Current, wattage, HP and 3 Ph motors

[simonl]

Hello all,

I have a 3 phase variable speed (frequency) motor that I have waiting for a project. Question is, to work out the wattage of the motor is it the same as for a single phase electric motor as in Volts x Amps = Watts, then divide by 746 for horsepower?

The spec plate says it draws 6 amps, so does that mean about 1400 watts and just shy of 2 HP?

Cheers,

Simon

[.RC.]

6 amps per phase?

[simonl]

6 amps per phase?

Dunno. It was off a treadmill which had a standard 10 amp plug so I can't see it being anymore than 10 amps total either way. Probably less.

Simon

[Ueee]

Hi,
Your voltage should be 440 so 6 amp would be 2640w.......
Ewan

[Ueee]

But after your last reply thats more than 10 amp.....

[simonl]

Hi,
Your voltage should be 440 so 6 amp would be 2640w.......
Ewan

No, it's 240 V 3 Ph.

Cheers,

Simon

[NCArcher]

What else does the spec plate say? Treadmill motors are often non standard with a special VSD to control them. My treadmill motor is 2HP but it is 240V DC I think.

Edit: too slow

[simonl]

The only reason the motor is 3 Ph is because they use a dedicated VFD to vary the speed of the treadmill. Some treadmills use a DC motor and vary the duty cycle by PWM but this one uses a 240 V 3 Ph motor and a VFD.

Cheers,

Simon

[NCArcher]

I make it 3HP.
E x I x root3 x power factor

[RayG]

Dunno. It was off a treadmill which had a standard 10 amp plug so I can't see it being anymore than 10 amps total either way. Probably less.

Simon

Are you sure it's a three phase induction motor, it's not brushless DC by any chance?

I can't see a treadmill having a 415 V 3 phase induction motor, but who knows?

There should be a name plate, if not some other identification.

Regards
Ray

PS... Seems like there were 3 or 4 posts while I was typing, 240 x 6 x 1.732 x 0.85 = 2.2 kw 3 hp it is..

[Ueee]

I would say your 2hp would be right then.
Never thought of treadmill motors as good speed controlled motors. Oh dear something else to look out for. Mind you, DC would be great with PWM (now you speakin my language) and feed back as you can still get close to full power at low revs.
Ewan

[Tools4Me]

Hello all,

I have a 3 phase variable speed (frequency) motor that I have waiting for a project. Question is, to work out the wattage of the motor is it the same as for a single phase electric motor as in Volts x Amps = Watts, then divide by 746 for horsepower?

The spec plate says it draws 6 amps, so does that mean about 1400 watts and just shy of 2 HP?

Cheers,

Simon

Simon, what you need is this formula: P(W) = √3 × PF × I(A)× V(V)

Your fully loaded 6A motor will have a power factor of about 0.8PF on our 415V 3 phase mains. √3 is about 1.73 or thereabouts.

So that's about 3,400W or 4.6Hp in the old money.

[jack620]

Something's not right here. 3400W is a HUGE amount of power for a treadmill. In any case, you wouldn't be able to plug it into a 10A GPO if it drew 3400W.

I also tend to think it might be a brushless DC motor.

[Ueee]

Something's not right here. 3400W is a HUGE amount of power for a treadmill. In any case, you wouldn't be able to plug it into a 10A GPO if it drew 3400W.

Tools4me assumed like i did, that is 415v, but its only 240, so if you pop that into the calculations you get 1992w, but i'm not sure if the PF would be the same.

Hmmm i think the only sure thing is that you have a motor.

You don't have one of those power meters that you plug in do you? you could plug it into one and run it on full to see what the draw is.

Ewan

[Ueee]

Simon, what you need is this formula: P(W) = √3 × PF × I(A)× V(V)

Your fully loaded 6A motor will have a power factor of about 0.8PF on our 415V 3 phase mains. √3 is about 1.73 or thereabouts.

So that's about 3,400W or 4.6Hp in the old money.

Tools4me,
Am i right in thinking that to work out any 3 phase wattage you use the square root of the no of phases? So it a motor is running on, oh god brain failure, delta? only, you would use the square root of 2 (i think i'm right in thinking that a motor in delta only uses 2 phases, star is 1 and star/delta is all three)? I know plenty about DC and single phase, but three phase is, well, 3 times as complicated.

