how to measure all 3 phase voltages in 415v,50hz,3phase system?

[tamil004]

Hi everyone,

I need to measure all three phase voltages of 415v,50hz 3phase system to calculate over voltage(for example voltage above 415 bet two lines),under voltage (voltage below 390 ),phase reversal and phase loss. I familiar with working on PIC.I dont know how to start and to measure the 3 phase Ac voltages.if possible some one shares example circuit.if not how to start and what i am suppose to learn.thanks in advance

Regards,

Tamil

 

[paulfjujo]

hello,

You can use 3 smal transfo 240V/9V to acquire each phase. Transfo connected between phase and neutral ( primary volt = 415/racine(3)) and secondary low level like 9V eff.
Gratz bridge with 4 diodes ( or 2 diode with trafo with middle point 2x9V)
divider to ajust Umax to max ADC level input (5V peek).
and do acquisition sampling by timer at 10mS..
1 phase serve as synchro for the other...by adding a zero value detection (smith trigger) to detect phase rotation or missing phase.
some PIC have comparator detection with interrupt ...
With the ADC measure you can get the peak voltage of each phase at every time of 5mSec .(in the midle of arche of 10mS)

 

[tamil004]

I am looking for a design which uses resistive scalers from high voltage to ADC inputs ,instead of using transformer,can anyone guide me that like,what are the materials i should read to understand 3phase voltage measurement, phase loss, phase shift etc..,

Regards,

Tamil

 

[paulfjujo]

hello,


Resistive scaler is VERY DANGEROUS, because no galvanique insulation between POWER SUPPLY 415V and MCU system (and OPERATOR !)
it means, in this example, even Neutral is normaly near to Zero volt compare to the earth , it's true ONLY IN NORMAL SITUATION
if you have a probleme elsewhere in your 3 phases 415V installation, NEUTRAL can goes to HIGH LEVEL VOLTAGE.

Maybe you can use it , if all the MCU system is insulate from direct contact
and transmit the data to another system trought opto coupler. or by Radio frequency...
SAFETY FIRST !

Helwett packard has analog photocoupleur ..

You will be responsable if you are using this kind of interface.. OK only for the theory, but not a solution wich respect the Safety.

 

[tamil004]

hello,


Resistive scaler is VERY DANGEROUS, because no galvanique insulation between POWER SUPPLY 415V and MCU system (and OPERATOR !)
it means, in this example, even Neutral is normaly near to Zero volt compare to the earth , it's true ONLY IN NORMAL SITUATION
if you have a probleme elsewhere in your 3 phases 415V installation, NEUTRAL can goes to HIGH LEVEL VOLTAGE.

Maybe you can use it , if all the MCU system is insulate from direct contact
and transmit the data to another system trought opto coupler. or by Radio frequency...
SAFETY FIRST !

Helwett packard has analog photocoupleur ..

You will be responsable if you are using this kind of interface.. OK only for the theory, but not a solution wich respect the Safety.

Thanks for your reply.Is there any practical circuit,I have seen product , which directly takes only 3 phases and uses resistive scalers and op amp and microcontroler to achieve 3 phase voltage measurement, phase loss ,phase reversal measurment.