jraef Posted April 12, 2007 Report Share Posted April 12, 2007 OK, this is a new one on me. I recently was involved in a proposal to supply contactors for star-delta motor starting on elevators. In the proposal, the starter samples were a pair of mechanically linked contactors with bridging bars on the load side, and a shorting bar across 3 terminals on the line side of one of them. I was under the impression that these were simply 2 of the 3 contactors and that the user just wanted to see how we accomplished the mechanical interlocking and didn't need to see the entire starter, but when they showed me their finished product (using another brand), I saw that these were the ONLY contactors used! I wasn't allowed to take pictures or look at a schematic, but for the life of me I cannot figure out how they are able to do star delta starting with only 2 contactors! When I asked someone to explain it, I was told " Don't bother trying to figure it out, that is how the elevator industry has done it for years". Anyone familiar with this? "He's not dead, he's just pinin' for the fjords!" Link to comment Share on other sites More sharing options...
GGOSS Posted April 12, 2007 Report Share Posted April 12, 2007 Don't have an immediate answer for you but will give it some thought. The elevator industry have been doing what may would perceive to be 'strange' things for years. An example includes 6 wire connected soft starters with a single isolation contactor connected inside the delta loop. Regards, GGOSS Link to comment Share on other sites More sharing options...
marke Posted April 12, 2007 Report Share Posted April 12, 2007 I suspect that it is a dual speed rather than a star delta, i.e. a delta / double star. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
jraef Posted April 13, 2007 Author Report Share Posted April 13, 2007 I suspect that it is a dual speed rather than a star delta, i.e. a delta / double star. Best regards, Ahhhh, maybe that's at the core of this, it isn't a typical star-delta motor. I know they are not using it as 2 speed, but maybe they are starting it that way in order to save on having that 3rd contactor. I am getting more info on this next week, I'll let you know what I find out. "He's not dead, he's just pinin' for the fjords!" Link to comment Share on other sites More sharing options...
marke Posted April 13, 2007 Report Share Posted April 13, 2007 Hi Jraef Two speed motors are used on elevators to reduce the jerk at start and the jerk at stop. - just one of the many possibilities. As an alternaive, could it be like a part winding starter with parallel star windings, and on the second star, opening the star point rather than switching phase to the motor. makes it harder to get it wrong. Three live wires to the motor and three star wires. With a part winding, things get embarasing if you mix the phases between the two part windings. - just a thought, but you are correct, things are done differently in the elevator industry. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
marke Posted April 17, 2007 Report Share Posted April 17, 2007 Another thought is to just eliminate the main contactor, leave the start ends of the three windings permanently connected to the supply, and have the two contactors connected to the finishes of the windings, and switch these for delta or star. Both open, motor stops. Just dont put your fingers in the terminal box!!, and too bad if a winding goes to earth. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
jraef Posted April 19, 2007 Author Report Share Posted April 19, 2007 Another thought is to just eliminate the main contactor, leave the start ends of the three windings permanently connected to the supply, and have the two contactors connected to the finishes of the windings, and switch these for delta or star. Both open, motor stops. Just dont put your fingers in the terminal box!!, and too bad if a winding goes to earth. Best regards, I think you may have hit the mark, Mark I'm going over to visit again tomorrow and find out. I'll keep you apprised. "He's not dead, he's just pinin' for the fjords!" Link to comment Share on other sites More sharing options...
jraef Posted April 24, 2007 Author Report Share Posted April 24, 2007 You were dead on Mark! The circuit consists of 3 line terminal blocks labeled L1.2.3, which are directly jumpered to 3 motor terminal blocks labeled T1,2,3! Then the T4,5,6 leads to the motor are connected to a common jumper between the Delta and Star contactors. I asked about the inherent danger of the motors being connected at all times, they understand the issues and state that the technicians in that industry are used to it. "He's not dead, he's just pinin' for the fjords!" Link to comment Share on other sites More sharing options...
medo_ibiza Posted May 17, 2007 Report Share Posted May 17, 2007 so it's not a new idea or a new way to implement the star delta starter as you say. it's just that they reduced the cost of the system without eleminating the danger rising from its absence. if you please let me know if am wrong or right. thanks Link to comment Share on other sites More sharing options...
marke Posted May 17, 2007 Report Share Posted May 17, 2007 Hello medo_ibiza That is correct. I would not recommend this practice and believe that in many countries, it would be illegal as the starter can not remove the live conductors from the motor as required. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
jraef Posted May 18, 2007 Author Report Share Posted May 18, 2007 I agree. In subsequent discussions with them, it came to light that average electricians are not allowed to work on elevator controls; it takes a special license to do so. So in that aspect, the elevator technicians are all going to be trained on this methodology and understand the implications. An interesting side note to that however. I am now starting to do training for some of the technicians and when I mentioned that this was a non-standard way of doing it, none of them were aware of that! They had no idea that standard Y-Delta controllers have 3 contactors; they wanted to know what the 3rd one was for! "He's not dead, he's just pinin' for the fjords!" Link to comment Share on other sites More sharing options...
epsngr Posted July 31, 2007 Report Share Posted July 31, 2007 Jraef Do you have any sketch of the two contactor connection. I like to see the a bit graphically. I am still strugling with clear operation of the star delta. The designs I have found are not explained correctly. Any idea of any star delta with clear explanation of the sequence of operation of the contactors? Link to comment Share on other sites More sharing options...
marke Posted July 31, 2007 Report Share Posted July 31, 2007 Hello epsngr For an explanation of star delta starters, see http://www.lmphotonics.com/star_delta.htm The two contactor version referred to, has KM3 replaced with links, i.e. KM3 removed. This would not be satisfactory in most applications as the motor becomes permanently connected to the supply. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
epsngr Posted July 31, 2007 Report Share Posted July 31, 2007 I have seen it. The drawing is ok to me. The operation is not. I take it that on when the push button is pressed, current flows through the timer, KM1 & KM3. After a set time K1T operates and K1 opens while K2 operates but K3 remains on. If this is correct, does this happen so fast before the push button is released such that K2 holds and allow the current path to be maintained? Link to comment Share on other sites More sharing options...
marke Posted July 31, 2007 Report Share Posted July 31, 2007 Hello epsngr I am sorry, there is an error in the control diagram, the hold in contact (across the start button) labeled k2, should in fact be labeled KM3. I must find the original and correct it!! Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
jraef Posted August 1, 2007 Author Report Share Posted August 1, 2007 LOL, never noticed that! "He's not dead, he's just pinin' for the fjords!" Link to comment Share on other sites More sharing options...
kens Posted August 1, 2007 Report Share Posted August 1, 2007 To Quote Jimi Hendrix " You can't believe everything you see and hear now, can you?" Well spotted epsngr An expert is one who knows more and more about less and less until he knows absolutely everything about nothing Link to comment Share on other sites More sharing options...
marke Posted August 7, 2007 Report Share Posted August 7, 2007 OK Drawing is now corrected. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
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