Use of signal generator for inverter

Brownout

Joined Jan 10, 2012
2,390
I never said there is any advantage to the method I described; I only said it would work with only a rectifier and transformer , which is correct. If the OP only has a sig gen and a center-tapped transformer and a handful of loose components (diodes, etc), there could be an advantage, depending on other circuit parameters.
 
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Hypatia's Protege

Joined Mar 1, 2015
3,197
@apurvmj

As I understand your posts you desire a 'balanced' drive? -- As other respondents have advised such is not necessary... Generally speaking, the center-tapped primary scheme is employed as a means of convenient implementation of a 'half bridge' (i.e. 'push-pull) driver. -- You may use it or ignore it -- The nature of 'mutual induction' will 'balance' the output (assuming a floating secondary and a symmetrical drive waveform, of course)...

I probably don't need to tell you this however I'm bound to say you'll need some amplification --- A typical function generator supplies up to a few tens of milliwatts and transformers are not active devices...

Best regards
HP:)
 

AnalogKid

Joined Aug 1, 2013
8,153
1. I would like to know the difference between signal fed to center tap transformer and by that of signal generator.
2. Coz with the signal generator you would not require center tap transformer. Am I right.
3. PWM method is fairly complex than signal generator for sine wave generator, so why isn't it a favorite method of generating sine wave?
1. For UPS designs, an output transformer with a center-tapped primary is fairly standard in low cost designs that make a "modified sine wave" output. This circuit uses two 60 Hz square waves rather than a sine wave. and the output is a stepped square wave that is a very coarse approximation of a sine wave. The advantage is that each end of the center-tapped primary is driven by a saturated transistor rather than a linear amplifier, which greatly reduces the heat produced, which greatly reduces cost. But that does not mean that a center-tapped primary is the best way to approach all UPS circuits. Also, note that the sinewave signal is not straight out of the signal generator. It must go through a power amplifier since it is driving the primary of a power transformer. Ever output watt must come from the sinewave power amplifier, a significant piece of design.

2. You are correct that with a single phase sine wave source signal you do not need a center tapped transformer primary. However, you do need a bipolar sinewave signal, such that the voltage at one end of the primary goes both above and below the voltage at the other end. This is the advantage of the center tapped primary - the driving signals at both ends of the primary can be unipolar (all above ground) without causing a steady state average DC value greater than zero, which would saturate the transformer core.

3. If you are saying that PWM is complex, so why isn't direct sinewave drive a favorite, then it is because direct sinewave drive requires a much larger transformer and removal of a significant amount of waste heat. PWM is a form of a switching power supply, with all of the size and efficiency benefits - at the expense of complexity. However, as noted above, producing a sinewave power signal of tens or hundreds of watts to drive a transformer primary is very difficult, especially when you consider the transformer turns ratio. If you are making a 120 V AC sinewave output from a 12 V SLA battery, the battery and primary-side power amplifier have to deliver *way* over 10 amps of current for every 1 amp at the UPS output.

ak
 
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