2nd-hand Sedgwick PT255: single to 3-phase converter advice

[Iancd]

Just bought an old (1980s..?) Sedgwick PT255 Planer-Thicknesser
It's a three-phase machine which I'll be using on a domestic single-phase supply.
I've begun reading up on what's involved today... my brain started hurting with these - https://en.wikipedia.org/wiki/Delta-wye_transformer, https://en.wikipedia.org/wiki/Y-Δ_transform, http://phasetechnologies.com/phaseconverterinfo/phaseconverter_vfd.htm

...but I think I've gleaned that I have a choice between using a 'rotary' (e.g. 'Transwave') converter, and a VFD set up as a converter. I understand the rotary device will be noisier..? I have to get a device with sufficient capacity... higher capacity may be useful in future, to have option of running another three-phase machine, but obviously would come at a cost.

Details from motor plate:
Hawker Siddeley
Brooke Crompton Parkinson Motors
A.C. Motor BS 5000/99
IP54 220031
Frame / No. D90S | Q693905
Class: F Rise: 8 Diag: B
kW: 1.1 Rev/min. 1420 RTG: MCR
v: 240/415 followed by Delta and Y symbols (second ‘Y’ symbol is upside down - ? means ‘star’ - apparently, these symbols are concerned with delta-Y or delta-star wiring of the motor..?
PH: 3 A: 5.2 / 3.0
Made in England MA2

Any advice on what I need and could buy at reasonable cost, say £200 max. though substantially less if that's feasible without jeopardising satisfactory running / performance of the motor..?
I'm also a bit put off by some of the reports of the noise associated with the rotary type... though I'll be wearing ear protectors the noise of the machine - plus dust extraction and yet another motor - and the potential impact on neighbours and others in the house is a concern..!
Ian

 

[kinsella]

Ian
I post this last week, it may help.

3-phase-to-single-phase-startrite-275-conversion-from-3-ph-t91106.html

 

[TFrench]

I've done this with a morticer, and ended up going the VFD route, mainly because it gives easy speed control and I actually understand what its doing! You have to wire it in directly to the motor though so you wouldn't be able to use it on anything else. I'm not entirely sure why you can't though - I'd like to hear a good reason from someone cleverer than me with this kind of thing! Kinsella's post is very helpful as well.

 

[MusicMan]

I have three 3-phase machines that I run off VFDs: a 2 HP metal lathe (Boley, 1930s), an Arboga 1 HP miller (1950s) and a Wadkin AGS saw (2 HP, 1960s). All 415 V which does limit the cheaper solutions. After going to and fro as you have done I bit the VFD bullet from Drives Direct. Not cheap: £300 for the 1 HP and £400 for the 3 HP. But I am glad they did because they work SO well, and they have resale value. And Dave from the firm is extremely helpful and patient with DIY installers and will talk you through any problems. The only real one I had was on the oldest machine, which at first would trip the power circuit trip on the consumer unit when getting up to about 10% speed. I had previously seen this working on a noisy rotary converter. He suggested that it was caused by the windings accumulating damp and that they just need drying out, e.g. in the regular cooking oven. The motor was too big and heavy for this so I rigged up a fan heater aimed directly at the motor and heated it up, gradually running faster, over about 2 days. This indeed fixed the problem; it recurred at a higher speed about 3 months later but after another heat soak it has been fine for about 2 years. The control is fine and reliable, and they are easy to program to stop within less than 10 seconds, and also have a DC brake. A nice touch is that the units stay powered up for 10 - 20s after the power is switched off (presumably a big capacitor) which gives you braking even if the mains is interrupted. And all three run from a normal 13A socket.

 

[memzey]

I think the problem with doing this on a planer thicknesser is that they often have two motors - one to drive the cutter head and the other to drive the feed rollers. As each motor would require its own VFD a rotary or static phase converter is likely to be the most economic option. I don't know whether the machine in question is a single or dual motor variant but if I were buying one that would be the first thing I'd check.

 

[MusicMan]

Yes that would not be economical for two motors.

