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Best / cheapest way to slow down motor RPM by fixed amount

platypus117

Plastic
Joined
Sep 11, 2019
We have a small 3 phase conveyor (0.17kW, 5A) in our warehouse which was bought for a role which required a fairly high speed, but now we would like to re-use it in a different place where it would need to run about 30% slower.

I have succeeded in lowering the speed correctly using a (rather expensive) VFD from Schneider that I had available, and which can do all sorts of other things that are useless in this context.

My question is - has anyone an idea on how to do this in a cheaper way ? I just need to slow the conveyor down by a fixed amount, and then it will never need to change, so basically I don't need about 99.9% of the features in a typical (even low end) VFD :(

Thanks in advance !
 
Pre-VFDs, the solution would have been a simple gearbox. If the VFD solution is working for you (i.e., not running into torque limitations), that's almost certainly the cheapest current solution.

Keep in mind that VFDs (at least in the low-feature tier) are so cheap, people are using them as point-application single-to-three phase convertors. Basically using none of the VFD control features.
 
Although I agree that a VFD is likely a CHEAPER way to change speed on a DIRECT DRIVE situation, if there is any sort of belt / chain drive involved already, simply changing the sheave / sprocket ratio is usually less expensive. You didn't really say how your conveyor is powered.

One thing to understand however is that when you lower the speed via mechanical means, you INCREASE the torque. That can be beneficial in conveyor situations. With a VFD, the BEST you can hope for is to not LOSE torque when lowering speed. So if, by decreasing the speed, you increase friction / sticktion, or if that results in MORE product being dumped onto the entire conveyor length, that increased torque might be a necessity.
 








 
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