VFD error

[Jonathan]

Check the resistance between each of the UVW terminals and the DC bus, as if just one is short circuited you'll still measure a high resistance between the phase connections.

I wouldn't worry so much about the Chinese VFDs - how many recent threads have you seen where the VFD hasn't worked, due to the product not the user? Also adding a potentiometer to either isn't difficult, so I wouldn't make a decision based on that.

2.2 ohms sounds about right for the DC resistance.

Edit: Also, regarding whether to get vector controlled or not - with vector control you will get more torque from the motor (at mid-low speed) and better efficiency, but if you're currently happy with the torque from the motor then it's not really gaining anything so you might as well go for the cheaper option.

[routercnc]

Thank you Jonathan. Here are some pictures for reference:






Are the IGBTs the 3 pin components with a small heat sink? I was vaguely expecting 4 pins but am no expert.

To get to the DC bus I guess I need to get to one of the big capacitor pins? There are 2 boards stacked on top of each other with the top one looking like the high power side and the bottom one looking like the control/software side.

It looks like quite a job to take the top board off to get to the pins since they've soldered multiple pins in place around the edge of the boards to hold it in place (or prevent tampering !).

I'll have another look, but most likely going to send it away.

Found this article quite useful . . . .
The ABCs (and 1-2-3s) of variable frequency drives | Motors/Drives content from Machine Design

[Jonathan]

The IGBTs will either be 3-pin components (6 of them - like in the picture you linked to), or a single module containing all 6. Either way they'll attached to the main heatsink as they are the components that switch the power through the motor, so have the highest losses in the driver. I don't think you can see them in your images, as they're probably on the lower PCB.

Yes - the capacitors are connected to the DC bus so if you can get to both pins of a capacitor, that's the same thing. They seem to have missed out one capacitor on the top PCB (the big circle), so you can connect your meter to those pads. The capacitors say 400V on them, so they will all be in parallel.

The 3-pin component in the 2nd picture is some sort of MOSFET to make a switching power supply - it's probably connected to the yellow inductor to derive the logic supply from the DC-bus.