Ewan

[RayG]

Hi Ewan,

Well, power is ALWAYS volts times amps, the complication is that , first the current lags the voltage, and that phase shift is represented by the power factor, if it was a purely resistive load the current and voltage would be in phase, second the voltage applied to the coils is the voltage between the phases, so for 415 3 phase, the voltage between any phase (and neutral) is 240V... confused yet.. 240 times 1.732 = 415

Regards
Ray

[Ueee]

Hi Ewan,

Well, power is ALWAYS volts times amps, the complication is that , first the current lags the voltage, and that phase shift is represented by the power factor, if it was a purely resistive load the current and voltage would be in phase, second the voltage applied to the coils is the voltage between the phases, so for 415 3 phase, the voltage between any two phases is 240V... confused yet.. 240 times 1.732 = 415

Regards
Ray

Hence the 415v! (a genuine light bulb moment that one...) I know you can take any one of the phases and get 240 single phase, and understand that a motors load is not like a single resistive coil, but still don't get how a motor can run on 2 phases only.....

I worked for an Electrician when i was 15 or so, but we mostly did remote solar installs, nothing big, so i didn't know 3 phase existed till i moved to the city and got my apprenticeship at 16.

Ewan

[simonl]

Hello all,

Keep coming with the replies. I learning lots, mainly learning just how little I know!

The motor is definately a 240V 3 phase induction motor. It's from a Lifefitness 9000 treadmill. They use a dedicated motor and controller made my Emerson. I will take a photo of the motor tomorrow when I get home from work. For anyone interested, here is a link to the service manual of the treadmill, it contains an electrical shematic on page 55. http://www.sportsmith.net/images/product_support%5Clifefitness%5CTreadmills%5CTr9000%5C9000%20Treadmill%20Manuals%5CService%5Cm05100k45a012%209000%20Treadmill%20Svc%20Manual.pdf

It is important to note that the treadmill does not actually exist anymore, only the motor and the control board. So it's not working (it was working before I took it apart!) as I need to add an imput signal into the control board. Well, at least that's my theory!

Cheers,

Simon

[eskimo]

Well, power is ALWAYS volts times amps, the complication is that , first the current lags the voltage, and that phase shift is represented by the power factor, if it was a purely resistive load the current and voltage would be in phase, second the voltage applied to the coils is the voltage between the phases, so for 415 3 phase, the voltage between any phase (and neutral) is 240V... confused yet.. 240 times 1.732 = 415



thats why I take my motors to the rewind shop if they dont work....bloody too complicated for me...I must have been asleep when they tried to teach me that stuff at tradeschool:D

[eskimo]

. So it's not working (it was working before I took it apart!) as I need to add an imput signal into the control board. Well, at least that's my theory!

Cheers,

Simon

looking at the wiring diag you may well be right

cant fathom why they have two feeds coming from the trany but?...why not just take the 240v straight to the VSD/VFD?...all the trany does is reduce the voltage to 120 for the main control board

[Ueee]

looking at the wiring diag you may well be right

cant fathom why they have two feeds coming from the trany but?...why not just take the 240v straight to the VSD/VFD?...all the trany does is reduce the voltage to 120 for the main control board

Its an American product so the systems are designed to run on 120v, hence the tranny.
The controller probably uses a PIC or ATMEGA so it and the display will run on 5v dc (via switchmode driver on the controller board)

You will need all the bits to make the motor work probably, the VFD will be made specially for the treadmill.

Ewan

[morrisman]

HI

I did basic electronics course years ago ..forgotten most of it

I remember RMS values though. RMS = root mean square . e.g., the 240 v single phase actually has a peak of around 340V . THE 240 V is the RMS value , it's not an average value , but it's the value that equates to a DC circuit . RMS means we can use OHMS law to work out amps , power etc etc.

Power factor relates to the reactive component of the load , either inductive or capacity . Big factories used to have big caps on their system to nullify the inductive loads of motors etc. lower PF is the goal .

Can somebody explain how 3 phase is available from 2 wires ? The normal power grid ( like is used here ) has 2 wires ..how do they get 3 phases from 2 wires ?

MIKE

[eskimo]

Its an American product so the systems are designed to run on 120v, hence the tranny.
The controller probably uses a PIC or ATMEGA so it and the display will run on 5v dc (via switchmode driver on the controller board)

You will need all the bits to make the motor work probably, the VFD will be made specially for the treadmill.

