Delta Inverter Repair
It isn't always just about fixing a fault, it's taking the time and effort to work with a customer to ensure the item goes back to site and works for a long time to come.
Take this Delta Electronics inverter, its nothing out the ordinary. A decent 11kW variable speed drive, well made and reliable. Have a look inside it - it has quality Nichicon branded capacitors, the boards are conformally coated and the power interconnections are all quality metal components. The more eagle eyed amongst you may see something which isn't quite right, and you would be correct in noticing an area of the board is extremely burnt.
The customer rang me this morning, a little perplexed as this drive was brand new off the shelf and upon fitting it blew instantaneously, belching out smoke into the panel. Obviously this isn't what should happen, and the first thing we think is its either defective from new, or there is an external issue. My money is usually on an external issue as these inverters have a great reputation for reliability.
Upon discussing this issue, we took a trip to site to have a look at the damaged inverter and also the panel. As soon as the door was opened I knew exactly what had happened. Connected to this inverter is a DC bus brake chopper unit. I couldn't be sure until I got my multimeter out but I could have bet my bottom dollar the resistance across the DC supply leads being low. It was. The chopper had gone short circuit resulting in the 36 ohm braking resistors permanently being connected across the DC bus. This meant that when the drive was powered on there was a massive stress on all the input circuitry which never disappeared, and sooner or later something has to give.
The inverter is back with us now for repair, and the braking module will be following. It took a little time out of my day to do this but the end result paid dividends and saved another new drive failing instantly on power up. It would have been easy enough to take the drive away, fix it and just ship it back but that isn't what we are about. In a few days this drive will be repaired and back on site, with 100% confidence it will work as expected.
