Hi Guys,
I had a spare half hour this morning, so I did a drawing of the connections between a VFD and the motor.
I am not familiar with wiring standards in the UK. However, there are some differences between what you show and what is likely to be found here in Canada.
NOTE: I have made no attempt to explain how to wire external controls, these will be dependent on the manufacturer of the VFD you choose.
View attachment 69930
In the UK "N" would be the mains neutral, whilst "L" would be the live supply wire. In the USA and Canada I believe that the supply is a centre tapped 220 volts. The 220 volts should be wired to "L & N"
The other gotcha is both VFD's and 3 phase motors can be had in 220 volt and 440 volt ratings. Using the wrong one risks motor damage and possibly VFD as well.
In Canada, you can find 3phase wire that is Black/Red/Yellow like you describe. But it is more likely to be Black/Black/Black with a Green Ground. Other combinations are also common.
The important things are that the cable be:
1. the right gauge which depends on the cable length and HP of the motor,
2. be rated for 3ph operation at the required voltage and current,
3. that all motor connection wiring be flexible stranded cable not solid wire,
4. If necessary, it might also need to be shielded to reduce noise from the VFD which can damage other equipment.
High quality VFD Rated Cable is available from Mouser and Digi-Key. Digi-Key staff are VERY helpful and knowledgeable.
Unshielded stranded 3ph wire is also a available at places like Home Despot.
Your ground wiring drawing shows the mains ground connected to the motor ground. This is not a good idea. They should both be connected to the respective input and output grounds on the VFD. Other connection paths can create ground loops. With grounds, you want all ground currents to share a common path and not have choices between paths. Basically, ground current can generate voltage and these relative voltages can play havoc on adjacent circuits. It's best practice not to have them.
If the motor cable is shielded, the shielding (mesh/foil/ or both) should be connected to one location at one end but not both ends. I prefer to connect it at the VFD end because the VFD creates way more electrical noise than the motor does. This shielding is intended to prevent the power wires from acting like radio antennas inside your shop and affecting things like DROs, Bluetooth, Computers, Calculators, 3D Printers, phones, radios, etc.. When I measured the noise on my Mill VFD, I was mortified by how bad it was. Shielded cable clobbered that problem.
Mains side noise is also commonly encountered with VFDs. Sometimes you need to install mains side filters to prevent this noise from feeding back into your shop or home wiring. Digi-Key sells nice filters for this, or you can make your own with some iron cores.
VFD's work by rectifying the incoming AC voltage and usually providing a doubled DC voltage, ie 220 in 440 out.
I'd leave this DC 220/440 stuff out of your writeup. It will be what it will be and users don't need to know what it is because they might confuse it with different 3 phase voltage systems. Just stick with overall VFD input and output. Ie 220 single phase in, and 220 three phase out. If you feel you need to add the DC part just use it to say that is how they convert single phase to 3 phase as per your next piece as follows.
This DC voltage is then chopped at a frequency that sets the motor speed. High frequencies greater than 50/60 Hz will cause the motor to turn faster. Conversely a lower frequency will cause the motor to turn more slowly. Often you will find VFD rated motors that incorporate a fan driven by an independent motor, this is simply because as the motor is set to run more slowly less air can be blown through the motor by the internal fan.
And add that non-vfd rated motors may need extra cooling or conversely don't run them below 45 rpm or so.
If you want, you can repost your writeup and I'll delete the original and my comments.
I think it's a good idea to provide something like this. It's all covered elsewhere in the forum but I like it all in one place.
Another option would be to get a VFD Wizzard like
@BaitMaster or another forum VFD guru to do a write up for us. Those guys do this stuff for a living and are 100% familiar with the Canadian Setting. He might also be familiar enough with all the different VFDs out there to make a generic setup guide for the controls too. Alternatively, you or I could do it based on our models - I have both Brand Name Tecos and Generic Chinese VFDs.