Ewan

yeah I know it was designed to run on 120v and the trany is there for that...but why two (2) x 220v feeds to the VSD?...they both come from the 220V secondary of the tranny...maybe the VSD wants 220...but if so why is it so critical...why cant it run on 240?

[Stustoys]

cant fathom why they have two feeds coming from the trany but?
I wonder if its just to keep the current down?


why not just take the 240v straight to the VSD/VFD?
My first thought was isolation, but autotransformers dont do that.


all the trany does is reduce the voltage to 120 for the main control board
And 221V for the motor.

Stuart

Thanks for the edit Ray, I'd been scratching my head half the night over that one lol

[eskimo]

and the motor is 240v...so Simon says

I wouldnt have thought that the VSD was demanding it required 220v...normally they are very tolerant of a wide voltage range

[simonl]

Hi all,

Thanks for the input so far. Here is a pic of the motor as promised. Have a look and tell me how many horses are inside it!

Also, what does SFA stand for. I know SFA about it and I'm sure it doesn't mean that! Assume it's to do with power factor, it's not that important to me but since I've got the brains trust looking at it I may as well ask as many questions as I can!

Cheers,

Simon

[NCArcher]

SFA is an American thing. It stands for Service Factor Amps. You'll note that there is a SF rating of 1. on the line above.
It is part of the US electrical code and has to do with the thermal protection applied and the expected life of the motor.
Oh and it's 3 HP

As for the two 221V supplies to the VSD, I think you'll find that is a standard loom configuration so that they can manufacture one loom and apply it to many different models. Other models may have multiple VSDs or some other component connected to that same plug.
The VSD will probably work on a wide range of voltages but the control board needs 120V.
And Morrisman, the VSD takes a single phase supply and reproduces it twice offsetting the wave form by 120° each time to give you 3 phases. A bit simplistic but basically what happens :shrug:

[Stustoys]

I wouldnt have thought that the VSD was demanding it required 220v...normally they are very tolerant of a wide voltage range
Good point. But the controller on the 240V wiring diagram is labeled 120V. So maybe they use the same VSD and 220V was as high as they could take it without changing components?

*edit* but that would mean it was way over built for 120V??? Who knows what they were thinking lol

Stuart

[Ueee]

SFA is an American thing. It stands for Service Factor Amps. You'll note that there is a SF rating of 1. on the line above.
It is part of the US electrical code and has to do with the thermal protection applied and the expected life of the motor.
Oh and it's 3 HP

Hi,
Can you give us the formula you used to get to 3 hp?
Ewan

[NCArcher]

I make it 3HP.
E x I x root3 x power factor


...

PS... Seems like there were 3 or 4 posts while I was typing, 240 x 6 x 1.732 x 0.85 = 2.2 kw 3 hp it is..


Simon, what you need is this formula: P(W) = √3 × PF × I(A)× V(V)

I think T4Me put it best. I could not find the sq. root symbol (still can't)

[simonl]

Hello all,

Thankyou to everyone who helped shed light on this project waiting to happen!

Being 3 HP certainly allows for some scope with deciding what use to put it to, assuming I can trick the controller into making it work!

Variable speed for my mill is probably at the top of the list of projects for this motor but it will be a long way off. It will sit in my cupboard until I'm ready!

Now, getting back to "tricking the controller", Looking at the controller board you can see that the controller board has inputs. These inputs would normally come from the treadmill control panel where the user would select such conditions as speed, incline etc etc.

The seven inputs into the speed controller are:

1 : GND (no surprises here)
2 : Key (but not physically used or connected)
3 : Enable/Disable (maybe linked to the emergency stop etc)
4 : Speed Count (Assume this sets the speed of the motor. I'm thinking of a square wave input of varying frequency of say 1 - 10 Khz but would have to plug to function generator with a TTL output to verify)
5 : Efast/Slow (Speed of motor maybe set in two parts depending if this pin is hi or low)
6 : Emotor on (Not sure, maybe some feedback circuit)
7 : Ematch (Not sure but it may be a variation of vector control to make sure that the motor maintains the selected speed regardless of how fat/heavy the person is)

Another assumption I have is that all these inputs are digital inputs since they all pass through an optocoupler on the controller board immediately after the data connection.

Based on my assumptions, I'm thinking that I should only need to determine the correct frequency range for pin 4 and then work out whether the other pins are active hi or low..

If I can crack it, then I think it will make a cracking motor and VFD combo for free!

Also id I make a dedicated PIC program and circuit, I could use the input signal on pin 4 to make a dedicated tacho display for it.

