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Thread: Star delta
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09-10-2009, 08:52 AM #1
Star delta
Can some one help me with star delta? Like explain it to me. Thanks
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09-10-2009, 10:00 AM #2
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09-10-2009, 01:56 PM #3
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Re: Star delta
In3 phase motor we have different type of wiring inside of motor (if RPM is changed we have different of wiring inside motor and also each type of motor has own one ) but all of them has 3 in and 3 out(( 3 wiring inside ))
L1 - L2 - L3 In and L4 - L5 - L6 out---L1 and L4 is one wiring L2and L5another one L3 and L6 another one
((also in some countries they say U –V – W with X – Y – Z ))
in box you see U V W OR L1 L2 L3
Z X Y L6 L4 L5
our lines is (R-S-T ) and L1 + L2+ L3 is our in to motor if we connect L4+L5+L6 ((X-Y – Z)) with together we have star wiring or if we do R ( L1 + L6 or U - Z )-S ( L2 + L4 or V - X ) –T ( L3 + L5 or W - Y ) we have delta Wiring
Some compressor has 2 ((3 wiring inside motor ))and they use L1 - L2 - L3-(( L4 - L5 - L6 they connect in inside motor and we cannot see in box)) L7 – L8 – L9 and also L10 – L11 – L12 (( L10 – L1 – L12 they connect in inside motor and we cannot see in box)) this wiring is called 2 star wiring motor mainly L1 - L2 - L3 are main wiring for star or fist one come to load and L7 – L8 – L9 are second wiring starLast edited by mbc; 10-10-2009 at 06:54 AM.
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09-10-2009, 02:38 PM #4
Re: Star delta
hi mbc u wrote what it is but not what it does !! the idea is to start a big motor with a amaller inrush current thus avoiding tripping overloads and damage to the motor when u start a motor by star and then transit to delta ( make sure motor is fit for this )
u basicly are using a lower amperage and then going to the higher one only by meanes of changing your motor leads today however it is much cheaper and better to use soft starting check the net for rvs starters by siemens solcon allen bradley
good luck
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09-10-2009, 07:26 PM #5
Re: Star delta
Or, using the power of Google you could have found this...
http://www.patchn.com/index.php?opti...d=42&Itemid=74Brian - Newton Abbot, Devon, UK
Retired March 2015
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09-10-2009, 08:11 PM #6
Re: Star delta
I need to know how it works what it is my engineer explained it to me but it flew write over my head. Need it explained to me 2or 3 times then im a genious at it! he said if i dont know star delta i should go flip burgers haha
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09-10-2009, 08:30 PM #7
Re: Star delta
OK, basically you can start a big electric motor in STAR wiring which brings the motor up to speed but cannot maintain that speed with any load on it.
The STAR circuit is dropped out as the DELTA circuit is switched in.
The DELTA will then maintain the motor speed with load.
At STAR start the amperage will quickly peak and then drop back; it is at that point that you can change over to the DELTA circuit.Brian - Newton Abbot, Devon, UK
Retired March 2015
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09-10-2009, 11:15 PM #8
Re: Star delta
Hi Lets start with STAR, you have 3 windings (when stopped think of them as 3 heater elements) when they are connected in star the middle point is like a neutral (in the old days some actually fitted a neutral here) so the voltage going to each heater is 240V (UK) so at this point (only) you can use ohms law V=IR. So if you check your compressor winding resistence (R) you can calculate your inrush current (simply) for example V =240 R=1 so amps would be 240/1= 240amps in-rush.
Delta when the 3 windings are connected in delta you have 415V across each winding so using the same calculation.
415/1 = 415amps inrush.
So you can see that your starting current is much less in star.
(remember when the motor is running you can not use simple ohms law)
"As a side not, very early on in my apprentaship, I condemmed every compressor I came across, because they seemed to be a near dead short"
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10-10-2009, 12:20 AM #9
Re: Star delta
Deano
An over veiw explanation of star delta starters is a low voltage start, and high voltage run. To reduce amp inrush at start. The power supply people do not like high amp inrush users on the power network, they create power spikes and voltage problems.
So STAR gives a low voltage motor coil connection, and DELTA gives a high voltage motor coil connection.
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