 

[Iancd]

Thanks for the responses, folks.
Kinsella, that was really helpful - particularly the link to R Minchin's paper on motors. I need to re-read it, but although he doesn't refer directly to 'VFDs' as such, I take it this is what he's describing in the section on single to three phase inverters.
As the advice here is consistent - and it is just one motor in this machine - that's the route I'll go: back to eBay / Drives Direct.

 

[memzey]

Ok. As this machine is single motor and is wired for dual voltage you can configure it to 240v which means you can get one of the much cheaper VFDs that don't have a step up transformer. I like the Sedgewick PTs they are very well built. Does yours come with the extended in feed table?

 

[Iancd]

Ok. As this machine is single motor and is wired for dual voltage you can configure it to 240v which means you can get one of the much cheaper VFDs that don't have a step up transformer. I like the Sedgewick PTs they are very well built. Does yours come with the extended in feed table?

Hi Memzey,
No, it's actually got short infeed and outfeed tables - I've asked for some advice about supporting longer workpieces in my other current post: https://www.ukworkshop.co.uk/forums/yet-another-planer-thicknesser-question-t90911.html
Kenneth: I've just bought the same inverter as you from Motor Control Warehouse, so thanks again for the tip. There were cheaper options available but only with IP20 protection, so that was the way to go. Jez at MCW also offered to talk me through any wiring issues if I need him to, particularly regarding connecting the stop / start buttons on the Sedgwick. The inverter should arrive tomorrow.
Ian

 

[kinsella]

Ok. As this machine is single motor and is wired for dual voltage you can configure it to 240v which means you can get one of the much cheaper VFDs that don't have a step up transformer. I like the Sedgewick PTs they are very well built. Does yours come with the extended in feed table?

Hi Memzey,
No, it's actually got short infeed and outfeed tables - I've asked for some advice about supporting longer workpieces in my other current post: https://www.ukworkshop.co.uk/forums/yet-another-planer-thicknesser-question-t90911.html
Kenneth: I've just bought the same inverter as you from Motor Control Warehouse, so thanks again for the tip. There were cheaper options available but only with IP20 protection, so that was the way to go. Jez at MCW also offered to talk me through any wiring issues if I need him to, particularly regarding connecting the stop / start buttons on the Sedgwick. The inverter should arrive tomorrow.
Ian

Ian, like all the posts on the subject i thought i'd do the post so it helps others or at least point them in the right direction. It took me a while even with all the posts on the subject to get my head around it. So glad you found it helpful. Happy to deal with any questions when you get it. Just PM me, they tend to pop up on my phone.

 

[Iancd]

I've sorted the wiring and the planer is now working
Gareth at Motor Control Warehouse was extremely helpful, talking me through setting various parameters on the inverter to get it working as I needed.
Here's what I've done - set out in some detail, in case it's useful to others (clicking on the pics brings up bigger versions).

Planer connections
I'm running the planer motor, which is dual 240/415v, on three phase 230/240v supply from the inverter drive. Connections at the motor were changed to low voltage (delta) configuration as detailed in the inverter manual and on the cover of the motor terminal box.

The original Brook Crompton control gear (NVR switch) on the Sedgwick was (presumably) designed for three phase supply and was rated 380/415 volts, so I needed to replace that. I wanted to retain control of the planer at the machine, rather than at the inverter.
I used the original heavy duty, shielded, power cable for the planer to connect the motor to the inverter. The cable shielding is connected to the gland plate at the Inverter (IP66 version), and to the motor bracket at the planer; the planer is also earthed via the new NVR switch so I think this should take care of the EMC requirements.

---

I used one of the mounting holes for the original switch unit and drilled a new one (6mm) as the old switch unit was bigger. Power to the switch comes in at left, and goes to the inverter at right, through the planer framework from the switch and out at the back; this is following the same route as the original internal power cable to the motor from the switch.
This was the method Gareth recommended: the NVR switch connects and interrupts the power supply to the inverter and the planer starts and stops in response. I don't have to touch the inverter, which is mounted on a wall near the planer, at all.

