2nd stage: "Star" to "Delta" switching - when programmed starting time is over, the KM2
"Star" contactor opens.
3rd stage: "Delta" connection - Thanks to AF contactors, a transition time (or dwelling time)
of 50 ms is already integrated between the opening of the "star" contactor and
closing of the "delta" contactor.
Conclusion: An on-delay timer without dwelling time (e.g.: CT-ERS.21S or TEF4-ON) is
enough to countdown the programmed starting time (6 to 10 s) during "Star connection".
The use of a star-delta timer including a dwelling time is not permitted.
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Main Technical Data
Mounting positions Standards IEC 60947-4-1 / EN 60947-4-1
Rated operational voltage Ue max. 690 V - 50/60 Hz
Rated insulation voltage Ui
acc. to IEC 60947-4-1 690 V
acc. to UL / CSA 600 V
Ambient air temperature
Close to the device ≤ 60 °C (TF42: 38 A above ≤ 50 °C)
Degree of protection IP20
Switching frequency Refer to "Switching frequency diagrams" page
Pos. 1