ACDC Drives VFD

Has anyone bought one of the inverter and motor packages from ACDC Drives?

I am interested in the Motor Control Kit-AC10 Inverter 0.75KW 230VAC input

This has an inverter and 1hp 3 phase motor.

It is for the powered turntable on my (telescope) mirror making machine. It is currently powered by a 1 phase motor from Machine Mart which has worked fine but is very noisy and I would like to have variable speed. Also, occasionally the torque seems to be lacking and I have to help the turntable along by hand.

I have belts and pulleys which reduce the 1500 rpm of the motor to around 28 rpm for the turntable. I want to be able to change the speed between 1-2 rpm to around 40..

The Motor Control Kit is described as 'plug and play' which is good as I don't know much abut electronics. I managed to wire up the DOL starter and existing motor but it took a week or two of reading

David

Do you have a reason for choosing ACDC drives? Similar good quality packages are available from the likes of Transwave, Newton Tesla and others. They appear to beat ACDC on price too.

Mike

Your anticipated speed range looks too big to be accommodated by a VFD - especially if you are already using more than 750W at times (assuming here tht your present motor is ‘rated’ at that power. This is, of course, assuming the current motor is delivering that power - which may not be the case.

I’m not sure that torque is relevant in your calculations.

Not your specific equipment, but I bought a Sprint Electric DC drive from them for work a year or so ago & they were very efficient to deal with - very quick replies to pre-purchase queries & fast delivery. I had a new drive on site in 2 days from first enquiry & should I have another DC drive go down they would be first port of call.

Nigel B

Looking at two sites the ACDC offering is more "industrial" than the Newton Tesla one. Things like flexible conduit for the cables, control pendant apparently bought in from an industrial supplier, wider range of motor mount styles etc all help nidge the cost up but make things easier for industrial users. Newton Tesla have a jog button on their pendant which can be very nice in the right circumstances if well implemented.

Realistically the ACDC kit looks to be as close to "everything in the box, plug and play" as you can reasonably expect to get for an industrial user. For an industrial setting Newton Tesla is more "all the main bits, some installation parts assembly needed". Not sure how the industrial folks would view the simple stop button on the Newton Tesla pendant as against the safety mushroom style on the ACDC version. Newton Tesla kit will be fine as is for any home user where sensible installation is all you need for safety. Industrial folk have more stringent regulations to follow. For good reason.

Smaller motors and VFD boxes are pretty much commodity products these days. Both appear to use similar lower side of mid range industrial quality motors and VFD boxes. Appropriate for all ordinary applications. Need to check motor speed offered. Two pole, 2,800 rpm nominal, motors are cheaper but I've always advocated paying a bit more for 6 pole 1,000 rpm nominal motors as torque holds up much better when set to lower speeds. With retrofits its very rare that you need serious power at much higher than standard speed. Something to seriously consider as you mention an occasional shortage of torque

Best advice I think is to choose the package with the best control pendant for your needs. That's the bit you will be using all the time. In objective terms the price differentials between all reputable suppliers aren't huge so its silly to put up with something you find hard or annoying to drive.

Clive

David

With a range of such low speeds (2-40rpm) I believe you need to look into a reduction gearbox driven by a VFD controlled motor, an alternative drive would be a DC motor which also have good speed control capabilities.
This will ensure good torque at low speeds.

Emgee

double post, please remove

Edited By Emgee on 26/02/2020 20:49:53

Actually I already have a 30:1 reduction gearbox for my existing motor, the input is for the 14 mm shaft which is on my existing motor. I have not fitted it yet because I am not at the stage when I need really low rpm on the turntable-this is only needed in the last stage of working on the mirror, which I am almost at.

If I get a 1 hp 3 phase motor with a 19 mm shaft is it possible to buy (or make) an adapter to reduce it to 14mm so it will fit in the gearbox?

I have discovered that the v belt from the motor pulley was a bit slack and this was causing a lot of the noise, it is a step pulley so I have now put the belt on bit a bigger pulley and it is tighter and the machine is still noisy but not as bad. The speed of the turntable has now increased to around 38 rpm which is fine as it means the mirror gets polished faster.

I think I will think about this and possibly buy a VFD and 3 phase motor later in the year. I was going to buy from Newton Tesla, the AV750 I hp package. But when I rang them they told me that it could take up to a week to be delivered. I am on holiday next week on Monday and Tuesday so wanted to get it by then.

There are books in the workshop practice series about electronics and VFD so I will probably buy these and have a read.

David

If the gearbox you have is intended to have a flange mounted motor fitted directly to the gearbox you may find the motor frame type required on the gearbox nameplate.
If it is driven from an external shaft/pulley there shouldn't be a problem to get the required Oldham or similar connector.

Emgee

The ratio you mention would mean you have a 53.57 to 1 ratio. To run your turntable at 2 rpm will mean the motor will be running at 107 rpm. I run my inverter as low as 1.5hz for jog. But it does not have much torque at that figure. But the torque rises pretty quick with the higher frequency. If I have time tomorrow I will run mine slow & see what the torque is like. There is a calculation for all this but cannot remember any more. To run it at 40rpm you would then need to overdrive the VFD to give a motor speed of 2120. Which is no problem for a 4 pole motor. The basically same frame as the 2 pole which runs at 2800 anyway.

Steve.

My existing gearbox is for a 71 frame motor, the 3 phase motor I am planning to get is an 80 frame motor, and the shaft on the motor is 19 mm rather than 14 mm on the existing motor, so it won't fit.

What I was wondering about was, if I got a 30:1 gearbox for the new motor this should make everything fine for very slow rpm for the turntable of between 1-5. But would the VFD and the motor be able to increase the rpm of the turntable to 40 rpm with this amount of reduction?

Perhaps I would be better with say 15:1 reduction? I have 3 shafts with pulleys on to reduce the rpm, so I could change the machine if necessary to only use two of the shafts, which would increase the speed.

At the moment I will not need that much torque when the turntable is running at low speed. This is because at that stage I will be pushing the polishing lap across the mirror by hand.

The torque is needed when the lap rotates on the machine in a fixed place. However, eventually I would like to add a powered overarm so that the machine would push the polishing lap back and forth across the mirror. I could possibly use my existing motor and gearbox for this, it is better not to run the overarm off the same pulley system as the turntable but rather to have a second motor.

David

Do remember in thinking about changes that as you alter the ratios to increase speed, you also reduce torque. Always.

Having said that, I wonder why you are having to help your existing system along, as with the reduction on a 1HP motor you have you should be able to tow tanks out of bogs, but slowly. It sounds as though you have a lot of friction somewhere. This is also a cause of squeaking V-belts - a common problem with old cars on cold mornings, as the alternator drive takes power to top up the battery but the belt is old, or slack, or usually both.

Using very low speed from a VFD does not just lead to lower torque than you might expect, it also reduces the cooling effect of any fan in the motor. So as well as poor torque you can get overheating, especially on jobs like yours which can go on and on for hours.

Regards, Tim

Edited By Tim Stevens on 27/02/2020 17:26:12

My existing motor is single phase 1/2 hp. I am only thinking about getting a 3 phase 1 hp motor.