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Star-Delta Starting
Technical Data
When starting:
- inrush current reduced third direct starting current,
- motor torque reduced third even less direct starting torque.. much higher than the resistive torque order reach
sufficient high speed when the motor connected star.
The motor must constructed with terminal windings.. Countdown programmed starting time (normally then begins. This system can used all the squirrel cage motors,
which are normally used delta connection. Its usual designation «400 690 motor».
Exam ple: motor for 400 star-delta starting must designed for 400 «delta» connection.
3rd stage «Delta» connection transition time (or dwelling time) fixed between opening the «star» contactor and closing of
the «delta» contactor the use TE5S timer. contactor delta con
tactor, the use tim including dwelling tim (or transition time) e..
In this type starting, recommended choose motors having high starting torque i.
This starting mode therefore ideal for machines having low starting
torque such as:
- pumps,
- centrifugal compressors,
- wood-working machines, etc. TE5S not recommended.
5
1SBC101001C0202
.
Transient current generated when switching from star delta connec
tion.
2nd stage «Star» «Delta» switching When the programmed starting time over, the KM2 «star» contactor opens.
Respect the following conditions enables utilization the starter without excessive
overheating the connections nuisance tripping the thermal O/L relay. timer set for the starting duration star
connection enough.e.
Maximum duty per the chart side.
(Switching frequency/hour, according acceleration time and load factor)....
Note:
When . mainly the decreasing rotation speed acceptable during the starting phase.
In order prevent high current peak, least nominal speed
must reached before switching from star delta. contactor star contactor with .
An electrical interlock between star and delta mandatory such through auxiliary contacts.
Utilization
During the initial starting phase («star» connection), the resistive torque
of the driven load must remain, irrespective speed, less than the «star»
motor torque until «star-delta» switching occurs. This prevents short circuit between «star» and «delta». contactor types are used delta and star contactors . The KM1 «line» contactor then
closes and the motor starts.
Furthermore, open transition, the current interruption may reach ms: shall checked that this duration compatible with the ap
plication i.e.
Precautions
M otor nominal voltage delta connection must equal that the mains.g.
Sequence
Starting three-stage process:
1st stage «Star» connection Press the «On» button the control circuit close the KM2 «star» contactor.
Example:
- Switching frequency sta rts/h r
- Acceleration time "ta" (use curve)
- Maximum load factor %
This corresponds 4-minute operating cycle (15 starts/hr) with seconds acceleration,
2 minutes operation and minutes rest.General Inform ation
Star-Delta Starting
of Three-Phase Asynchonous Motors
General
Star-delta starting the most common method reduce the starting current motor
