Weird stuff happened when I plugged in a new inverter.

[Inferno]

I almost posted this in the CNC forum.

Long story short, I'm building a CNC machine.
I'm putting together the structure some days, working on electric/electronic components other days and then working on other stuff other days and so on.

I bought a Chinese inverter. Model #VL620-A. I bought a 110V model for the 2.2KW spindle. It was all part of a package.
I looked at the book but I'm too freakin old to read 3 point type. I ended up looking at a couple youtube videos.
They all showed the wiring the same way. Neutral to the far left. Earth ground to the far right. Second from the left is line voltage.

I took a computer cord and stripped off the end and cleared the insulation on the three wires. I soldered connectors to the wire and then insulated them with shrink tube.

Green is obviously earth ground.
White is usually common/neutral
Black is traditionally line

That's how I hooked everything up.

This is where stuff got weird.

I plugged it in in my living room. It POPPED. Then my TV and all my other components went off. But the inverter stayed on, with the display blinking in an error state. I didn't think to check the error.
The weird thing is that the breaker for my TV popped but the outlet I plugged the inverter into was still live.

This shouldn't be possible, I don't think.
Is it possible I have the inverter wired backwards and I, somehow, fed enough voltage back through the neutral to overload the TV breaker?

I do plan on using a continuity tester to make sure the power cord white is, indeed, the neutral. If the black and white are swapped in there then that would probably cause issues.

I also detected magic smoke from the pop. I sniffed inside the inverter and it doesn't smell like magic smoke. I can't imagine I did any damage inside it.

Any ideas?

 

[JimDawson]

I think we're going to need a picture of the way you wired it. That ain't normal.

2.2 KW (3HP) is a lot to be running on a 120V circuit, full load current on that is going to be in the range of 30 some amps.

 

[Inferno]

I had my cat hold the unit so I could take pictures.

 

[JimDawson]

I think the ground is the screw below where you have it connected. Looks like you have the ground connected to the brake - terminal.

 

[Inferno]

I think the ground is is the screw below where you have it connected. Looks like you have the ground connected to the brake - terminal.

Ah, I can see that now. Frain Bart.

Thanks.

 

[JimDawson]

And I have a question. How did you get your cat to hold still long enough to take that picture?

 

[Inferno]

And I have a question. How did you get your cat to hold still long enough to take that picture?

When she sleeps, she REALLY sleeps. That's when I trim her claws.

 

[mksj]

As Jim indicated, you have connected the braking terminal to the ground wire, but most likely you popped the breaker due to the high current draw when charging up the capacitors. VFDs will stay on for around 5 minutes after the power is turned off due to the charged capacitors. If there is a lot of momentum in the system when power loss occurs, the VFD will use the regenerative power to keep everything running until everything stops. The display is the last to shut down because it takes very little power.

If the output is 240VAC 20A 3 phase the input converting to single phase at 120VAC would be 20Ax1.73x2 or around 70A. A 2.2 kW motor is 3 Hp, so around 38A at 120 VAC and that is with conservative overload parameters, the typical breaker would be sized at 125%. There are other factors such as using a DC choke which will tame the current pulses, but there is no provision for that on this VFD. Minimum breaker size at 240VAC for a 3 Hp VFD is typically 30A. Not really practical to use 120VAC.

Fortunately my cat purrs when she gets her claws cut.

 

[Inferno]

Interesting. So, e en with no spindle connected it will draw that much power?
When it's all said and done, I can give it a dedicated circuit. Or I could get a different inverter when I'm ready to start making things.

 

[macardoso]

So you ended up connecting your ground wire to the braking resistor to the "-" end of the braking resistor which is most likely directly connected to the lower rail of the DC bus. Effectively you shorted your AC line (hot) to ground through the diode front end of the drive.

If you had a GFCI outlet, it likely would have tripped before the main breaker blew when it detected a spike in fault current through the ground wire.

It will *probably* be OK, but I'd be worried about damage to the AC->DC converter (diode front end) inside the drive with a dead short through the rectifier.

I really don't want to come across as demeaning so please don't take my comments as such. I work in the automation industry and want to see everyone be safe when working with power. I would encourage you to slow down, read the manual, and ask questions when you are unsure. This is a small VFD but it still carries 180VDC on the bus and holds that in capacitors. You could really hurt yourself from a shock if exposed to that. Likewise, you are hooking up a lot of power there and that cable does not look like wire rated to carry 30A. You'd want 10 gauge wire or larger for that power cord or you could risk a fire.

You guys are very lucky. Wife and I have 3 cats and have to wrap them in blankets to have any chance at trimming their nails. Usually ends up with 3 very ticked off kitties by the end of the night!