Is this Electric motor VFD Compatible?

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Old 05-09-19, 06:35 AM
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Is this Electric motor VFD Compatible?

So I need to buy a motor and bring down the speed about 300 RPM

I heard that using a 3 phase motor and a VFD, this is possible.

Would this (see pics) 1,1kW 3 Phase 230/400V Motor with 2845U/min be compatible with your standard VFD?
 
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Old 05-09-19, 06:39 AM
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Cant upload pics because I'm "exceeding my upload quota" ?
 
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Old 05-09-19, 06:42 AM
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Picture may be physically too large or file size too great. How to Insert pictures
 
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Old 05-09-19, 07:07 AM
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This is a side note, but unless you actually need the variable speed feature, a mechanical means of speed reduction is almost always better and cheaper than a VFD.
 
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Old 05-09-19, 10:51 AM
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What mechanical means would you suggest? Pulleys?
I am not very mechanically skilled, so a vfd, though more expensive, seems to be a less complicated option.
 
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Old 05-09-19, 10:52 AM
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I agree with ibpooks that mechanical RPM reduction would very likely be better. With a VFD a constant volts/Hz ratio must be maintained as the frequency is lowered in order to keep the current draw through the motor from increasing above its rated value. Therefore at 300 RPM your motor will be running at around 5Hz but at 1/10 th of the normal voltage. The torque will be unchanged but the horsepower will be 1/10 th of its normal rating (because power is proportional to torque x RPM).
By contrast, with mechanical reduction the motor torque would increase about 10x and horsepower would be relatively unchanged.
If you also need fine adjustments of the RPM then a VFD could be combined with mechanical reduction.
 
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Old 05-09-19, 10:58 AM
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In most cases I would use a gearbox to reduce the output speed. Quite often the motor and gearbox are purchased together but a gearbox can be purchased separately and bolted to the face of the motor.
 
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Old 05-09-19, 11:11 AM
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Agree. If this is just for experimenting I suggest searching Ebay with the search term "gearmotor". Most gearmotors have a higher reduction ratio than you want, but there are probably some out there that will fit your needs.
 
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Old 05-09-19, 11:30 AM
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A member is allotted 10mb of storage. You used that up with your motor pics from a previous thread.
I resized all those pictures and you have most of your storage space available back.
 
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Old 05-09-19, 12:11 PM
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I read this one again and I think we might have misunderstood. Do you want the RPM to decrease by 300 to a final speed of 2500 or decrease to a final speed of 300?

In the first case, a VFD is a reasonable solution. In the second case, a 10:1 pulley set or gear set is the best option as it is too slow for practical use of a VFD.
 
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Old 05-09-19, 04:54 PM
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I would like the final speed to be 300 rpm.

So a gearbox would be more appropriate? Where could I buy one of those?

Do I need a 3 phase motor for that, or does a single phase motor work too?

And is wiring a motor to a gearbox very complicated?
 
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Old 05-09-19, 05:01 PM
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The gearbox bolts to the motor. Just the motor gets wired.

What you choose is based on the job and load you need to power.
Can you tell us what you need to drive ?

The link is just a generic sample..... Ebay gearboxes
 
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Old 05-10-19, 06:26 AM
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For a 300 rpm output you definetely need a gearbox. If you can find motors you can find gearboxes. Just do the searching. Best bet would be to buy a gearmotor that is a motor and gearbox combined together in one package. They are commonly specified by their power, output rpm, shaft size and rotation direction.
 
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Old 05-10-19, 08:48 AM
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But could I buy a gearbox separately and attach it to a 3 phase motor myself?

Are there any helpful sites with more information about attaching gearboxes to motors?
 
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Old 05-10-19, 09:47 AM
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There is nothing special about a 3 phase motor other than the flavor of electricity. Yes, a gearbox can be attached to a 3 phase motor. You can also buy 3 phase gear motors. 3 phase motors and gear motors are commonly used in industry and are about the only option when you get above 5 hp (3kw). A 1 hp (1kw) motor is most commonly found in single phase except in factories and other commercial locations relying heavily on 3 phase power.
 
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Old 05-13-19, 02:08 PM
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So I actually found a 1kW 3 phase gearmotor that does 300rpm (perfect for me). It says on the plate that the motor is a 220/380V motor. The owner, however, says that I'd have to buy a capacitor if I want to run it at 220V. Is this true? Could I not simply wire it for delta connection and run it at 220V without issue that way?

The motor wiring is shown below:
 
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Old 05-13-19, 02:17 PM
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The motor wiring isn't shown..... only the terminal posts. We'd need a wiring diagram.
 
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Old 05-13-19, 08:30 PM
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Do you have a source of 220V three phase power? If you only have single phase then you need a capacitor that's switched in during starting, a rotary converter which uses another 3 phase motor, or a VFD.
 
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Old 05-14-19, 05:26 AM
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Yeah I only have single phase power apparently. So a capacitor is all I need to run this motor at 220V?
 
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Old 05-14-19, 05:32 AM
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If you have single phase power why do you insist on a three phase motor?
 
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Old 05-14-19, 05:46 AM
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Well I originally thought that I would be pairing a three phase motor with a vfd. Fortunately you guys have pointed out that a gearmotor is more appropriate. So I'm no longer insisting on anything.
 
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Old 05-15-19, 07:50 AM
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How does changing the speed with a vfd affect the amperage? Does lowering the rpm increase the amperage being drawn from the power supply?
 
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Old 05-15-19, 01:20 PM
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The VFD lowers its output voltage when it lowers its output frequency to provide lower motor speeds. This keeps the current drawn by the motor relatively unchanged. This is necessary to prevent excess current which would overheat the motor windings and also create magnetic fields that are too strong for the iron laminations in the motor (causing them to "saturate").

The reason for this behavior with motors is that they are inductive not resistive loads. So instead of Ohm's law V=IR, we have V=LdI/dt.
What this means is that the current in an inductor doesn't go up immediately when you apply a voltage to it, but it takes some time to build up. And the more voltage you apply to it the faster the current builds up (and vice versa). But when the VFD puts out a lower frequency the time allowed for the current to grow is longer. Therefore the rate of increase in the current must be reduced by lowering the voltage out of the VFD, so that the current does not get too high.

I hope this provides more clarity and not more confusion ;-)
There are more details involved in AC circuits than what I mentioned in the simplified explanation above, but the basics are there.
 
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Old 05-15-19, 01:29 PM
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Thanks for the info!
Think I know what to do now.
 
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