Just my ideas on this.....

Cheers,

Simon

[simonl]

i think t4me put it best. I could not find the sq. Root symbol (still can't)

thankyou!

[RayG]

Hi Simon,

On that CCT it appears to show a lubrication pump? If it's any good that's a handy little bonus. :)

Regards
Ray

[simonl]

Hi Simon,

On that CCT it appears to show a lubrication pump? If it's any good that's a handy little bonus. :)

Regards
Ray


Hi Ray,

yes I have kept all that, including the motor that raises and lowers the treadmill.

The pump is driven by a small 110V induction motor so I have kept the pump and the transformer that drives it. Was thinking of using the pump to set up a one shot lubrication system and have it plumbed to both the lathe and mill. Just open the valve and run the pump for a few seconds..... something like that anyway.

The actual pump is interesting, it's contained in a small plastic case and contains an arm with two rollers that rotates on a shaft. Inside is a flexible tube that the lubricant flows through and as the rollers move around, it squeezes the tube and forces the lubricant through. Very simple design.

Cheers,

Simon

[malb]

In the service manual linked, page 50 has the parts list. The first item is Drive Motor 2HP, so I suspect that the unit is actually 2HP rather than 3HP.

Rather a mute point anyway. Electric motors will draw as much current as they need to to handle an imposed load. The power rating is a measure of how much power can be drawn without overheating the motor. Slow the motor, and you slow the fan and reduce cooling flow and hence lower the power rating of the motor unless you have auxiliary cooling fans etc.

[simonl]

In the service manual linked, page 50 has the parts list. The first item is Drive Motor 2HP, so I suspect that the unit is actually 2HP rather than 3HP.

Rather a mute point anyway. Electric motors will draw as much current as they need to to handle an imposed load. The power rating is a measure of how much power can be drawn without overheating the motor. Slow the motor, and you slow the fan and reduce cooling flow and hence lower the power rating of the motor unless you have auxiliary cooling fans etc.

Perhaps the motor is rated to 3 HP but the control board, due to maximum speed restriction of the treadmill will only allow a max. of 2 HP?

So, my mill has come standard with a 2 HP motor. Are you suggesting that I can replace that with a 1 HP, 2 HP or 3 HP variable speed motor and it won't make any difference?

Also, I assume if you slow the motor and slow the cooling fan, then you reduce the power going into it anyway. Isn't that the point?

Simon

[eskimo]

Electric motors will draw as much current as they need to to handle an imposed load.

That assumes that the motor is capable of handling the imposed load.

no Simon
if you have a load that requires 3hp you must have a motor that can handle that load...A 1 or 2 hp wont do
putting a 3hp motor on a 1hp load will work...its just inefficient and higher upfront cost...but if you get the motor for zilch then its just inefficient

and your treadmill motor is specifically manufactured for frequency driving(refer motor ID plate) ..most standard motors are not designed for frequency driving much above 60HZ..they work above this but are not manufactured for it

A 400hz VSD/VFD could theoreticaly drive a standard 1440rpm motor to 12000rpm ....(this is synchronous speed)...but the motor would be destroyed if one tried
motors for high frequency input are purpose built.

[Graziano]

How many wires go into the motor, does it have any brushes?. Nearly all treadmill motors I've seen are variable speed 2Hp DC controlled by PWM speed controllers.

[Stustoys]

Hi guys,

How many wires go into the motor
According to the wiring diagram 5 wires. Ground, two for a thrm cut out and three labled phase 1, phase 2 and phase 3. The motor has PH. 3 on the label.

Eskimo, I nearly got to see what a 3hp motor looked like at 12000rpm. The manual for my VSDs says the factory setting is 50Hz, it wasnt. Luckily the ramp was set at around 25 seconds. :rolleyes:

Stuart

[Graziano]

Hi guys,

According to the wiring diagram 5 wires. Ground, two for a thrm cut out and three labled phase 1, phase 2 and phase 3. The motor has PH. 3 on the label.

Eskimo, I nearly got to see what a 3hp motor looked like at 12000rpm. The manual for my VSDs says the factory setting is 50Hz, it wasnt. Luckily the ramp was set at around 25 seconds. :rolleyes:

Stuart

Ahhh RTFM!:doh: I'm gonna plead "Lack of caffeine"

[simonl]

Hi guys,

Eskimo, I nearly got to see what a 3hp motor looked like at 12000rpm. The manual for my VSDs says the factory setting is 50Hz, it wasnt. Luckily the ramp was set at around 25 seconds. :rolleyes:

Stuart

Hi Stuart,

What would have happened if you let it go? Can a VSD drive a motor to such hi RPM'S? If so, would it just be a matter of the bearings failing after they reach their limits?


