# VFD?



## Lonsdale73 (3 Mar 2021)

I have a 1hp motor 'salvaged' from a (not at all) old lathe (Record Power DML320) which I was hoping to use it in a shop made dust extractor. As the lathe itself plugged straight into a regular 3-pin socket, I fitted a 13a plug to test the motor. It runs but it does get hot very quickly. Quick google search suggests it's because it is drawing too many volts. As the lathe was variable speed, do I need to include some form of resistor to allow it to run without burning out? If so, what should I be looking at?


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## Ttrees (3 Mar 2021)

Hello, presuming the motor is dual voltage, on the nameplate you might see 220,240 delta/D or a triangle symbol.
Is this the case where it might be best to go looking for a vector drive?

All I can say is the cheap VFD on my bandsaw (2 pole motor 2870RPM) didn't like being slowed down, and nor did the motor, so I would think you'd need a good inverter for the job.
Don't think a resistor for anything would be needed unless you want an emergency stop.

Tom


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## Sideways (3 Mar 2021)

This is a brushed motor which is driven from the mains via an electronic speed control.

It is not compatible with a "variable frequency drive" intended for ac induction motors. Wrong device.

I wouldn't try to use it without the original or a compatible speed control pcb, and I doubt that it is well suited to conversion to a dust extractor.

Brush motors are also termed universal motors. In principle they can be run off either ac or dc. Qualitatively, this is he same sort of motor used in corded electric drills. The speed contol will use a thyristor / triac type circuit like a high power version of a lighting dimmer.

Without information from the motor nameplate / manual / speed control pcb (electronic printed circuit board) I can't guess what voltage this motor is intended to run on and whether this is ac or dc. It is not safe to assume that it is suitable for direct connection to the mains without a working speed control.


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## Lonsdale73 (3 Mar 2021)

Does this help any?


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## guineafowl21 (3 Mar 2021)

It’s a 3/4hp, brushed universal motor, as far as I can see.

Rated speed is quite low for this type. A normal triac ‘dimmer’ speed control will, at the fastest setting, feed the power pretty much straight through. But as you found, doing so overheats the motor. 

This suggests that the factory fitted speed control has a range limit, or is not a triac type. Either way, the safest bet is to use the original controller if you have it.

How many wires does the motor have? I can’t tell from the Record site if the speed control is continuous or not, or if the motor has an inbuilt speed sensor.


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## Lonsdale73 (3 Mar 2021)

guineafowl21 said:


> It’s a 3/4hp, brushed universal motor, as far as I can see.
> 
> Rated speed is quite low for this type. A normal triac ‘dimmer’ speed control will, at the fastest setting, feed the power pretty much straight through. But as you found, doing so overheats the motor.
> 
> ...



It has three wires, one white, one green and a black as I recall


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## EddyCurrent (5 Mar 2021)

There is a manual here; https://www.willyvanhoutte.com/shop/downloads/PDF/DML320 Manual.pdf
It shows a basic electrical diagram.
There is a speed sensor, rotation direction switch, speed potentiometer but it's not clear if the speed sensor drives only the digital readout or if it's also part of a closed loop system for the motor speed control.

It also says this,

"33. Caution! Motor may become hot during use•
It is normal for motors on some machines to become hot to the touch during use.
Avoid touching the motor directly when in use. "



Lonsdale73 said:


> Quick google search suggests it's because it is drawing too many volts.



There's no such thing as that but it may draw too many amps if there is a fault.

It seems to me that if it's running on 240V 50Hz, it's speed is around 2900 RPM and it's taking around 3 Amps then it's likely to be okay.
Ensure the motor is well earthed though in case there is an earth leakage problem with it.


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## Peterm1000 (5 Mar 2021)

Shop made dust extractor or air filter? I just completed making an air filter using an 8 inch duct fan, a box and couple of panel filters - total cost about £70.


