regenerative ac drive

Hi I'm certainly no expert on thyristors, but are they not supposed to continue to conduct for as long as they are forward biased . Would a diode not work this out ? Please educate me.

Best regards

Joe

Hello DHARMARAJEN

If you supply further information, with it may be possible to assist you.

Kind Regards....

motor with different power and speed

hi dharmarajen, SCR blown in AC to DC rectification ? then what is current rating of SCR? and current required at AC side? give me more details.

PLEASE IGNOR THE PREVIOUS ELEC DRAWING. HERE IS THE ACTUAL INVERYER CONFIGURATION. LET SAY THAT: WHEN USING DRIVE 2 , THE THYRISTOR ON RECTIFICATION UNIT BLOWN. WHY?.PLEASE ADVICE. THANKS. DS.

Dharmarajen,

SCR blow may have following reason

1. current drawn in 2 inverter may be > than SCR current.

2. this happens only 2 inverter along running?,then check 2 inverter output current.

3. if step 2 is problem, you can verify inverter by connecting 2 motor to inverter 1 or 3.

4. if this happens all 3 inverter running together?, then you consider SCR current to total 3 inverter output current.

Check these and Let me to know result.

moorthi.

what happen if one motor out of 8 on inverter 2 is short circuited due to water in motor.

Hello DHARMARAJEN

Fault analysis is so much easier, when even the basic schematic is supplied.

Are the Inverter Units the same electrical size? Do you have a spare Inverter?

If so, change over or try a spare, in temporary replacement of Inverter2 - remember to temporarily alter the control circuits too.

If the SCR at Rectifier unit still blows with Inverter2 replacement connected, then problem is not the Inverter2, but further along load connections.

<"what happen if one motor out of 8 on inverter 2 is short circuited due to water in motor.">

You will normally get overload situation on Inverter2, and probably on Rectifier unit also.

This may be the cause of your problems.

The other possibility with the Rectifier SCR blowing, is that it may be incorrect type or faulty - I have found brand-new semiconductors as faulty before they were installed.

It may be that either/or the current/Voltage of the SCR is insufficient, thus causing failure, but one would normally expect to see a circuit breaker or fuse open circuit before failure of the SCR.

When you have finally located and fixed the trouble, go around your installation with a clip-on digital ammeter, with a peak-and-hold system, take notes of all readings, both running/peak, while your installation is running, and make a record of same.

Then, next time there is trouble, it is much easier to locate faults.

I decided to do this years ago, when brand-new equipment was connected and being commissioned.

Sure it took a bit of extra time, but when faults occurred later, it was much simpler to locate the fault/s.

Advise your progress here, thanks.

Kind Regards....

Please ignor the previous drawing. this is the as build elec drawing.all drive are of differrent powers, but problem occurs when using a lower power drive. thyristor on rectification unit blown several time. Please advise, Thks: Ds

I will suggest to check the characteristic of Drive and its starting current if matching with thysistor characteristics. Check if motor stalls.