Simulation of AC Voltage regulator

A

anso-engineer

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Hello, can you have a look what wrong with my simulation based on this scheme:


It processed too slow, please find simulation files attached:
 

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  • Voltage Regulator demo.zip
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For info, that is not a "voltage regulator", it's a phase control light dimmer type circuit.

The triac firing is delayed from the start of each AC half cycle, with the delay depending on the pot setting. They are great for filament lamps, but not much else.

Some things can be damaged by the sudden high voltage part way through each cycle causing excess current surges.

Waveforms at different "dimming" settings, brightness decreasing:

 
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ps. If you are looking for a motor speed controller, a thyristor based one can be quite effective, if an appropriate circuit is used.

The links below are examples - an absolute minimal, crude version and a slightly more sophisticated one.

Again, these are not voltage regulators; they work from the motor back EMF, which is proportional to its speed. They only work with "universal" (brushed AC) motors as in typical AC power tools etc.

The thyristor must be a "sensitive gate" type.

Adjustable Drill Machine Speed Controller Circuit - Homemade Circuit Projects

The proposed variable drill speed controller circuit maintains a constant (adjustable) speed over the drill machine motor, regardless of the load.
www.homemade-circuits.com

 
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Great, I already found a already prepared for LT Spice schematic and try it. Also there was an issue with Diac library, I found a solution.
Here how it looks like:

I would say that values in Yellow circles not much applied for results, so I minimized it.
 
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For finer control of dimming and less hysteresis but there are stronger 10k~20k pulses (noise) which is better for unity power factor loads but then for Tungsten bulbs without the 2nd RC filter is better but has 50% hysteresis after which you can dim down to 5%. This is due to current gain in the triacs BJT's reflecting the load back onto Diac RC discharge and reduces the Tau = RC time constant when the bulb is conducting at much lower cool resistance.

Show below is the load voltage drop and cap voltage below that from 230Vrms.

 
Last edited:
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Yeah, your example looks good, I should additioanlly consider about some details.
Btw, when I inspect most of this circuits variation, I have found that acros DIAC is voltage drop form 32 to 14 V.

From Where this 14V comes from?

My closest assumtion is that according datasheet it related to the delta V, and it's minium 5V (in mhy case it's32 - 14,3).
 
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I notice that your AC voltage source is set to 220 Volts. Be aware that the voltage setting for a sine wave in LTspice is for the peak voltage.

If you want your simulation to run at the RMS voltage, you need to multiply the desired RMS value by 1.414.
 
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