Could anyone advise which reputable motor manufacturer (worldwide) has a capability to build inverter duty induction motor with the following major parameters: Rated Power 1000 HP, Rated Torque 3000 ft-lb, Base Speed 1750 RPM, Top speed 6000 RPM, Max voltage 690V? We've already got negative responses from ABB and GE.
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Help to find a motor supplier 1
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BrianPetersen
Mechanical
I've never seen an ordinary-ish induction motor that big which is capable of spinning that fast.
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- #4
The reason for negative responses probably is low voltage for such a high HP rating .
Turns per coil could be fractional and very small, something like 0,3 or 0,6 and could be impossible to find the proper winding arrangement , despite the max. number of circuits.
MV or HV motor should be used instead.
Winding Design
Turns per coil could be fractional and very small, something like 0,3 or 0,6 and could be impossible to find the proper winding arrangement , despite the max. number of circuits.
MV or HV motor should be used instead.
Winding Design
LionelHutz
Electrical
So, you really want a 3333hp, 6000rpm, 2300V, 200Hz motor?
You'll need a 2300V drive if you expect to maintain torque up to 6000rpm.
I'd suggest you go to the suppliers and ask for a motor and drive combination capable of doing what you want instead of trying to fit a motor into a drive.
You'll need a 2300V drive if you expect to maintain torque up to 6000rpm.
I'd suggest you go to the suppliers and ask for a motor and drive combination capable of doing what you want instead of trying to fit a motor into a drive.
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- #8
Thanks for good tip, ScottyUK. For all major suppliers we contacted, the show stopper was a top speed 6000RPM. And only Siemens confirmed that this motor could be built (at 690V). I do realize that for this HP rating the MV would be preferable, but the end user insisted on lower voltage design. Thanks to everybody for comments.
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1
- #9
LionelHutz
Electrical
I doubt you are specifying the motor correctly. You have to be careful of the V/Hz ratio when specifying a motor that is being run over it's base frequency.
If you buy a 690V, 1800rpm motor and run it at 690V, 6000rpm then you would theoretically have 875ft-lbs of torque at 6000rpm. But, I doubt reality would match that theory and the actual torque will be much lower. But, if you really only need 875ft-lbs of torque then buy a 300hp, 1800rpm, 208V motor and use it with the VFD set for a base frequency of 200hz @ 690V.
If you expect to maintain 3000 ft-lbs of torque up to 6000rpm then you will need the 2300V VFD operating that 690V motor. The base frequency setting in the VFD would be 200hz at a motor voltage of 2300V.
If you buy a 690V, 1800rpm motor and run it at 690V, 6000rpm then you would theoretically have 875ft-lbs of torque at 6000rpm. But, I doubt reality would match that theory and the actual torque will be much lower. But, if you really only need 875ft-lbs of torque then buy a 300hp, 1800rpm, 208V motor and use it with the VFD set for a base frequency of 200hz @ 690V.
If you expect to maintain 3000 ft-lbs of torque up to 6000rpm then you will need the 2300V VFD operating that 690V motor. The base frequency setting in the VFD would be 200hz at a motor voltage of 2300V.
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- #10
With a motor that large centrifugal forces may be the limiting factor.
If you can find a motor that will take the mechanical stress, follow Lionel's suggestion sort of and have it wound for 208 Volts.
If each 690 Volt winding is divided into 3 sections that are then connected in parallel, the rating should be 201 Volts.
Set the base voltage to 201 Volts.
The power at 6000 RPM will be 1000 HP x 1750 RPM / 6000 RPM = 3429 HP
As long as you are able to maintain the Volts per Hertz ratio, the HP will be proportional to the speed.
Or you could use a 300 HP motor for 300 HP at 1750 RPM and 1028 HP at 6000 RPM.
If you use a 690 Volt, 1750 RPM motor all the way up to 6000 RPM, the Volts per hertz ratio will be dropping and the HP will remain constant at rated HP above rated frequency and speed.
Bill
--------------------
"Why not the best?"
Jimmy Carter
If you can find a motor that will take the mechanical stress, follow Lionel's suggestion sort of and have it wound for 208 Volts.
If each 690 Volt winding is divided into 3 sections that are then connected in parallel, the rating should be 201 Volts.
