High voltage on the input is not something the drive can do anything about, the front end of a standard 6 pulse low voltage VFD is a passive system; it is connected, the rectification takes place with diodes, the rectified pulsating DC goes to the bus capacitors, no devices in there that can turn on or off by command, it just happens. So yes it can absolutely damage the drive front end and DC bus components. The only thing a drive can do when something “trips” is to turn off the output transistors so that nothing gets through to the motor.
The responsibility for protecting the drive from things coming in on the line side is YOURS. This is why line reactors are so important. A line reactor uses what’s called the “inductive tine constant” to slow down the rise time of any rapid change in voltage or current through it, which generally results in a lower peak as well.
But all that said, 490V is not high to a 480V rated drive. 515V is bad though, depending on how often that happens and for how long. So unless or until you get a recording voltmeter in there to check, you don’t know that is the cause of the damage.
But another thing that can damage front end components in VFDs is another important thing that a line reactor would do. It provides protection from “ringing” transients, meaning ones that have high peaks AND deep valleys right after them. The deep valleys can drop below the forward conduction threshold if the diodes, which means they stop conducting for a few cycles. That them means that diode does not contribute power to the DC bus caps. IF the drive is modulating (running the motor) at that moment, the load side transistors are pulling power FROM the capacitors, but with nothing coming in, they are depleted instantly and will want to recharge instantly. So when the ringing transient is over, the capacitors will try to pull current from the line AT THE AVAILABLE FAULT CURRENT RATE for that brief moment. So for example if the AFC is let’s say just 10kA ahead of that drive, then that ringing transient takes place while your motor is running and 2 of your diodes fail to feed the DC bus because of it, the next diode in the sequence has to make up the lost energy sucked out of the caps by the motor, so it briefly pulls 10,000 amps of current for a fraction of one cycle! They can often survive that once in a great while with plenty of time to cool off, but multiple hits in succession with take them out.
I’m not saying this was definitely the problem, there are other possibilities, but I’m a big advocate for line reactors as “cheap insurance” for expensive drives.
One of the other things that can damage the front end of VFDs is the use of line side starters that open and close ahead of the drives every time you use them. Because of the issue stated above about capacitors pulling AFC to charge themselves, all drives use what’s called a “pre-charge circuit” that limits the current that flows into the capacitors. In small drives that is usually a current limiting resistor that is in the circuit for just a second or so when first powered up, then it is bypassed with a relay. Those resistors are generally designed to last a few thousand operations, which can be a long time if a drive is powered down and back up maybe once per month or even per week or day. But if there is a line side starter ahead of the drive that closes every time you want to run, that will stress that pre-charge resistor and burn it out, then the other components fail in short order. Again, just spitballing here but making you aware that there are many possibilities beyond the 490V issue.
