# Understanding monophased rectifier

Discussion in 'Homework Help' started by activee, Jun 4, 2014.

1. ### activee Thread Starter Member

Jan 16, 2014
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0
I've a problem understanding this monophased rectifier (I'm not sure it's called a rectifier in english).

It says Vab = Vam - Vbm. I don't get why it's not Vab = Vam + Vbm and the arrow Vbm should be going upward instead of downward.
And also why Vam = E.sin.(ωt)?

I can translate the text if needed but I guessed the picture was self-explanatory.

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Feb 17, 2009
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3. ### vk6zgo Active Member

Jul 21, 2012
677
85
The two voltages Vam & Vbm at any given time are opposite polarity as referred to "M" which is the centre tap.
Hence one voltage is given a negative sign.(this is completely arbitrary,they could have chosen either one)

If you subtract a minus,you end up with a positive,so the amplitude of Vab turns out to be exactly what you would expect.(Vam+Vbm)

They need to emphasise the different signs of Vam & Vbm to help explain how a Fullwave rectifier using a centre-tapped transformer works.