Motor Input and Output Power

[Michael GilliganParticipant @michaelgilligan61133]

Keep up the good work, Ketan

It may take a while, but honesty and integrity will win in the end.

Keep it simple and factual:

Get SIEG to certify electrical power consumption and mechanical power output [under clearly specified conditions], and then state both in your advertising … Let your competitors squirm when potential customers ask them to do the same.

MichaelG.

.

P.S. … Given that the linked SIEG document is basically a de-bunking of someone else's dubious 'test method' I think it is entirely adequate.

 

Edited By Michael Gilligan on 14/10/2015 17:25:06

[AjohnwParticipant @ajohnw51620]

TUV did get involved in fishing line some years ago. A commercial nightmare for both manufacturers and retailers. They actually published real figures. The hype in this area relates do line diameter and knotted and unknotted breaking strain even wet and dry. Very similar to your problem. In this case I would guess that eventually the manufacturers thought better to not head in that direction and just continue as usual. One particular make of line became weaker. They may still do this sort of thing on any product.

There are supposed to be advertising standards. I feel they are a bit of a joke in some areas. As a designer I have often been asked to rate a problem on the basis of who will notice it, expert, some one with limited knowledge of what ever it is or joe blogs etc. Then come conditions, likely hood, severity etc.That's life these days in many areas. Marketing is probably similar. I know sales are.

One thing that might not have struck you is companies might over state the motor power and not even allow the motor to run at that level. It's no worse than using input power as far as use of the machine is concerned. How on earth would a typical newbie to lathes know. They are probably completely un aware of the torque characteristics of electronic variable speed drive as well. That aspect in it self should make people wonder.

John

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[Russell EberhardtParticipant @russelleberhardt48058]

In the past Rolls Royce, when asked what power their car engine was would reply "Sufficient". That is surely what is needed for a lathe. Too much power could be worse than too little, over-stressing the machine.

Having said that, the best way to specify the motor power (IMHO) is to quote the maximum power output that can be extracted from the motor continuously. Much more power than that can be drawn from those little motors for a short time but with the risk of overheating if used for an extended period.

Russell

P.S. perfectly happy with the power output of the brushless motor on my SX2P mill.

Edited By Russell Eberhardt on 14/10/2015 18:55:06

[Ketan SwaliParticipant @ketanswali79440]

Posted by Michael Gilligan on 14/10/2015 17:21:33:

Keep up the good work, Ketan

It may take a while, but honesty and integrity will win in the end.

Keep it simple and factual:

Get SIEG to certify electrical power consumption and mechanical power output [under clearly specified conditions], and then state both in your advertising … Let your competitors squirm when potential customers ask them to do the same.

MichaelG.

.

P.S. … Given that the linked SIEG document is basically a de-bunking of someone else's dubious 'test method' I think it is entirely adequate.

Edited By Michael Gilligan on 14/10/2015 17:25:06

Hi Michael,

Thank you for the comments. I will work on this with the factory. They are currently at an exhibition and I will review various points with them, once they are back.

In the mean time, it seems reasonably clear that it is difficult to measure output power in the hobby workshop.

General question to anyone who can comment:

How difficult is it likely to be to measure input power in a hobby workshop, safely ?

After reading the various comments, the issue of efficiency has been raised, ranging from 63% to 80%.

So far, as a simpleton, input power is always greater than output power. So, if input power can be measured in a simple way (pictures if possible please), then it is written that the output power – first at the motor end will be lower, then further reduced by the speed control (as Les Jones suggested in a conversation with me today), followed by mechanical elements in the chain, based on efficiency.

If this were possible, could I suggest this to anyone who says to me 'but mine is better than yours' with reference to motor power?

Ketan at ARC.

[Neil WyattModerator @neilwyatt]

I'm sure there will be a haillstorm of criticism, but one of THESE will be more than adequate for giving a reasonable estimate of input power for any device you can plug into it.

The most useful measure of actual output power is to stick in a big, new tool and see how fast you can chew metal with it. THIS calculator can help. The sums will work for lathes as well as mills.

My lathe came very close to its rated ~0.5Hp when I did this test.

Neil

[CotswoldsPhilParticipant @cotswoldsphil]

Neil, Ketan

The power meter you link to is very similar to the one I use on the lathe to watch the power consumption. Works very well – I generally keep it set to amps to see the current reading. But set it to kwh when I have the heating on overnight.

Phil

[Gordon WParticipant @gordonw]

Those power meters are very useful, I usually have it on amps for the heat pump, also for the water pump, shows when it is stopped-as remote indicator. Very interesting checking peak values ie. on start-up. Also can show power factors, can be revealing. If you really want to check quoted inputs/outputs try buying a small generator, a real can of worms.