Also, Malb's point has me thinking. When you vary the speed of a 3 ph induction motor via a VSD or VFD, are you actually varying the HP output of the motor as well?

Will a 2 HP motor produce and draw the same current at 500 RPM as it would when it's dialled up to run at 1000 RPM? Is it putting out 2 HP and both speeds?

Now throw in Vectoring, which I assume contains a feedback circuit to ensure the motor speed remains constant regardless of the load which it is under. Does this then change things or does a 2 HP motor always draw 1500 Watts (during running, not start up) regardless of its speed?

I hope I have worded the question properly....

Cheers,

Simon

[tinkera]

Hi simonl,
The pump you describe is a peristaltic pump, Wikepedia have a good description.
tinkera

[simonl]

Hi simonl,
The pump you describe is a peristaltic pump, Wikepedia have a good description.
tinkera

Hi Tinkera,

You are correct, in fact the picture looks almost identical to the one I have. Glad my more than woeful description at least made some sense! Thanks for the info.

Just in case anyone else is interested here is the link to the Wiki article.
http://upload.wikimedia.org/wikipedia/commons/0/04/Peristaltic_pump_head.jpg

What makes this pump perfect for lubrication is firstly it's relatively low output as about what you would need for a lubrication system. Secondly, being a positive displacement pump, you can have the coolant lower than the pump and still not have to worry about priming the pump if air bubbles get into the system since positive displacement pumps will pump gas as well as air. Unlike centrifugal pumps that will only pump fluids.

Cheers,

Simon

Cheers,

Simon

[malb]

That assumes that the motor is capable of handling the imposed load.


Actually it doesn't make that assumption at all. It's a simple fact that if the motor cannot handle the imposed load, it either trips it's own protection, a fuse or breaker in the supply network, or destroys itself.

The point I was making is that the manufacturers power rating is an indication of the amount of heat that the motor can disipate without damage, not the hard limited input power consumption.

[RayG]

Actually it doesn't make that assumption at all. It's a simple fact that if the motor cannot handle the imposed load, it either trips it's own protection, a fuse or breaker in the supply network, or destroys itself.

The point I was making is that the manufacturers power rating is an indication of the amount of heat that the motor can disipate without damage, not the hard limited input power consumption.

Hmmm... you are assuming the stall current will destroy the motor... What about stepper motors, brushless DC, shaded pole motors etc etc...

The manufacturers power rating is a function of many factors, how the motor is wound, number of turns per lap, wire gauge used, number of poles, how efficiently the magnetic flux is transferred to the rotor and so on... You can't expect to get 10 hp out of a 3 hp motor just by loading it... As you increase the load beyond the torque that the motor is capable of, the motor slows down and the hp ( the work done the motor) decreases linearly with rpm.

hp= torque*rpm / 5252

Lower rpm = lower hp

Regards
Ray

[Stustoys]

Hi Simon,
I'm not sure what would happen. I think the bearings would be fine in the short term. It would likely go past 2800rpm, then either get to a point that the motor couldnt speed up (due to some eletrical effect that I wouldnt fully understand even if I knew what it was, say saturation of the laminations or eddy currents) or the rotor would come to pieces.

Yes Hp goes down with rpm. The best you can hope for is the same torque(or maybe a little more). I have no idea what happens to Hp when you go over the motors rated rpm. My guess is you could get more power, but more power would be more heat.

Dont have a vector drive, I believe the do a better job of maintaining rpm. A normal VSD is just guessing.


A 2hp motor doesnt always draw 1500W, it only draws 1500W when you're asking it to do something that takes 2hp, what it draws at "idle" I have no idea.

Hope I've covered your questions(and someone fixes my misstakes)

Stuart

[malb]

Hmmm... you are assuming the stall current will destroy the motor... What about stepper motors, brushless DC, shaded pole motors etc etc.

Stall of any induction motor will eliminate generation of back EMF and allow excessive current draw unless externally limited. That's why single phase motors get unhappy quickly if the start winding. cap, switching system fail.