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## guineafowl21 (5 Mar 2021)

EddyCurrent said:


> There is a manual here; https://www.willyvanhoutte.com/shop/downloads/PDF/DML320 Manual.pdf
> It shows a basic electrical diagram.
> There is a speed sensor, rotation direction switch, speed potentiometer but it's not clear if the speed sensor drives only the digital readout or if it's also part of a closed loop system for the motor speed control.
> 
> ...


I wonder how hot it gets, and how quickly? I wouldn’t expect much heat from running unloaded on the bench.

Worth checking the brushes, and air vents.


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## mikej460 (5 Mar 2021)

When not under load it may be running too fast? Is this any use?

(1) How to Wiring Universal Washing Machine Motor - YouTube 

WINGONEER AC 220V 4000W High Power SCR Electronic Voltage Regulator Governor Dimmer Thermostat Speed Controller: Amazon.co.uk: DIY & Tools


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## Lonsdale73 (5 Mar 2021)

Peterm1000 said:


> Shop made dust extractor or air filter? I just completed making an air filter using an 8 inch duct fan, a box and couple of panel filters - total cost about £70.



Extractor


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## Lonsdale73 (5 Mar 2021)

guineafowl21 said:


> I wonder how hot it gets, and how quickly? I wouldn’t expect much heat from running unloaded on the bench.
> 
> Worth checking the brushes, and air vents.


 Too hot to touch in a very short time. For conparison, I ran the one fitted to a lathe for several minutes and casing remained COLD to the touch.


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## guineafowl21 (5 Mar 2021)

Lonsdale73 said:


> Too hot to touch in a very short time. For conparison, I ran the one fitted to a lathe for several minutes and casing remained COLD to the touch.


The motor might have to be run with the speed controller, or is faulty.

Get one of these:








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... and run the motor through the speed controller of the lathe, starting at lowest speed. Monitor the wattage, and if it exceeds the 550W rating well before full speed, switch off and throw it in the bin.


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## Lonsdale73 (6 Mar 2021)

guineafowl21 said:


> The motor might have to be run with the speed controller, or is faulty.
> 
> Get one of these:
> 
> ...



I've not long got the lathe back after it sitting in RP's service dept for 4 months so a little reluctant to mess about with the wiring. I - perhaps foolishly - thought it would be a relatively straightforward matter, Mathias always makes it look so easy.


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## guineafowl21 (6 Mar 2021)

Lonsdale73 said:


> I've not long got the lathe back after it sitting in RP's service dept for 4 months so a little reluctant to mess about with the wiring. I - perhaps foolishly - thought it would be a relatively straightforward matter, Mathias always makes it look so easy.


What about stripping the motor down, or at least look at the brushes. Might be something simple.


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## Lonsdale73 (6 Mar 2021)

I'll have a look but doesn't appear to have much to strip down. I'm 99% confident the motor itself is fine, it was only two months old when replaced and turned out it wasn't the problem, the controller was. I guess the controller has some bearing on the overheating. Like I said, having watched Matthias use motors from anything and everything, from old fridges, washing machines to air conditioning units, I thought it would be as straightforward as attaching a plug.


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## guineafowl21 (7 Mar 2021)

Lonsdale73 said:


> I'll have a look but doesn't appear to have much to strip down. I'm 99% confident the motor itself is fine, it was only two months old when replaced and turned out it wasn't the problem, the controller was. I guess the controller has some bearing on the overheating. Like I said, having watched Matthias use motors from anything and everything, from old fridges, washing machines to air conditioning units, I thought it would be as straightforward as attaching a plug.


Mr Wandel is a very versatile engineer. There’s an awful lot of knowledge behind what he does.

I think you’re right, in that the motor has been designed for use exclusively with the controller. As I said above, the rated speed is low for this type. Universal motors like that, if run without a load or controller of some type, usually rev themselves to bits on the bench.

If I were you, I might salvage a vacuum cleaner speed controller, or have a look on ebay for a triac-type motor speed controller. You’d need some kit to check it’s running according to spec.

Can you find a spare original controller? Or at least get some decent pics of the board of one you have?


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