# thanhdd

Member Since 19 Aug 2007
Offline Last Active Feb 09 2009 04:20 PM

### In Topic: Check Short Or Open Circuit Using Pic. Help Me!

09 February 2009 - 02:24 PM

QUOTE (marke @ Jan 29 2009, 07:23 PM) <{POST_SNAPBACK}>
Hello thanhdd

To determine whether there is an open circuit (high impedance) or short circuit (low impedance) between two terminals, you apply current and measure the voltage across the terminals, or you apply voltage and measure the current.
You need to do this with or without a pic micro. The measurement of the voltage and/or current is done using analog circuits with the output either an analog value that you put into the A/D input on the PIC, or a digital voltage (0 or 1) from a comparator that you put into a digital input on the pic.

Best regards,
Mark

You helped me more knowledge.

The reason I want to use microcontroller is I think it's like pro... I think so? Is it right?

Use PIC, I can practice and improve my skill. I want to check open and short circuit a same time also.

Pls give me more advise about PIC, about digital voltage with comparator... if you have free time.

### In Topic: Magnetizing Losses By Star-dyn Connect In Dfig

01 May 2008 - 07:09 PM

QUOTE (thanhdd @ May 1 2008, 07:18 PM) <{POST_SNAPBACK}>
In Induction Generator Double Fed(DFIG), stator connect Dyn when wind speed (speed of prime mover) is high; stator connect Star when wind speed (speed of prime mover) is low. This reduce flux level and magnetizing losses. Why?

When wind speed low, P1 low, stator connect Star so that U1 low, so keep I1 = const, flux is const
(If stator connect Dyn, U1 will high but I1 low, flux is low too and not enough to magnetize iron)

When wind speed high, P1 high, stator connect Dyn so that U1 high, so keep I1 = const, flux is const (If stator connect Star, U1 low but I1 will high, flux will very high, machine will too hot and magnetizing losses will increase)

Is it wrong if I think so?

### In Topic: How Does Dfig Operate? How Does It Start? Help Me

02 March 2008 - 05:46 PM

QUOTE (thanhdd @ Mar 2 2008, 03:33 AM) <{POST_SNAPBACK}>
I don't understand the operated principle of DFIG (induction generator double-fed). Can anyone help me understand : "when DFIG starts, where does DFIG receive electric energy from? (from grid(stator) or from converter)" because when DFIG starts, stator directly connected to grid, rotor also connected to grid via converter while speed below synchronous.
Help me!

Using residual magnetism of rotor like ordinary induction generator ????