I have come accross Steppers and Brushless DC connected to mismatched controllers that have burnt out due to being overloaded, If the contoller does not limit power to safe limits, the motor will not do it intrinsicly and can be damaged by overload.. Haven't had enough to do with shaded poles to comment.

The manufacturers power rating is a function of many factors, how the motor is wound, number of turns per lap, wire gauge used, number of poles, how efficiently the magnetic flux is transferred to the rotor and so on...

With the exception of Flux transfer, the factors that you mention are optimised to minimise heat generation and thermal losses, which is the point I am making. i.e it is easier to get current flowing in a motor than it is to disipate the heat generated by associated losses. Go into overload and it is the thermal performance that counts.

You can't expect to get 10 hp out of a 3 hp motor just by loading it.

I never suggested that you could. The point I was trying to make to the OP was that motor would attempt to meet the demands placed upon it by the load, rather than conduct a fixed current to generate a fixed power. Provided that the demands to be met were lower than rated power the unit would safely supply them, If they exceed rated power, the motors thermal performance is the critical issue unless significant external control is employed.

As you increase the load beyond the torque that the motor is capable of, the motor slows down and the hp ( the work done the motor) decreases linearly with rpm.

The motor produce zero net power (and Torque) at no load, It is merely overcoming it's own mechanical and electrical losses, which may be up to 35% of it's rated input power. As you apply a load, the motor generates torque in order to drive the load, and the motor increases it's power consumption. In an induction motor, the motor will slow below synchronous speed (slip). Torque generation and power consumption increases with slip, and there is no magic stopping point when the motor reaches it's rated output. If allowed to continue in overload, the motor will fail due to overheating unless protected by an intergated thermal protection device, external contols or supply network fuses or breakers.

The motor is effectively a torque on demand device. The torque can increase almost infinitely from the no load situation, or by a factor of maybe 500% in a situation where the motor belt drives a load, while the RPM of the motor drops by typically less than 10%.

hp= torque*rpm / 5252

Therefore your assumption below does not hold in relation to an induction motor being slowed by application of a load as variation in torque will be greater than variation (in opposite direction) of RPM.

Lower rpm = lower hp

Regards
Ray


Mal

[RayG]

I have no idea what happens to Hp when you go over the motors rated rpm. My guess is you could get more power, but more power would be more heat.


Hi Stuart,

When you go over the rated 50Hz, the power stays constant for a while, but eventually slippage will limit the maximum rpm....

EDIT .. It goes without saying that since HP stays the same while rpm is increasing, the torque starts decreasing above 50 Hz.

This is for a V/F drive
http://www.backsaw.net/pics/Misc/MotorBasics.jpg

Not sure what happens to the bearings as you get to higher rpm, fan cooling should be better however... :rolleyes:

Malb,
Ignore the above graph, it's relevant to V/F drives, not what we were discussing.

I think we are converging on much the same viewpoint, I could take issue with the infinite torque comment, but either way, the end result is the same... if you overload a motor it slows down, eventually stalls and if not protected burns out by overheating... I hope we can agree at least on that. :)

Regards
Ray

[eskimo]

Actually it doesn't make that assumption at all. It's a simple fact that if the motor cannot handle the imposed load, it either trips it's own protection, a fuse or breaker in the supply network, or destroys itself.

The point I was making is that the manufacturers power rating is an indication of the amount of heat that the motor can disipate without damage, not the hard limited input power consumption.

Not every one understands or know those simple facts
your wording "Electric motors will draw as much current as they need to to handle an imposed load." gives or may give to those who do not know and could make them assume that a 1hp could draw as much current as it want...with out detrimental effects...hence my words.

no that its all cleared up I hope Simon understands

[simonl]

Not every one understands or know those simple facts
your wording "Electric motors will draw as much current as they need to to handle an imposed load." gives or may give to those who do not know and could make them assume that a 1hp could draw as much current as it want...with out detrimental effects...hence my words.

no that its all cleared up I hope Simon understands

Thanks Eskimo and everyone else, I have been taking in as much of this info as possible. I have been interested about variable frequency drives and motors since I have never played with one yet. Like I said earlier, I have this motor and controller but I wanted to know what it's capabilities are in terms of its power. I guess simplistically I assumed that if I want to replace the factory 1500 W induction motor with a variable frequency drive motor, then it needed to be a similar power otherwise a reduction would be a compromise. I guess to make my point, I think I would be disappointed if I replaced the motor with a 200 Watt 3 ph motor and speed controller and expected to perform similar to the factory 1500W motor. Conversely, putting in a 2400W motor would most likely be unnecessary.... unless it was a freebie that is!

