Hi, let's say that I have this hypothetical motor that is rated for
24V DC and draws an unknown amount of current (say around 1A).Input is 230V AC.
I'm wondering if the motor will work properly with a step-down transformer to 24V AC and a rectifier but no smoothing.
Is that going to make it noisy or break it in the long run?
Thanks.
No, as long as the output of the rectifier is 24VRMS. It might have a bit of 120HZ hum (I'm assuming a full-wave rectifier), but the motor itself has a lot of inductance, which sort of makes it its own filter.
Hope This Helps! Rich
Yes, thanks!
-- Foo
If its just a commutated brush type motor, it should work fine.
Firstly, a transformer will deal with voltage level and isolation from the AC line, but it'll cost you. A 230VAC motor might be a cheaper way to go. The transformer can be 48V center-tapped, with two diodes, or
24V with a bridge of four diodes.The nominal "24VDC" rating probably means anything from 18V to 28V is acceptable. If you don't know the current requirement, DO include a fuse. Transformers are often made short-circuit-safe with fusible wire, and burning out the transformer makes for one expensive bit of experience, but a fivepak of fuses gives you that experience several times, for the cost of a candy bar.
Beware. The operational current to drive a 24V/24W motor wil be about 1A as you might expect. The inrush current however will be a multiple of that 1A and your rectifier should be able to handle that current. A 10A full bridge rectifier is no overkill.
petrus bitbyter
Unfortunately, I don't think this motor can be replaced.
I didn't include this in my first post, but was actually thinking about such a transformer _and_ a four diodes bridge to allow reverse operation of the motor with a two-way switch.
Thanks for the tip. Maybe a fuse on the 230V side is a good idea too?
-- Foo
Yes, but size it such that it won't blow unless there's a transformer failure. IOW, the fuse on the motor side should blow first.
Hope This Helps! Rich
Also, that's what "Slo-blo" fuses are for.
Cheers! Rich
r
I think it work properly as long as load on dc motor low.
Thanks for your replies.
Now, if I happen to add a capacitor to smooth the DC output somewhat, do I need to replace my transformer with one that outputs 18V instead, or will the voltage drop take care of that?
Which setup would you recommend? My goal is to keep this circuit as simple and efficient as possible. I'm willing to add a capacitor if it improves efficiency.
-- Foo
-- Since 24VRMS is about 34V peak, DC, adding a capacitor will cause the input of the motor to rise to 34V if capacitor is large enough. I\'d stick with a full-wave bridge and no cap.
Okay. One last question: for a 25W motor, is a 30VA transformer appropriately sized?
-- Foo
Yes, with the full-wave bridge and NO capacitor.
Cheers! Rich
Thanks!
-- Foo
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