I bought the cheapest VFD on Amazon for my 3 phase drill press 

Hi Bob. I'll pin this comment so that others will see it and can appreciate your concerns. Your recommendation to fit everything in an earthed box is the ideal solution, however I disagree that the wiring is not safe. It could be safer, but there is nothing at mains potential that can be touched. The mains input goes via a strain relief grommet into the switch box, which is earthed, the machine, motor and the VFD are all earthed. The VFD is located at the back of the machine, well away from swarf or anything you are likely to touch while the machine is powered. The E-stop isolates everything from the mains input. The only thing that could occur is if a wire came loose from the screw terminals, yes there is the possibility of a live wire, but the whole shed is on an RCD. I am personally comfortable with the level of safety. This approach to VFD installation is very common. Every installation is different, and anyone installing such equipment should consult someone qualified if in any doubt, this is written on pretty much every piece of electrical paraphernalia that I have come across, so I didn't feel the need to repeat this advice. FYI, it is not possible to edit a RU-vid video once posted.

Thanks!

Good point, sounds plausible.

Hi Paul, will do. Thanks for stopping by.

Thanks. I hope it makes some sense. There are a huge number of features to configure if you want to on these things, but you can get away with just a few basic ones. There's probably loads of optimisations to be done but it works so I'm not going to fiddle with it unless I have a reason to.

Hi, thanks for your question. I have set the minimum frequency on the VFD at 15Hz as below that the motor torque drops off like a stone. The motor is 1425rpm at 50Hz, so at 15Hz that's about 400rpm. I don't know how other motors will respond, some may be better. Hope this answers your question.

A good quality 0.75kw VFD should have no issues with a 0.75kW motor, but if you are getting a cheapo Chinese one like me, it's probably worth spending the little extra on the 1.5kW version, then it may well last longer as it will be less stressed. Hope that helps.

@@ollysworkshopThanks. Yes getting an Ali Express special. Difference in price between 0.75 and 1.5 kW is tiny. Will go with the 1.5 so.

Hi. Glad you found it useful. The inverter remembers all the settings after losing power. My system is run through an e-stop switch. When I hit the e-stop all power is disconnected. I can confirm that it's been working perfectly since installation.

@@ollysworkshop Thank you for the help Olly! Another question that popped up. I have a 0.75kw / 3.2A motor. Will a VFD rated for 2.2kw and 12A blow the whole thing up, or does that mean it is rated ''up to'' those numbers?

It is rated up to those numbers as you suspected. What you do when you set the thing up is set the max volts/amps/watts for the motor so that the inverter does not blow the motor.

​@@ollysworkshop Thanks Olly, really appreciate you taking the time to answer. I've been stuck on these questions for a couple of days, but now im feeling confident enough to get a VFD and start the conversion. Wishing you a ton more of subscribers! Best regards from Sweden

No problem. Best of luck with the conversion. Feel free to ask if you need any further help.

Hi, great question. I'm assuming that the VFD is also rated at 1.5KW, so in theory should be fine to drive your motor - although chinese KW are sometimes a little more generous than regular KW. I can think of 4 things .... 1. Loose/bad connection - always the first thing to check 2. Could be a dirty potentiometer - clean with contact cleaner or WD40, or replace 3. Double check all the settings - there were several setting on mine that related to how the pot affected the VFD. 4. Electrical noise pickup on the wires to the pot - if wires are too close to motor, motor wires or mains input, it could cause interference. Separate if you can, also try screened wire, either to the pot or the motor - connect the screen to the GND connection at the VFD only, this avoids a ground loop which could make it worse. The noise would most likely be coming from the motor wires, and it's best to suppress noise at source, rather than try and protect other things. Hope this helps, let me know how you get on. olly

@@ollysworkshop thank you for these helpfull tips, the connection ports are still a mistery to me. No matter how hard i turn the screw on the connection ports the cables are still very loose. So i attached the wires end to pins and pushed it through the green connection ports on the vfd, i know its not the proper way but i have absolutely no idea how to mount them hahah

The little green connectors are called cage clamps. There's a little moving metal cage attached to the screw. They usually come done up. When you loosen the screw, the cage descends and reveals the hole where you poke the wire. Do it back up again to clamp it. I agree they can be a bit confusing compared to normal screw clamp style terminals.

@Debra Jones, Hi. Thanks for the question. I haven't tried that, but will take a look and report back.

@Debra Jones, on my inverter it looks like there's 3 ways to do it. 1. Use the programming menu to change the parameter 2. Set up the 'm-fun' (multi function) key to be forward/reverse. 3. Configure one of the digital inputs to do the direction change with a switch. Of course your inverter may differ in the details, but should be generally the same. Feel free to ask if you need further assistance. Thanks

Just got reverse set up using the "m fun: key. Many thanks for your help

@@debrajones5099 no probs. Hope to see you again.

Hi Michel. That's a great question, I've just measured it at ~260V, so doesn't look like it's giving it the full 380V. This may be that the unit can't boost the voltage or I've not set it up quite right. I'll have another look later and see if there's anything about it in the manual, and confirm which it is. Thanks

@@ollysworkshop ​ OK, that figures. Looks like it's a 220V unit, the 260V you're measuring will be from the motor acting as generator and artificially pushing the voltage back up. Running a 380v motor on 220v is usually OK (although under heavy load you may end up overloading the windings) but will result in a loss of power (by a factor of sqrt(3), which takes your motor from 380W to about 200W). Solutions to this (i.e. getting moar powah) would be: - Get a 220v to 380v VFD, but that's gonna set you back quite a lot more than 20 quid - Laying your hands on a 220/380 rather than 380/440 motor, probably the cheapest option, especially in those sizes, check your scrap yard for A/C or ventilation fan motors - If you can find one, a 3 phase 220 to 380v transformer (again, scrap yard if you're very lucky). - Single phase motor, more expensive and you lose the benefits of the VFD. - Fix up your homebrew VFD to put out 380V (if it didn't already), maybe? Anything that includes replacing the motor might also benefit from going to a bigger motor as well. 3/4 or 1hp is a very worthwhile upgrade for a drill press. This is the same area of pain I have with my mill. My lathe and grinder are fed by a 4hp rotary converter generating 220v 3 phase, but the mill absolutely requires 380v (3hp single-voltage, 2 speed motor). I could up the voltage from the converter, but the lathe has a single voltage 2 speed motor as well, and that one absolutely requires 220v. I'm probably going to underdrive the mill motor initially and eventually vfd either it or the lathe, or maybe both.

@Michel Auron You are probably correct about the back EMF causing the higher voltage, there's an extra stage of conversion necessary to boost the input voltage up, which as you rightly point out would increase the cost. I like the idea of getting a larger motor, although I've not really had an issue with power. Yet. I might investigate if it's possible to buy an off the shelf voltage booster (e.g a PFC front end that boosts 240v up to 440v) and pair that with a basic 3 phase input converter. So many ideas, so little time!

@@ollysworkshop So rectify -> dc boost -> synthesise waveforms? Sounds reasonable, I'm guessing that's how the 220 to 380 vfds do it. I'd be very interested in a video about your home brewed drive, actually.

I'll add it to the list! I'm working on my toolfest2021 'entry' today, or at least will be once the children are asleep. 🙄