Hope I made sense.

Keep talking everyone, I'm listening!

[RayG]

Hi Simon,

I wouldn't be surprised if that Emerson drive and motor, were a little more sophisicated than we have been thinking. They make pretty good stuff, I've never programmed them, but I've seen Emerson drives used in some pretty slick applications.

I wonder if that controller is a vector drive? It would be the sort of characteristic that would suit a treadmill application....

If it is you will get full torque across the speed range, that's a handy feature to have.

Regards
Ray

[simonl]

Hi Simon,

I wouldn't be surprised if that Emerson drive and motor, were a little more sophisicated than we have been thinking. They make pretty good stuff, I've never programmed them, but I've seen Emerson drives used in some pretty slick applications.

I wonder if that controller is a vector drive? It would be the sort of characteristic that would suit a treadmill application....

If it is you will get full torque across the speed range, that's a handy feature to have.

Regards
Ray

I think you may well be correct Ray. I reckon I'll have a read hot go at getting it working for me! Like I said, those inputs seem to be digital to me. Just have to come up with the correct sequence to fool the system.

The first thing I'm going to have to come up with is a simple PIC program to produce a TTL square wave output on my prototype board. That won't take long along with a simple program code.

I'm spewing I didn't take some measurements before I actually dismantled the thing! But I didn't realise what I had when I took it apart. I was quite disappointed when I saw it wasn't a DC motor so assumed it was no good to me. Was only after reading about VFD's on this forum that it clicked about what I had, by that time the treadmill was already out in the backyard for about 12 months! Everything still powers up OK, it's so well made that even out in the weather, the vital components were protected.

Cheers,

Simon

[Ueee]

The first thing I'm going to have to come up with is a simple PIC program to produce a TTL square wave output on my prototype board. That won't take long along with a simple program code.



Off topic again, but is there any particular reason you use PIC over ATMEGA? I like my Arduino's, they are great fun to play with.

Don't you have the original control board from the treadmill? I'm guessing not cause that would be the easiest way to test the motor.

Ewan

[RayG]

Off topic again, but is there any particular reason you use PIC over ATMEGA? I like my Arduino's, they are great fun to play with.

Don't you have the original control board from the treadmill? I'm guessing not cause that would be the easiest way to test the motor.

Ewan

Hi Ewan,

Real programmers use PIC, Arduino's are toys**... :D

Actually Microchip has lately been pushing it's Arduino clone system, in view of the popularity of the Arduino..

For what it's worth I use both, but prefer Hi-Tech C on the pics, but programmed pics in assembler for many years..

Regards
Ray

**Just kidding... actually I don't mind Arduino, I wonder if there is an "Emerson Shield"...

[simonl]

Off topic again, but is there any particular reason you use PIC over ATMEGA? I like my Arduino's, they are great fun to play with.

Don't you have the original control board from the treadmill? I'm guessing not cause that would be the easiest way to test the motor.

Ewan

Hi Ueee,

Don't want to bore you too much but I found the treadmills (yes 2) when I drove past a local gym, they were throwing them out and had them out in the carpark where they stayed for a few days. After asking permission I decided to take them home thinking there must be some good parts in them, a DC motor being one part I wanted.

Out of interest, after lugging them home I plugged them in and they both worked fine although they looked very used and the hour meter showed many thousands of hours (meant nothing to me). So, I figured I may as well take one apart and have a look. To my surprise, no DC motor but an AC one. I figured I couldn't really use an AC motor (not for a wind generator anyway which is what I had in mind) So I looked at both and decided to make one good one out of the two that would look OK. I then sold the good one on ebay and made a tidy profit which left the other and home, where it sat in the backyard for a while. It sat there until I realised that I had a 3 ph motor with a VFD, after reading and lurking on this forum. By this time I had already thrown out the top console - Bad mistake! Very bad mistake :C

So i wasted no time in recovering all the good stuff, including the pump, motor and controller.

Why use PIC? Well actually I use PICAXE stuff because I have never bothered to learn assembly and PICAXE stuff (as you probably know) has a bootleg program inserted that makes the programming an easier process. You no doubt do loose some flexibility with it but for me it's fine. I learnt about these after reading about them in SC magazine and I just kept using them since as that is what I have become used to.

I really should learn PIC programming and buy a PIC programming board.

Cheers,

Simon