Posted 18 June 2007 - 10:17 AM
Posted 18 June 2007 - 11:34 PM
P.S. the voltage on the bus will be DEADLY so be careful!!!
Posted 19 June 2007 - 03:41 PM
I had a similar problem on a 15Kw Mitsubishi drive you’re talking over
13 years ago. The drive was tripping out on under voltage, all measured voltages
appeared to be in acceptable limits….it would just trip out but nobody ever saw it trip out.
All you would see was the red led on. Anyway it transpired that it was a genuine under voltage error the drive would trip out in the early hours of the morning, as the world was awakening and draining the grid system.
Posted 19 June 2007 - 06:38 PM
Usually, there is a resistor in series with the bus capacitors that limits the charging current when the drive is powered up. This resistor is then shorted once the capacitors are fully charged.
Typically, the shorting is done by a relay. If the soft charge resistor does not get shorted due to a fulty relay or similar, then it will come up with under voltage trips as soon as current is drawn.
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Posted 20 June 2007 - 02:34 PM
Now i have the same problem with another inverter with Sanken type, it is 10 hp 380V. it has undervoltage fault too.
For the first time, the inverter is working well, then it seems do a restart. then i checked the fault history, and said undervoltage. I have checked the line power it's ok. I have checked the rectifier, it's OK too.
I have checked the power capacitor after the rectifier. it seem drop in capacitance. It has 4 capacitor which was written 820 uF/400V. And the capacitor arrangement is 2 capacitor in paralel and then series with 2 paralel capacitor again. So from I know it will have equivalent capacitance 820 uF but has a rating voltage for 800 V. when I measured this capacitor with capacitance meter, mit has only about 700-720 uF. So the real total capacitance will be dropped to 700 uF. Did "120 uF" lost can make this inverter undervoltage?.
I have searched for the sense circuit for the undervoltage sensing, and i found nothing for this. but i have this in the circuit for power supply. So my opinion is the circuit know that undervoltage failure from its supply voltage (control supply about 5 and 24 V ) CMIIW...
And control supply is influenced by the switching PWM and the power supply from main capacitor.From my problem above, if I change the capacitor so it have its capacitance back to 820 uF again or I make it bigger, it will make my inverter being good. can anybody give some advice?
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