Set the base voltage to 201 Volts.
The power at 6000 RPM will be 1000 HP x 1750 RPM / 6000 RPM = 3429 HP
As long as you are able to maintain the Volts per Hertz ratio, the HP will be proportional to the speed.
Or you could use a 300 HP motor for 300 HP at 1750 RPM and 1028 HP at 6000 RPM.
If you use a 690 Volt, 1750 RPM motor all the way up to 6000 RPM, the Volts per hertz ratio will be dropping and the HP will remain constant at rated HP above rated frequency and speed.
Bill
--------------------
"Why not the best?"
Jimmy Carter
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- #11
LionelHutz and Waross,
The supplier has confirmed the 1000 HP motor design with "mechanical" base speed 1750 RPM (that gives a required constant torque 3000 lb-ft up to 1750 RPM. Motor rated voltage is 690V, and voltage is equal to 420V at 1750 RPM. The voltage is clamped to max value 690V at the speed 2205 RPM ("electrical" base speed). The constant power (1000 HP) region is confirmed from 1750 RPM up to 6000 RPM without tapering. I honestly do not see any reasons for concern, I cover customer requested performance envelope (torque/power/speed curve). We just need to select the VFD that would provide adequate motor current (steady state and overload) and required range of output fundamental frequency for 4 pole motor. And this is not a problem. Thank you for your comments/calculations, but I see nothing wrong with the motor parameters I described above. BTW, this will be water cooled jacket system.
The supplier has confirmed the 1000 HP motor design with "mechanical" base speed 1750 RPM (that gives a required constant torque 3000 lb-ft up to 1750 RPM. Motor rated voltage is 690V, and voltage is equal to 420V at 1750 RPM. The voltage is clamped to max value 690V at the speed 2205 RPM ("electrical" base speed). The constant power (1000 HP) region is confirmed from 1750 RPM up to 6000 RPM without tapering. I honestly do not see any reasons for concern, I cover customer requested performance envelope (torque/power/speed curve). We just need to select the VFD that would provide adequate motor current (steady state and overload) and required range of output fundamental frequency for 4 pole motor. And this is not a problem. Thank you for your comments/calculations, but I see nothing wrong with the motor parameters I described above. BTW, this will be water cooled jacket system.
GE have bought Converteam, the old GEC Large Machines business. Their range looks like it extends up to some surprisingly high ratings - 35MW at 5000 rpm, 22MW at 10000 rpm. Brochure available at
LionelHutz
Electrical
OK, it just seemed odd to want a constant HP and falling torque to test an engine. Most engines have a fairly broad flat torque curve and a steadily increasing HP curve as the speed increases.
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- #15
One option to is to use two smaller dynamometers in tandem. The smaller machine size should allow a greater maximum speed.
A second option is to change the mechanical advantage between the engine and the dynamometer by changing the gear ratio, roller size, or whatever the drive ratio is. By selecting a dyno base speed of 1750, you are requiring a maximum speed that is too high for a single machine of this rating. For example, if you reduced the base speed to 450rpm then the maximum speed would be reduced to 1542rpm. Of course, by doing this you require the dynamometer to produce 3.88 times more torque but power in still equals power out; it is a matter of finding the combination of mechanical advantage versus dynamometer speed that gives the most effective and economical machine sizes. Keep in mind that the dynamometer base speed can be at any frequency. The 450rpm machine in the example may be a 8 pole machine running at 30hz, a 12 pole machine running at 45hz, or any other combination that best meets base speed and CHP speed requirements.
A second option is to change the mechanical advantage between the engine and the dynamometer by changing the gear ratio, roller size, or whatever the drive ratio is. By selecting a dyno base speed of 1750, you are requiring a maximum speed that is too high for a single machine of this rating. For example, if you reduced the base speed to 450rpm then the maximum speed would be reduced to 1542rpm. Of course, by doing this you require the dynamometer to produce 3.88 times more torque but power in still equals power out; it is a matter of finding the combination of mechanical advantage versus dynamometer speed that gives the most effective and economical machine sizes. Keep in mind that the dynamometer base speed can be at any frequency. The 450rpm machine in the example may be a 8 pole machine running at 30hz, a 12 pole machine running at 45hz, or any other combination that best meets base speed and CHP speed requirements.
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