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Member

Join Date: Jun 2011
Posts: 6

how do i get a 110/120v transfered to 140/150v?

06/25/2011 7:05 PM

Hey all,

I have a 130v dc motor and I'm trying to hook it up to a 110/120v ac wall outlet. I'm aware that I will need a rectifier and from what I understand I will lose about 10% power from the rectifier. So I am trying to figure out how to bring the wattage back up from 108 to 130. I need this to be an inexpensive fix and I'm no electronics expert, but I'm willing to take the time and effort to make this work.

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#1

Re: how do i get a 110/120v transfered to 140/150v?

06/25/2011 7:35 PM

Ok,

How much current (amps) will your motor draw?

When you rectify AC to DC you will in fact have a higher voltage, by my dead reckoning be pretty close to what you want.

Most power supply authorities dislike intensely people merely whacking on rectifiers straight onto the mains supply. You will need to have an intervening isolating transformer.

You need to know how much current you motor will draw on start up as well as running because you will need to factor that in when you spec the associated components.

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Member

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#2
In reply to #1

Re: how do i get a 110/120v transfered to 140/150v?

06/25/2011 9:16 PM

Yeah, sorry about the two thread thing... I definitely underestimated this forum, which wont happen again considering I have gotten very fast and helpful responses on both threads.

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Guru

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#3

Re: how do i get a 110/120v transfered to 140/150v?

06/26/2011 12:10 AM

Since the AC voltage quite matches the motor DC rating, it will just work after simple full wave rectification, for motor the DC reservoir cap is not necessary.

Since current is small, you can use a series resistor to get the right amount of current if you need to make adjustment.

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Power-User

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#4

Re: how do i get a 110/120v transfered to 140/150v?

06/26/2011 10:29 PM

Make it easy on yourself and just purchase a dedicated DC motor controller. We specify the PWM drive from KB Electronics

http://www.kbelectronics.com/data_sheets/kbws.pdf

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#5

Re: how do i get a 110/120v transfered to 140/150v?

06/26/2011 10:40 PM

AC to DC full bridge rectification will result in

Where Vp = Peak of the AC sine wave, or the RMS voltage we refer to, divided by .707

So 120V from the wall socket = 120/.707 = 169.7V peak

2 x 1.697/3.1416 = 108VDCav

If you smooth it with a capacitor you regain a little bit, but you are still well short of 130VDC. So you either need to step it up to about 145VAC RMS with a transformer on the AC side, or use what's called a Voltage Doubler circuit on the DC side and then use a dropping resistor of the proper size to give you a 130VDC output. Since you are not really sure of the AC input voltage, I would use the voltage doubler and then use a trim pot (variable resistor) to adjust your final output voltage. Just make sure all the components you use can handle the motor current.

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