Chipmaster vfd

Hi all have been given a chipmaster with a noisy variant soo changing to vfd I'm after advice on the motor and invertor I have to know of I should change the configuration to start or delta many thanks

The output from the inverter is stated as 220v 3 phase so you will need to make sure the motor is connected in delta form.

Emgee

For info as question has been answered.

Star configuration is always for 415V motors (as far as I am aware). Delta, is for 220V supply - and as far as I know, 220V three phase motors are not produced in star configuration.

They are (nearly?) all made to be easily reconfigured for either because it is so simple. Most are supplied as star, unless specified, as connecting a star motor to 220V will not destroy the motor, but 415V to a delta configured motor would likely ‘let the magic smoke out’ in short order.

Further some early motors were made with the star point within the motor body and most of these can be converted to star/delta by locating and splitting the star point and bringing the separate wires to a connection block where they can be configured in either way.

'Fraid thar ain't the whole answer.

Bigger motors - say 4KW and up - are generally wound 400v (delta) and therefore 690volt (star).

This lets them be used with a star delta starter. This applies the line voltage (400 volts three phase) to the windings connected in star to accelerate the motor from standstill to about 80% speed.  The starter contactors then switch the windings into delta configuration and re-apply the supply, to achieve full speed and power.

The advantage is that the maximum inrush current Is reduced to about three times the full load current, and the machine gets a gentler start.

Even bigger motors  apply the same principles at higher voltages (3.3 KV for example).

So it all depends on the application.

Edit - rephrased for clarity - hopefully

Edited By Simon Williams 3 on 25/05/2020 08:54:34

The confusing thing for me says the output 0to 240v and 0 to 400v so wasn't to sure what one to use the invertor manual doesn't state I see slot of people seem to use delta configuration

The application is to get rid off the mechanical noisy variant of my chipmaster and replace with this set up and a pendant with a speed control to vary the speed

Sorry new to this many thanks

What power supply is the lathe running on at the moment? (Voltage) If it's 230V, the VFD can be connected as is.

The motor plate says your motor can be configured in either star or delta (hurrah!), but you'd have to look inside the terminal box to find out which it's set up for at the moment. The motor needs to be configured 230V Delta to match your VFD, and it might be ready to go already. No harm done if a 230V VFD is connected to a motor that's configured in star Y for 400V. The motor will just be underpowered, and that's fixed by swapping a few terminal connections. The risk of magic smoke is low!

With luck there's a circuit inside the terminal box explaining how to connect the motor in either star or delta. If not post a photo of the terminals; the forum has some motor experts who know their stuff in detail.

Dave

Edited By SillyOldDuffer on 25/05/2020 09:22:30

Sean the plate on the vfd says 0-240v, 0-400 HZ not 400 VOLTS.

Ah, that's a misreading of the VFD data. It's 0 to 240Vac and 0 to 400Hz. The first is the voltage, the second gives the VFDs maximum speed range, which is fine.

I agree with Simon, NDIY's description, while correct (bar the minor issue that 220 V P-N is 380 V P-P not 425 V) for a lot of the 3 phase motors on smaller machine tools, is not the whole story .

It's important to realise that the voltage rating of the individual motor windings does not change between star and delta connections. Think of Star as series connection and Delta as parallel. This is easier to understand if you think of a single phase motor with two 120V windings connected in parallel for 120 V. It's easy to understand that if you connect the two windings in series it will run on 240V at the same power, you just multiply by two. For a multiphase connection the indivudual winding voltage rating is the Delta (phase to phase) voltage and the Star voltage is the winding voltage multipled by the square root of the number of phases which is 1.732 for 3 phase. Hence a 240 V winding voltage motor needs to be wired Star for the UK standard light industrial 3 phase supply of 415 V phase to phase. If a 240 V winding motor is wired delta the phase to phase voltage has to be 240 V which is non-standard and would give a phase to neutral voltage of 138 V.
It is much easier for a single phase input VFD to generate 240 V phase to phase (138V P-N) than 415 V.
The reason small motors are designed to be wired star (240 V winding voltage) is because fewer turns are needed making it cheaper to manufacture (with big motors the thinner wire of a 415V winding becomes an advantage). It's a lucky coincidence that it allows simpler and cheaper VFDs.

