kfir katzin

[kfir katzin]

OK,great lesson!
iv watched the above mentioned lesson an have noticed at the bottom of the schematic there are 3 prongs inside a dashed line squar named A,B,C on top of each other and have also seen this in one ofyour other lessons the same dashed squar but with 5 prongs inside named A,B,C,D,E on top of each other,why are they enclosed inside that dashes? do they have any spacial function that they are markes off ? and most importantly,why do these prongs not apear in the timing chart?

[kfir katzin]

im just asking.since if i want to calculate the voltage drop across either load i first need to work out the current and in order to do that i need to find the the total resistence of the circuit and the resistance in this spcific case is of no use since one of the loads is a fan motor which has reactance rather than resistance.

[kfir katzin]

hi
on you last lesson video there are 2 loads in series one being the evaporator fan meaning that the current should and would be the same for both the def heater and the eveporator fan motor so if i put my ampmeter clamp to measure the current on different points in the circuit i would read the same amount of amps since its supposed to be equal at all points eventough one of them is non ohmic load m i right?
and in this kind of situation when i have 2 loads in series with one being a non ohmic load how can i work out my amps ?
secondly how can i calculate voltage drops across them in this case(since one of them is non homic and i cant employ equations that have R found in them)?

• This reply was modified 2 years, 1 month ago by kfir katzin.

[kfir katzin]

so if i want to work out the expected amps i should get in such a case(dealing with non-ohmic load) i would use
I=P/E 100/120=0.833A rather than E/R =I 120/15=8A or I=sqrtP/R=2.58A
AS THE CORRECT ONE TO USE IN THIS CASE IS I=P/E 100/120=0.833A without R in the equation
m i right?

• This reply was modified 2 years, 1 month ago by kfir katzin.

[kfir katzin]

alright!
thanks alot

[kfir katzin]

in the case of ASYNCHRONOUS motor CAPACITOR START CAPACITOR RUN does it use 2 capacitors one for the start one for the run OR one big capacitor which serves both functions start and run?

[kfir katzin]

the above mentioned ac ASYNCHRONOUS refers primarily to the CAPACITOR START INDUCTION RUN

[kfir katzin]

hi
i enjoyably watched your lesson about psc motor but one thing i didnt realy got is how the capacitor make one phaze shifted ? does the capacitor fulfill the same function on an ordinary run-of-the-mill AC ASYNCHRONOUS motor?does it do the same job?
secondly is ther any formula to work out by how many degrees the phaze is shifted by a capacitor? i know these formula 1/2×3.14xFxC has it got somthing to do with the shifted phaze?

[kfir katzin]

hi
another questions that came up are how does the vfd system change the direction of the rotation? does inverter board open and close the IGBT’S in reverse order than what you showed?
second i know what the term shorted mean when wires are involved,short to ground etc… but when you said a traic is shorted what exactly do you mean by that ? and why when a traic or diod is shorted they will constanly let current thruogh to the other side?

• This reply was modified 2 years, 1 month ago by kfir katzin.

[kfir katzin]

I SEE,
so if a washer is fitted with an AC asynchronous moter ,when its in the wash cycle it spins at a certian speed and after the drain it goes into spin cycle which is faster than wash in other words the motor will rotate much faster in spin cycle than wash,so how does the motor carry out faster rotation duering spin?how it can achieve different speeds without the inverter system? i know for example that the universal motor utilize a tacho fitted on the rear in order to count the speed by outputing small voltages (40v max).we’v experimented on this type of motor at my class.

[kfir katzin]

why are the shaded pole motor not efficient?what makes them inefficient compared to the PCS that use a capacitor? and how does this inefficiency affect or impair thier oparation?

[kfir katzin]

me again
how can i actualy measure the frequency of the inverter board? besides does it even nessecary to do that or a test of (pmw)VOLTS that the main pcb is sending will suffice in order to check if both the inverterboard and the main pcb is not out of kilter?

• This reply was modified 2 years, 1 month ago by kfir katzin.

[kfir katzin]

thanks i got it,
ok,so how is the speed of the AC asynchronous determined ?
secondly can you explain the differnce between DC BRUSH MOTOR AND AC BRUSHED MOTOR? if both usd carbon brushes do they work the same way?how do can i tell them apart? you didnt talk pretty much about the ac brushed motor

[kfir katzin]

splendid!
thanks alot

[kfir katzin]

me again
why is the system entiteld Variable Frequency Drive? has it something to do with the PWM signal being sent to the inverter in order for it to control motor’s speed? up to now i just cant figure out how frequency play a part in all this vfd system

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