[Bill DawesParticipant @billdawes]

These topics are interesting. As a long time user of industrial motors (Brook, Siemens, ABB, WEG etc) I take quoted motor power at face value, ie it is power output (in kw) input (in amps) being stated on the nameplate.

Will look at power ratings on non industrial stuff more closely in future.

Bill D.

[AjohnwParticipant @ajohnw51620]

Posted by Neil Wyatt on 15/10/2015 15:37:50:

I'm sure there will be a haillstorm of criticism, but one of THESE will be more than adequate for giving a reasonable estimate of input power for any device you can plug into it.

The most useful measure of actual output power is to stick in a big, new tool and see how fast you can chew metal with it. THIS calculator can help. The sums will work for lathes as well as mills.

My lathe came very close to its rated ~0.5Hp when I did this test.

Neil

I recollect that ordinary electricity meters gain for the supplier when the power factor is out.

We just had one with 4g in it fitted ???????????? I wonder if that one is better or worse from the user end.

John

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[egaParticipant @ega]

Neil Wyatt:

Do you happen to know whether those Power Meters can be used with a VFD? (ie Power Meter in domestic 13A socket and lead to VFD plugged into Power Meter).

I have a similar device from Maplin which I use to keep an eye on the power consumption of my PC.

[john fletcher 1Participant @johnfletcher1]

Yes, the inverter can be plugged into the power meter, I have had one several years now. Mine will measure Volts, amps power factor, Kw, Kwh and you can set the tariff as well, so that you know how much it cost to run your heater, lathe etc. I think Aldi or Lidl had a similar gadget some time ago, worth having. John

[Roger HeadParticipant @rogerhead16992]

[quote]

I recollect that ordinary electricity meters gain for the supplier when the power factor is out. [/quote]

Once upon a time it was the supplier who lost out. The meters were specifically designed to measure true power i.e. the product of the supply voltage and the in-phase component of the current. The supplier lost out by virtue of incurring the cost of losses involved in the generation and transport of higher currents for the same end-user chargeable power.

There was always the push for the user or equipment manufacturer to fit PF-corrective devices.

But I haven't kept up with modern meter design, so I'd be interested to hear from anyone who has definitive knowledge.

Roger

 

Edited By Roger Head on 18/10/2015 01:40:46

[John HaineParticipant @johnhaine32865]

I recall when I was at university I made a little charger for nicads that had a rather cheap transformer, and when we plugged it into the mains with no other load, the coin in the slot meter went backwards! However the meter designers had obviously realised the potential problem and put a ratchet between the disc and the counter…

[MuzzerParticipant @muzzer]

Hi Ketan

Just consider yourself lucky not to be competing in the US / Canadian market. There it seems you can just pull spec numbers right out of your 4ss and get away with it. "Marketing genius" must be defined there in terms of how outrageous and preposterous your claims are. There are clearly no effective advertising standards regulations.

Take a look at this page of wet and dry vacuum cleaners. Although they are all fitted with std 115V plugs (12A continuous, 15A peak), the marketing genii seem to have come up with a scheme to differentiate the different models by means of "peak HP". The top end machines claim to have motors that are "6.5 peak hp". You don't need to be much of an expert to figure out that the peak electrical power you can get through such a plug is 115V x 15A = 1.7kW or 2.3 hp in old money.So quite where the remaining 4.2 hp are supposed to materialise from, god only knows. Presumably out of the same place mentioned above. Most punters aren't going to have a clue that they are being sold a pup but the toothless advertising standards jobsworths shouldn't be allowing the manufacturers to get away with it.

Motor efficiency is defined as mechanical shaft (ie output) power divided by the real component of the electrical input power to the motor. If a motor is sold as a 3kW machine, it should be able to provide 3kW of mechanical power. Obviously it will require 4kW or so of electrical power to do so and the name plate may indicate the voltage and current at rated output. As the power factor isn't going to be unity, the currents and voltages will not be exactly in phase. This means you can't simply multiply them together to work out the input power.

Measuring the real component of motor current and voltage (and hence efficiency) when driving a motor from a VFD takes very expensive equipment due to the high frequency switching voltages used. You need a very high sampling frequency and deadly accurate measurement sensors. However, placing a standard 50Hz power meter on the input of the VFD will give a pretty good measure of the input power. The losses in the motor are much higher than in the VFD but you don't need to know how the losses are spread between the motor and VFD.

For a machine tool, you might specify the useful shaft power of the motor used and also the maximum current draw that it will take from the mains – can't imagine what else you would need to know. Cynically or ignorantly conflating them is just shoddy and / or dishonest and marks out the cowboys from the reputable dealers. However it puts the good guys and the punters at a disadvantage and should be stopped.

