help identify some components

this is a mains powered ZVS flyback driver.

https://ct4s.de/img/uploads/384306.png

i have a few questions about this schematic. if you look at the attached pic i have some colored circles.

1. on the left what is the part labled "3kwp"?
2. on the right, what is U2?
3. im assuming all the "green" downward pointing arrows get connected together.
4. the pink circle says "connect with U2. what part of U2??

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https://www.youtube.com/user/lokeycmos?feature=mhee

1. This appears to be a PTC resistor, as initially bridge gets voltage thro this and after a while wnen the charging current passes, the ptc gets HOT and increases it value to help reduce inruhs current. meantime the relay operates and tabyepaases the PTC. It is capable of withstanding 3KW for a very short while.

2. U2 is an aux power supply and it is 15V DC as mentioned there. This drives the circuit.

3. YES. all of them are -ve return of the rectified DC of mains supply. (NOT to be grounded and even DON'T TOUCH)

4. same U2 power supply is to be extended to the element on the left also. On right side he connected and left side he showed indication instead of showing a wire.

But beware, as it is NOT sufficient that you know what is shock. the other citizens across globe, espcoially children enthusiastic buit ignorant would suffer fatal shocks. I suppose that such circuits should have the mandatory symbols of skull and bones and a warning .

All the best.

thank you for the reply! could you elaborate some more on how the PTC and relay work and what they do? thank you

as power is applied , if we dont use the pTC as series element in mains input , the in-rush current to charge the 3300uF capacitor would be rather high. this might blow the protection fuse.or the diode elements of the bridge. Once we use the PTC resistor, as current starts flowing its value increases with the heat generated.thus the charging would be little slower .
once the a voltage level is reached sufficient to operate the coil of the relay, the relay operates and it would bye pass the PTC element with it's contacy shorting the said PTC.

i order all my parts from digikey.com. ive never had to order that type of resistor. could you possibly point me in the right direction on digikey.com? thanks much!