Question about a rectifier PCB of a welding power supply

Thread Starter

BlackMelon

Joined Mar 19, 2015
85
Schematic_asked.jpg

Hello,

I am converting the aforementioned PCB into a circuit. The relays are marked "RL" and highlighted by corresponding colors: yellow for the contacts and coil of the relay 2, for example. Connectors are represented by open circuits. However, I don't understand how the circuit circled by the red circle works.
To my sense, it is a transient protection system, since it got TVS diodes (KE150CA). However, why do we need D5, since it will make the whole protection system work in only one direction? Also, I don't get the idea of using C5 here too.

Should you provide resources for my further studying, I would be appreciated.

Sincerely,
BlackMelon
 
Last edited:

AlbertHall

Joined Jun 4, 2014
9,875
There is a contact labelled RL2 but coloured green up near the inductor. Should this be RL4?

What is COM3 connected to?

Maybe they are using the KE150's as 150V zeners, and then together with R4 and C5 may give a delayed turn of RL2
 

Thread Starter

BlackMelon

Joined Mar 19, 2015
85
There is a contact labelled RL2 but coloured green up near the inductor. Should this be RL4?
Do you mean the green contact that is connected to a NTC47-D15 thermistor? If so, that one is RL1. Sorry for my handwriting.

What is COM3 connected to?
It is wired to a switching board, containing power MOSFETs and also control electronics. I will provide you more detail after I finished drawing the schematic of that board.

Thank you for your advice. If I have any updates, I will let you know here.

Sincerely,
 
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