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i am doing a new installation of a 2 speed motor. 5.5kw/7.5kw
i think both windings are internally connected star,so i it should be 2 contactors for slow and fast.
my question is ,should you use 2 overload relays as the current is different in each speed?
Can you give the exact make and model number of the motor? Is it definately wound with two sets of three windings for the two speeds? I'm not sure how this arrangement would work TBH, the rotatonal speed of a 3-phase motor is determined by the number of poles in the windings and I'm not sure if you can have a motor that's wound for example as 4 pole and 6 pole at the same time. Are you sure it's not just a standard wound motor that has the option to be wired in star or delta depending on the application? Without more info I would risk advising on overload protection.
There is such a thing as a dual speed induction machine. I just can not recall the name for it. By switching the connections to the windings, the stator changes from a 2 pole to a 4 pole machine.
Not very common, but is available.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide! Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide! Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
It's possible in theory so I've no doubt some lunatic somewhere will be making them but I've never seen one. If it was a 2-pole and 4-pole arrangement within a single stator then you could be looking at 16 winding wires on the connection termination block. Rather you than me connecting and commissioning Bergie
The Dahlander motor is a a reality, you can order from your local motor supplier.They may not know what you are talking about, but if they are worth their salt they will.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide! Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
i've encountered them a few times ,but fortunately in this application it would be internally connected star. now to find it in EXD . the cheapest i found so far is about R 45000 ex vat for a 5.5kw.
we have been waiting patiently all these years to see andy get stumped.
A VSD would be far cheaper, and just as effective. If the client wishes to have 2 speeds only, and is not keen on a potentiometer, then get 2 potentiometers, which are set for the 2 speeds he requires and use a switch to select the pot for the speed required.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide! Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
problem is its on portable pumps in hazardous areas. the vsd would have to go inside an ex box which is sealed,but the vsd needs air for cooling. the vsd cant be installed outside the haz area as the pump is portable.
we have been waiting patiently all these years to see andy get stumped.
TBH It's not that rare, I get stumped quite regularly. I've never worked on a Dahlander Motor installation but I live in hope.
You can fully enclose a VFD in an enclosure without ventilation but there strict manufacturer recomendations on how much surface area the enclosure must have to allow the heat to be dissipated and it must be of metal construction. The enclosure size is also relative to external ambient temperatures so if it's being used outdoors in a ventilated and shaded area then it should be a sensible size. The last drives we had to fully enclose in a plant room (44 degrees C ambient) the enclosure needed to be 1000 x 1200 x 500mm and mounted on spacers to hold it off the wall in order to fulfil the heat dissipation requirements. We also installed a small tangential blower similar to an air curtain above them just to play it safe.
so the enclosure for the drive would be a bit big for a portable pump on a trolley. not to mention the exd enclosure would also cost a fortune.
But Bergie the enclosure along with the VSD would be far cheaper than the R45K you mentioned in one of your posts. Being portable, does this not make the extension a challenge to maintain in a hazardous area?
If it is variable pumping output you require, then a loop back valve system may be a cheaper solution with a single speed motor.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide! Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
i think the enclosure for the vsd would be too big and impractical. the customer can decide,they have big budgets. their mechanical engineer doesnt have an easy mechanical solution either.
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