Murray

[Neil WyattModerator @neilwyatt]

Posted by Muzzer on 18/10/2015 09:44:45:

Measuring the real component of motor current and voltage (and hence efficiency) when driving a motor from a VFD takes very expensive equipment due to the high frequency switching voltages used. You need a very high sampling frequency and deadly accurate measurement sensors. However, placing a standard 50Hz power meter on the input of the VFD will give a pretty good measure of the input power. The losses in the motor are much higher than in the VFD but you don't need to know how the losses are spread between the motor and VFD.

Very true, but any VFD worth its salt will have that electrickery inside it and be able to tell you its instantaneous output power. I have mine driving a little analogue meter on the front of the lathe so I can see exactly when and by how much I am overloading the poor beast.

Worth nothing, though, that the brushed machines in this debate don't have VFDs, they just have PWM DC drives.

Neil

Edited By Neil Wyatt on 18/10/2015 10:08:24

[Michael GilliganParticipant @michaelgilligan61133]

Neil,

I'm disappointed to see the scaling on your % POWER meter.

… Would have expected it to read to 110%

MichaelG.

[Neil WyattModerator @neilwyatt]

The Marshall Lathe

To be honest, I can't remember how its calibrated , FSD is over 100%, as that is the continuous rated power and it can deliver more than that, but FSD might be 150 or 200% – I will have to check the scaling some time…

<edit> Just read my own article: "There are two indicators, a yellow LED showing the inverter is live and a power meter indicating 0-10, 5 is 100% of nominal power."

 

As an interesting adjunct to this debate, my Vox Valvetronix VT20 is sold as a 20W guitar amp, but when you see the paperwork, it actually has a rated maximum output of 30W RMS! Do you think I should ask for my money back?

Neil

Edited By Neil Wyatt on 18/10/2015 10:43:12

[Chris DentonParticipant @chrisdenton53037]

Posted by Ketan Swali on 13/10/2015 16:06:58:

Truth be told, I feel a bit miffed at loosing sales resulting from others wide spread industry practice of marketing input power figures to promote their machines.

Ketan at ARC.

If you don't want to lose sales why do you cancel some orders with card payments? I had an order cancelled but I didn't realize it had been cancelled for over a week as the email was in my junk folder. Something to do with me paying with my PayPal Access card? I've never had this problem anywhere else.

I have just got the money back over a month after I ordered, despite being told the money wouldn't be taken out in the first place

[Ketan SwaliParticipant @ketanswali79440]

Hello Chris,

I am sorry you feel unhappy about our policy with reference to PayPal as a service provider. To the best of my knowledge this is stated on our website before a buyer proceeds to the payment screen. Unfortunately at present PayPal fails to provide adequate payment guarantees with security to meet the comfort we need. This matter has been covered elsewhere. This may be acceptable to other sellers, but anything connected to PayPal directly or indirectly is outside the scope of acceptance to ARC for the time being.

When you place your order though our website, we only take an authorisation to take the funds allocated to an order. We never take the payment. It is a kind of 'shadow/block' against the funds. If we are happy to process the order after making relevant checks, we release the 'shadow/block' and take the payment. Otherwise, we abort the authorisation.

How long your service provider takes to release the blocked funds to you is something you need to discuss with them. According to International Banking practice, there should not be such a delay. However, PayPal is outside the U.K., and how they or their connected partners wish to behave is something that you may wish to take up with them. We generally release or abort the authorisation within 24 to 48 hours of an order being placed, or at the time of processing a large order for a lathe or mill. If an order is aborted, we advise you immediately. It is unfortunate that some emails end up in junk mail, for which I can only apologise. If you send an email to me, I will be happy to provide you proof that we did not take your money, which in turn you can present to your payment service provider for them to explain to you why it took them over a month to return the payment back to you.

Please accept my apologies for failing to meet your expectations.

Ketan at ARC.

[Chris DentonParticipant @chrisdenton53037]

Posted by Ketan Swali on 18/10/2015 12:09:43:

Hello Chris,

I am sorry you feel unhappy about our policy with reference to PayPal as a service provider. To the best of my knowledge this is stated on our website before a buyer proceeds to the payment screen. Unfortunately at present PayPal fails to provide adequate payment guarantees with security to meet the comfort we need. This matter has been covered elsewhere. This may be acceptable to other sellers, but anything connected to PayPal directly or indirectly is outside the scope of acceptance to ARC for the time being.

