DC 2 AC inverter with synus output in UPS systems

Hi all

How exactly synus output voltage is generated in UPS systems ? I understand how rectangular or PCM voltage is generated but in case when pure synus voltage is needed , how this is done ?

Thanks Elico

Reply to
RealInfo
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synus voltage is needed , how this is done ?

Cheap designs use a transformer. The output side (appliance side) will have the line voltage on it, passing through the output side as it goes to the receptacles. As this is taking place, the other side of the transformer (low side) is generating a low voltage, a voltage that matches your battery. THe battery is connected to the center tap of the low side (+) and will be a push pull type of inverter.

When commercial power is present on the high side of the transformer it will also be present on the low side. This voltage should match the battery voltage or actually be a little higher. Because when it is a little higher it is also used to charge the battery! Of course there is some more intelligence behind it to control the charge rate. This also may explain why some UPS systems will not charge a battery that is to low, because the active circuit is not operating due to insufficient battery voltage.

When line voltage goes away or even dips in the middle of a wave the low side will see an absence of voltage or I should say the unloaded inverter will now detect a load present to it's inverter transistors and thus create current in the primary at that moment.

Just think of an inverter operating at all times into a push pull primary (low side) but the secondary has voltage is back feeding it. The primary side will not generate any current because it is being canceled out however, when the back feed takes a lunch break at any time on the sine wave, there will be no canceling of currents and thus at that point, the inverter will contribute current to the needed high side voltage.

That is the best I can explain it.

You can do this with high frequency toroidal transformers too, the difference being you need to monitor the line voltage directly from your low side inverter circuit to know when and at what phase angle to come in on.

Jamie

Reply to
Jamie

synus voltage is needed , how this is done ?

Most use PWM, like a class D audio amplifier.

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John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
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Reply to
John Larkin

synus voltage is needed , how this is done ?

Thanks Elico

Reply to
RealInfo

when pure synus voltage is needed , how this is done ?

Simple answer, pwm and huge inductors to smooth it out. Big bux. Lesser approximations vary considerably.

?-)

Reply to
josephkk

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