Sustainability of under powered VFD on Initial motor starting

Hi All,

Thank you all for your comments. Bill has hit the nail on the head and replied accordingly and for that I am most grateful. Yes my device indeed is connected to a suitably rated circuit. One of the benefits of plug and play mode is as Bill has correctly pointed out... the ability to run more than one single voltage motor per machine, i.e. lathe drive + suds pump + Low voltage transformer for Men type light, + workshop ring main and in addition also allows me to take off a 240v volt supply for my newly installed DRO.

In addition because it has EMC filtering, and a sine wave filter installed it is capable of driving all the inbuilt contractors and any other electronics as required.

Cheers, Gary

Just a thought, are you running the motors direct from the VFD output or via the sine wave filter?

Andrew

Murray, these days it is an urban myth unless specifically mentioned in the VFD's manual. I have four VFDs in my shed. The big Danfoss, which specifically states "External load switching No limits". Two Altivar units of different families, in which the Only warnings are:-

Altivar 12 series:-

|RISK OF DAMAGE TO THE MOTOR
|The use of external overload protection is required under the following conditions:
|• Repowering up the product since there is no motor thermal state memory.
|• Running multiple motors
|• Running motors rated at less than 20% of the nominal drive current
|• Using motor switching
|Failure to follow these instructions can result in equipment damage.

Altivar 28 series:-

|The drive controller is sensitive to the amount of capacitance (either phase-tophase
|or phase-to-ground) present on the output power conductors. Excessive
|capacitance can cause an overcurrent trip.

I also have an 'ancient' IMO Jaguar cub that I got from Sir John. This, IIRC, did have a restriction on switching between the VFD and the load. I know these have been fragile in the past, but on the Myford, it doesn't need downstream switching. It's also 17 years old.

Those are the only examples I Personally own (and the Altivar 28 isn't in use yet), but I also base my statements on the knowledge of the limitations and advantages of GTO thyristors, MOSFETs and IGBTs.

The drive that Gary and Bill are using is sold as specifically suitable for this type of application.

Sorry to derail the thread further. My original comment was specific to the OP, not a general rant.

Edited By Mark Rand on 09/10/2018 23:21:04

Right Gary i am i think the only one on here that can give the honest true answer, that 5hp Invertor not a VFD is way under powered.

I had exactly the same scenario 8 years back to power an M300 2.2kw motor. I did buy the exact same invertor you have and it lasted 1hr 25mins, bye bye £600.

Remedy was to get the 10hp invertor, i paid £900 now well over £2.2k.

Whats happening the startup current is more like starting at least a 9hp motor, add on what ever the gear is in can be like trying to pull away in a car in 5th!
Even if you can get it running by givng it a push start, slightest cut put on will see the invertor constantly ramping up to a certain point where it will slow down. Thats with clean up cuts.

Same problem with a Transwave Convertor think 5hp? maybe more, except that was much worse, not even a menial cut 0.3mm could be put on in mid range speed without it deafening you and spindle slowing to a halt constantly.

Touch wood 7 1/2 years on the 7.5kw invertor is still running and used daily for several hours at a time, plus power the whole workshop. No need to remove and plug in each machine, theyre left permanently plugged in to 3ph sockets and can run several machines at same time.

Mark, the Jaguar Cubs are probably the commonest units in use by hobbyists these day, along with other, very similar, entry level units.

Most of these users really struggle with the huge manual and are unlikely to find the warning against load side switching.

Your units might be fine, but please don't encourage hobbyist to use downstream switching. It's only fair to err on the side of caution in these circumstances.

Neil

Detailed post deleted to avoid further disagreements.

Edited By Mark Rand on 10/10/2018 22:51:03