When you place your order though our website, we only take an authorisation to take the funds allocated to an order. We never take the payment. It is a kind of 'shadow/block' against the funds. If we are happy to process the order after making relevant checks, we release the 'shadow/block' and take the payment. Otherwise, we abort the authorisation.

How long your service provider takes to release the blocked funds to you is something you need to discuss with them. According to International Banking practice, there should not be such a delay. However, PayPal is outside the U.K., and how they or their connected partners wish to behave is something that you may wish to take up with them. We generally release or abort the authorisation within 24 to 48 hours of an order being placed, or at the time of processing a large order for a lathe or mill. If an order is aborted, we advise you immediately. It is unfortunate that some emails end up in junk mail, for which I can only apologise. If you send an email to me, I will be happy to provide you proof that we did not take your money, which in turn you can present to your payment service provider for them to explain to you why it took them over a month to return the payment back to you.

Please accept my apologies for failing to meet your expectations.

Ketan at ARC.

The email said "Please note no money has been taken." (copy and paste has changed the font size)

But the money had been taken from my account as a result of a purchase from you

You need to make it more obvious on your website that PayPal Access cards cannot be used without losing the money for a month or finding a way to stop them being used on your website altogether.

[AjohnwParticipant @ajohnw51620]

That might be Paypal Chris and probably is.

I had a problem with Arc too some time ago with a Lloyds debit card. They had changed the way the transfer was handled – effectively delayed from what I could find out about it.

This was rather a long time ago.

John

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[Ketan SwaliParticipant @ketanswali79440]

Chris,

I can guarantee that we did not take your money, and I can prove it. If money was taken, it was taken by PayPal to issue a block/authorisation. So on this point, I respectfully disagree with you.

We have clearly stated that we do not accept PayPal. What is obvious or otherwise is open to debate. I would assume that by saying we do not accept PayPal that it is obvious that we do not accept anything related to it – cards or otherwise. But I guess that we will have to add more comments such as PayPal or any cards or forms of payment associated with it or virtual cards are not accepted. We will consider this when we review our site, but I fail to understand why ARC should have to answer for PayPal taking your money and holding your funds for so long. I believe that is wrong, and it is an issue between you and PayPal.

As mentioned before, I am happy to provide you evidence that ARC has not taken your money if you send me an email. Although I would like to post the proof here, it would be inappropriate to disclose such information on an open forum.

This thread covers motor input and output power. I believe that I have answered your questions which are off topic. Could I please request that we stay on topic?

Ketan at ARC.

[Robin GrahamParticipant @robingraham42208]

To return to the original (interesting if confusing topic), Ketan said:

'As a marketing tool, well known badged brands as well us unknowns piggybacking, are choosing to quote input power – as it is obviously higher, but when challanged, still say it is output power. Apparently this is acceptable too, because it has something to do with temperature and peak over time !?!. This went a little above my head, as I am a commercail person, but again, how can this be correct ?.

In other words, how can someone say that they have a 1,100W brushed motor, when what they really mean is that it is about 700W motor output, and still be correct in saying it is a 1,100W motor. How cn this be right?'

I wonder if this is a bit like the 'Peak Music Power Output' vs RMS thing you get with audio amplifiers. I don't know about the brushed motors under discussion, but induction motors can produce up to twice their rated continuous power output at the shaft (Jim Cox WPS 24) as they approach stalling torque. Of course they wouldn't last long if run like that continuously – they would overheat. He points out that this can be exploited in a home workshop environment, where motors are rarely run continuously, by using 'underpowered' (and hence cheaper) motors.

If something similar is true of brushed motors, maybe this is what SEIG are getting at – a motor rated for 700W continuous output might be capable of 1100W for the short bursts typical of home use, because it gets 'cooling off time', so as it's being sold as a hobby machine maybe it's OK to market it as 1100W?

As far as ARC's marketing goes, I'd much sooner buy a machine with a clearly stated motor power (ie continuous power at the shaft) than one that just quoted something vague and ill-defined, just as I'd sooner buy an audio amp with a clearly stated RMS output. I may be atypical tho. When I was in the market for my first lathe, if I'd gone for a Chinese import it would have been from ARC precisely because the marketing admitted that the machines might need a bit of fettling (which research had told me anyway) and ARC were offering to do that at a reasonable fee. I recall that when that service was withdrawn Ketan posted on this site to explain that potential customers were put off because there was a perception that the preparation service was only necessary because the ARC offerings were in some way inferior to the competition, which wasn't true.

Must sometimes be hard to square personal principles with commercial realities!

Robin.

[egaParticipant @ega]

john fletcher 1:

"Yes, the inverter can be plugged into the power meter"

Thank you for answering my question

[Author]

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