Triacs for low current loads

Thread Starter

Justus22

Joined Dec 8, 2018
12
Hello,

I want to build a circuit with triac's to control power contactors and valves. For the power supply I want to use a simple capacitive power supply.
Because of the low current load I can't take advantage of only triggering the triacs during current crossing. Therefore I would have to drive the gate permanelty with about 10-20 mA. But thats too much for a multiple triacs with a simple capacitive power supply. The holding current for standard triacs from ST for exmaple (ACS AC Switch) is abount the same as the load itself especiall for driving the power contactors. I looked at phototriacs, these have much lower holding currents but I don't need any isolation and I rather drive the triac directly. What is the best way to solve this.

[Valves]
Power supply 230V/50Hz
Inrush 24 VA
Hold 17 VA

[Power Contactors]
Power supply 230V/50Hz
Inrush 24 VA
Hold 3,4 VA

Best regards
 

MaxHeadRoom

Joined Jul 18, 2013
28,829
How is this going to supply solenoids and contactors, these appear to be AC versions and if not supplied with the correct current can fail, or see partial movement of the armature.
It is far more efficient to use DC versions, with less chance of premature failure seen in AC types,.
What is the application?
Max.
 

Wolframore

Joined Jan 21, 2019
2,610
That looks one part scary and one part inefficient and you plan to drive solenoids??? Even if it was well designed you're looking at about 10% efficiency. Plus that's just scary looking. So if you want to dim you lights and burn stuff out... maybe.
 

Thread Starter

Justus22

Joined Dec 8, 2018
12
How is this going to supply solenoids and contactors, these appear to be AC versions and if not supplied with the correct current can fail, or see partial movement of the armature.
It is far more efficient to use DC versions, with less chance of premature failure seen in AC types,.
What is the application?
Max.
Part of it is to control a star delta switch, the rest is for controlling valves depending on some input signals. (The star delta switch is looked against each other. That way it is impossible to switch both contactors at the same time even in the event of a failure) At the moment we are using a circuit that only uses power contactors, delay switches and pressure switches. All is AC based and works fine without any failure for a long time. But all the wiring and the delay switches and extra build blocks are quite expensive. In addition it makes the wiring very complicated.
I want a simpler and cheaper microcontroller based solution. I thought about a DC version but thats more complicated with more parts.

That looks one part scary and one part inefficient and you plan to drive solenoids??? Even if it was well designed you're looking at about 10% efficiency. Plus that's just scary looking. So if you want to dim you lights and burn stuff out... maybe.
The triac is driving the solenoid which uses the AC supply. The power supply is only for the microcontroller and the gate drive
 
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