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B

BIGEYE

Hi All,
Here is the scenario that I have.
3 Phase, 690 Volt Motor (Delta), 560 kW and started by a star-delta starter. So the motor is connected in delta at full voltage 690 Volts after the chageover from star.
Now, this motor has failed and is beyond repair, and lead time is considerable for this size of motor.
We have a 690 Volt motor spare, but it is a star connection at 690 Volts. It has been suggested that we can connect this motor in star and run it with an inverter.
Can anyone see any problems with this, or offer any alternative?

TIA
 
560KW is this correct and may i ask what the motor is doing as this is one big beast if i read correctly, is the replacement motor a duel voltage i take it with delta rated for say 440v and what is you local supply voltage phase to phase just to confirm what you have written.
 
560 kW, 690 Volt, Delta is the correct rating and it drives low pressure high volume air blower. The replacement motor is 690 Volt Star connection, no indication on the nameplate if 440 Volt Delta rated but I suspect that it would be, as most duel voltage motors are 440 Delta/690 Star.

Our supply voltage on this MCC is 690 Volts and is supplies by 2 x 11kV/690V, 3 MVA transformers in parallel.

The failed motor is wound for 690 Volt Delta operation, that is why it is started by Star-Delta starter, and such a long lead time. Also costs around £30k.
So all the info I have given is correct.
 
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Well think with a motor of this size i would be supprised if anyone has experience of such a beast and with a extended run up time i think this will be for a specialist in this field to advice on, i would pick out a popular VSD brand and consult with technical as this motor would go beyond the experience of most if not all on this forum including me, i would be interested of your findings though but wouldnt be supprised if technical arranged a site visit with design team to help you, i can only imagine if they do an inverter it would be like a shed :O.
 
So long as the other motor has a rated power sufficient to drive the air mover then it could be used without any real issue, providing that the starter is suitably modified, and al the associated equipment including starter and cabling is capable of running at the now increased currents. Your drive is at what I would normally consider the normal practical limits of an LV motor and realistically you want to be consulting with a qualified engineer before carrying out these changes.

The VSD is an option, but again only if the other motor and equipment is capable of supplying it safely. 550 kW is just inside the range of the ABB ACS800-02 VSD units ( see ABB VSD Cabinets, page 12). We have just fitted a 330kW version of one of these, and believe me this cabinet is small - about 0.75m * 1m *2m (W*D*H), probably a lot smaller than your existing starter unit.

ABB are by far the best known of the VSD manufacturers, but also one of the most expensive. There are others out there, but possibly ABB's strong-point would be the ability to deliver both VSD and motor as a package.

The VSD will not be a cheap option in the short term, but when you factor in things such as reduced starting currents (~ rated motor amps) which could well cut your metering charge per kVA of maximum demand by a significant sum, the reduced stresses on the equipment and therefore better reliability, then in the long term the VSD option may well pay for itself pretty soon. Again speak to the experts.
 
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I would consult with an engineer. If you run the motor in star your output torque could be drastically reduced and depending on the load the motor may run in stall and not reach full speed. It could be down to the type of impeller on the fan, if it's backward curved you might get away with it but with an axial you might not. If this is the case your motor will efficiency will be reduced and your power factor will also suffer.

The decision you're making should be based on some fairly complex motor calculations which are best made by a specialist.
 
We have done up to 800Volts and up to 1MW motors and drives

Yes, its very possible to do but would need a bit more info on what you have exactly

Ball park for an 890PX SSD Drive is £48K and thats a floor standing rittal cubicle 2.2mtrs wide with 2 x parallel air cooled stacks all switch gear and MCCB, 690VAC 600KW Constant torque at 663Amps (12 weeks delivery)

Parker SSD AC890PX Modular AC Drive

And no i dont work for SSD but have fitted their drives for over 25 years now

Regards

Canoe
 
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