Robert G8RPI.

Sean,

If you wish to sell the variator, I would be interested, along with any of the control gear that is now redundant.

Please drop me a message.

Thanks.

Sean

One often overlooked issue when changing from variator to VFD drive is speed range. Typically variators, and the functionally equivalent expanding - contracting pulley Reeves drives, have a theoretical speed range approaching 10:1 from fastest to slowest. In practice 8:1 seems to be more like what you can actually use.

For all sorts of complicated physical reasons induction motor torque, and therefore power output, falls off when you try to operate too far off its design speed. Big surprise. Not!

In practice modern motors and good brand VFDs will run between about ± 1/3 rd of the nominal speed range with minimal effect on power delivered to the spindle. Call it 40 to 70 Hz from the VFD, although as most modern motors are 50/60 hz devices 40 to 80 is reasonable. There will be some drop off in torque at the low end but variators aren't exceptionally efficient devices, Reeves drives are even worse. A simple belt drive is more efficient so odds are you will get the power back simply from lower losses.

Generally, with modern equipment, and a little bit of thought as to gear ratios you can do just fine over a 4:1 speed range. You will loose out a little on power, most likely at the lower end, but the results are usually satisfactory for home use.

Especially as you are unlikely to drive the lathe in a manner that needs its full power.

As the price differential between 6 pole "1000 rpm" and standard 4 pole "1440 rpm" motors has narrowed so much in recent years I tend to advocate using a 6 pole motor to get more oomph at the low end. Generally high speeds are for small work so the power you can use before pretzelling the job is limited. Alternatively a larger 4 pole motor can be used to get more low speed torque but these days that, including the bigger VFD, tends to be a little more expensive. Modern vertical mills take the larger VFD controlled motor idea to extremes with monster, by old style multispeed gearbox or belt drive standards, motors to give a wide speed range whist keeping plenty of low speed drive.

The most satisfactory way of dealing with the conversion is probably to incorporate some sort of two speed primary drive into the system. Nominal 4:1 on the VFD and 2:1 on the primary would match the variator performance nicely. An external lever control for two speed gearbox or twin drive belt selection would be neat but in practice shifting by hand ought to be fine as the VFD control range will let you overlap pretty happily when you need to go a bit out of the preferred range. Annoying to keep opening the door tho'.

I'm surprised that no one has published a design for a simple remote mechanical change 2 speed unit for this sort of thing. One day my Varispeed Bridgeport will get changed for a VFD drive. I have a nice solenoid opearted 2 speed gearbox off a very old washing machine that might do. Or maybe get creative with the electric clutches used in car air conditioning systems.

Clive

Hey,

I've often seen this modification arising around chipmaster owners. I don't know if it's too late, but if you haven't done the modifications yet, could you make a recording of the noise so we can learn from it?

Most of the times, the bearings are worn out in the variator. There are only four bearings in it! And in some odd cases only the oil needs to be topped up. This was in my case when I got the lathe and it ran fine ever since.

Older chippies have the motor mounted in direct contact with the base of the lathe. This amplifies the motor/variator noise levels and they are noisier than the newer types which have rubber on the motor/variator mount that reduces noise levels quite a bit. Which one is yours?

As it sound like, yes, I am anti VFD. The variator lasted for a few decades, and it was designed for such a purpose. It has quite some weight and when all this weight is tunning makes machining smooth by absorbing forces. Won't you loose all that if you go to a VFD?

Don't want to rant here, just curious.

Tiger

My Chipmaster still has the variator installed and I have installed a VFD, I tend to use the variator for coarse and the VFD for fine speed adjustments.
The rubber mounts were replaced last year. The variator certainly isn't quiet, but it is 57 years old (assuming original) Whether the noise is "normal" I have no idea. I will see if I can get recording for you.

Recording of variator in action.

As mentioned above may lathe does have a VFD. For this test the VFD was set to 50 Hz.
Clutch is not engaged so the only noise is motor, variator and clutch shaft. Variator adlustment was a bit sticky at bottom and top end as I don't often go there!

**LINK**

Those variators should have an adjustment for the cones. Yours might only need adjusting.