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Post by clyevo on May 8, 2015 13:28:27 GMT
Can i use 6 pole AC motor for this project? Advantage: - lower speed thus less noisy than the conventional 4 pole - better torque -> uses lower gearbox ratio -> better efficiency gearbox
Disadvantage: -bigger and heavier motor -need bigger gearbox size and heavier -more expensive
Did i miss anything like "duh, AMC1280 doesn't work with 6 pole AC motor" or anything at all to why i should not use 6 pole?
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Post by tronicgr on May 8, 2015 16:01:09 GMT
As long you can reverse its direction with the vfd, you can use it.
Can these be driven by usual vfd inverters (3phase)?
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Post by clyevo on May 8, 2015 16:04:47 GMT
As long you can reverse its direction with the vfd, you can use it. Can these be driven by usual vfd inverters (3phase)? how do i find out if it can or not? it is AC asynchronous motor sorry for the big size
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Post by vicpopo on May 8, 2015 19:11:42 GMT
The question is why do you want to use a 6 poles because with the inverter you can set the speed you want . Did you have better torque ? Usually 6 pole are more expensive as 4 pole ! Can you explain what would be your interest buying 6 pole motors?
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Post by clyevo on May 9, 2015 7:30:04 GMT
The question is why do you want to use a 6 poles because with the inverter you can set the speed you want . Did you have better torque ? Usually 6 pole are more expensive as 4 pole ! Can you explain what would be your interest buying 6 pole motors? Advantage: - lower speed thus less noisy than the conventional 4 pole - better torque -> uses lower gearbox ratio -> better efficiency gearbox - gearbox that is big frame and lower ratio has better service factor Disadvantage: -bigger and heavier motor -need bigger gearbox size and heavier -more expensive "Using a VFD, with fundamental frequency being reduced to achieve lower speed, the voltage also is reduced in direct proportion to the speed reduction. As mentioned earlier, a 460V motor at half rotor speed will have 230V across its lines. Thus, if the motor's rating is 100 hp at full speed, its output would only be 50 hp at half speed." more explanation here ~linkAnyway, 8 pole motor torque would be doubled compare to the same power 4 pole motor as we can see below: EDIT : but the gearbox ratio will make up for this torque but still it does has advantages T = 9550 P/n where T = rated torque (Nm) P = rated power (kW) n = rated rotational speed (rpm) <- would be lower direct proportionate to number of poles
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Post by vicpopo on May 9, 2015 7:53:54 GMT
Hi Clyevo,
In the datasheet I tried to compare a 4 pole motor 0,55 kW to a 6 pole 0,55 kW.Sorry but the advantages you mentionned above spring not to my eyes clearly ! ;-) The don't mention the rated torque at nominal speed ! Difficult to compare without this data. Anyway in my opinion if you have to spare money you can spare it to the motor because asynchronous motors are the most common motors in the world . But don't spare money with inverters. A good motor with a poor inverter it's a pitty A not so good motor with a great inverter ( VFC control but a real with a auto tune program to measure coil inductance , resistort etc to build the model to control it) that the best way !
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Post by clyevo on May 9, 2015 14:44:20 GMT
You can calculate the rated torque from the formula i given above but that is at 100% efficiency which is unlikely in real life This one got display rated torque www.aliexpress.com/store/product/AC-3-phase-motor-B5-B14-B34-Aluminum-shell-motor-MS-90L-4-2HP-1-5KW/1490643_32275877246.htmlYeah, you are right about that, motor are easy to replace. Actually i am still more likely to buy a 2hp 4 pole motor with 60:1 gearbox because this is cheapest for me. Just nice to have someone opinion on why 6 pole are rarely used in this 6dof projects. When i saw videos from DIY project using 1400rpm motor, i can hear that loud motor noise so i just thought maybe using higher pole motor can solve this noise problem.
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Post by vicpopo on May 9, 2015 18:03:30 GMT
Jérôme who had created this blog builded his 6dof with 6 pole motors I believe. Below the link for his blog because he coreated also the vr system for'the occulus rift. www.vectionvr.com
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Post by clyevo on May 10, 2015 8:44:09 GMT
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Post by vicpopo on May 10, 2015 12:16:40 GMT
Hi Clyevo,
The sound you can hear comes also from Inverter PWM signal.My setup is a PWM at 4 kHz .I could setup this parameter to higher values as 8 kHz , 12 kHz or 16 kHz which could reduce this noise. But a so high PWM signal could decrease the inverter performance and we need the full Inverter performance ( high ramp up and down , change directions continuously). And when driving the car with a great sound system , you forget this unfair noise !
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