Incoming supply and inverter power earths are connected to the planer body. NVR switch from Axminster, wired as per the download document on their site, here: http://www.axminster.co.uk/media/downloads/200093_TechnicalDataSheet_1.pdf

Inverter connections and parameters
To have the inverter start the planer as soon as it is powered on, the inverter needs to be set up for terminal, rather than keyboard, control; there are - at least - a couple of ways of doing this, which Gareth talked me through; I chose the easiest..!
This inverter is a complex and very capable piece of kit which I'm using in a very basic mode - seems a shame in some ways but it's all I need it to do; makes me wonder if there was a more basic inverter that would have done the job, but I didn't find one with an IP54 or IP66 rated enclosure (ok for dust and moisture without having to house it in a separate enclosure), nor at a better price.

Power supply to the inverter, from the NVR switch on the planer, coming in at left. Power from the drive to the motor at right, with the (earthed) cable shielding connected to the gland plate.
Terminals 1-2 and 5-6 are connected to each other; this is explained below.

Before making any terminal connections the following parameter checks and changes were made:
P-01 Max. frequency / speed limit: left at default = 50.0 Hz (frequency generated by the inverter in Hz determines the RPM of the motor: a 4-pole motor will run at 1500rpm at 50Hz. This is useful to know regarding the effect on 'motor slip compensation' of changing P-10, motor rated speed, from its default value of 0; see the paper by RC Minchin, which Kinsella has linked to in his post, for more detail)
P-02 Min. frequency / speed limit: left at default = 0.0 Hz
P-03 to P-06 - control of starting and stopping times, stopping mode, and energy optimisation - all left at default.
P-07 Motor rated voltage: left at default = 230V
P-08 Motor rated current: set to 5.2A as on motor plate
P-09 Motor rated frequency: left at default = 50.0 Hz, as on motor plate
P-10 Motor Rated Speed: left at default = 50 Hz.
If I'd reset this to 1420 as on the motor plate, this would have enabled the 'motor slip compensation function', which Gareth explained to me: the drive would have detected when the motor speed slipped under load from 1500rpm to 1420rpm and would have increased the generated frequency to compensate for this and bring the speed back up to 1500rpm. All speed parameters would also be shown in rpm. In fact I did try this but couldn't get the speed displays to be in rpm and I don't know if the motor slip function would have worked. I think this must have been because of the order in which I made changes, including the control terminal connections. I decided to just leave it at default, In any case, I don't know whether bringing the motor speed back up to 1500rpm under load would be a good thing for the motor and planer, and bearings, though the 80rpm is only a very small increase so I doubt it would have have much effect, if any.
P-11 voltage boost --> default
P-12 Primary Command Source Eventually left at default, 0 = Terminal Control. Temporarily changed initially to enable control from keypad to test motor connections, to 1 = Uni-directional keypad control

Control terminals 5-6 are then connected. This is providing a 10v analogue input to the drive, in place of connecting a potentiometer across terminals 5, 6 & 7, which tells the drive to run at the (parameter P-01) maximum speed.
And that's all that's needed to run the drive as I wanted.
Gareth did talk me through an alternative way of doing this, which I also used initially, of enabling the extended parameter set and using P-30 and P-31 with keypad control on first start-up, to test motor connections. That was useful as the motor ran in reverse at first..! The motor terminal connections weren't as I'd anticipated: U-V-W wires (white, black, brown) from the drive had to be connected V-U-W at the motor.
It ran forward once I swapped U and V at the motor, and I then simplified control by connecting terminals 1-2 and 5-6 as set out above.

As I said, the planer is now working. I do need to get or make a main guard for it and add some extended feed support - I'll try Roger S's design at both infeed and outfeed.
I also need to rig up a hoist and slings to the joists above it, so I can lift it up half a metre or so toward the ceiling when we get seriously flooded again - I just hope that doesn't happen for quite some time...!!

Thanks again for all the helpful input - really much appreciated. I now know just a bit about induction motors and variable frequency drive inverters - hadn't even heard of those a week ago..!
The bottom line is this works, which makes three phase machines viable for home workshops... Brilliant..!