AC motors

[Anonymous]

i stand corrected...thats what i get for answering questions when im half asleep...99% of my experience was in 3 phase repair and that is what my answer was based on but FLEE pointed out my error...sorry for the bogus answer i see there are several people that have more elec. engineering knowledge than me and i will leave this to them.....scott

[Anonymous]

i stand corrected...thats what i get for answering questions when im half asleep...99% of my experience was in 3 phase repair and that is what my answer was based on but FLEE pointed out my error...sorry for the bogus answer i see there are several people that have more elec. engineering knowledge than me and i will leave this to them.....scott

[Anonymous]

It is true, AC motors run at essentially one speed, determined by the number of electrical poles ususally on the stator, but this is true only for three phase synchronous motors. Straight poly phase induction motor's rpm will vary as the load is increased, difference in RPM called "slip". A commercial DC motor's speed is varied by changing the armature (ususally the rotating part) current, i.e., the magnetic field. Any wave form other than DC (none) is AC, even a lighting strike (fast time rise). AC locomotives generate AC which is rectified to DC and then "reconverted" to AC usually using a PWM (pulse width modulating) system quit similar to DCC systems. The motor RPM is controlled by the width (therefore the number of "pulses/second) of the pulses. The "frequency" of the number of cycles creates the singing noise heard in the earlier DCC systems. To be authentic, you'd need three phase on your "track" to use a straight AC motor (or a convertor in the loco).

[Anonymous]

It is true, AC motors run at essentially one speed, determined by the number of electrical poles ususally on the stator, but this is true only for three phase synchronous motors. Straight poly phase induction motor's rpm will vary as the load is increased, difference in RPM called "slip". A commercial DC motor's speed is varied by changing the armature (ususally the rotating part) current, i.e., the magnetic field. Any wave form other than DC (none) is AC, even a lighting strike (fast time rise). AC locomotives generate AC which is rectified to DC and then "reconverted" to AC usually using a PWM (pulse width modulating) system quit similar to DCC systems. The motor RPM is controlled by the width (therefore the number of "pulses/second) of the pulses. The "frequency" of the number of cycles creates the singing noise heard in the earlier DCC systems. To be authentic, you'd need three phase on your "track" to use a straight AC motor (or a convertor in the loco).

[Anonymous]

Well, I know of a few suppliers in the UK, but I'm not sure if they'll ship to the States. there's a supplier named Branchlines (email [e-mail]), who also offer the Black Beetle units which are very similar (these offer different wheelbases/wheel sizes to the SPUDs). There's also www.dckits.co.uk (Their main speciality is plastic kits for multiple units, but they also sell SPUDs/Black Beetles). I'd advise trying the latter first as they have a website - Branchlines only appear to have an email address!

[Anonymous]

Well, I know of a few suppliers in the UK, but I'm not sure if they'll ship to the States. there's a supplier named Branchlines (email [e-mail]), who also offer the Black Beetle units which are very similar (these offer different wheelbases/wheel sizes to the SPUDs). There's also www.dckits.co.uk (Their main speciality is plastic kits for multiple units, but they also sell SPUDs/Black Beetles). I'd advise trying the latter first as they have a website - Branchlines only appear to have an email address!

[Anonymous]

Hey Railroading_Brit I've been looking for them, where do you get them?

[Anonymous]

Hey Railroading_Brit I've been looking for them, where do you get them?

[Anonymous]

I've seen the little Tenshodo SPUDs (it stands for Self Propelled Universal Drive), but these are powered trucks with a motor driving both axles through a worm drive system - If anyone's seen the old Tri-Ang mechanisms the design is very similar. SPUDs are handy when you want to motorize something without intruding into the bodywork - in the UK they're often used to power diesel and electric multiple units as they allow you to fit an interior. However, SPUDs have no flywheel and I suspect they wouldn't last long before burning out if you added the amount of ballast you would need to haul a decent length train!

[Anonymous]

I've seen the little Tenshodo SPUDs (it stands for Self Propelled Universal Drive), but these are powered trucks with a motor driving both axles through a worm drive system - If anyone's seen the old Tri-Ang mechanisms the design is very similar. SPUDs are handy when you want to motorize something without intruding into the bodywork - in the UK they're often used to power diesel and electric multiple units as they allow you to fit an interior. However, SPUDs have no flywheel and I suspect they wouldn't last long before burning out if you added the amount of ballast you would need to haul a decent length train!

[Anonymous]

Actually it goes counterclockwise in the Northern hemisphere and clockwise in the southern hemisphere. So what's it do at the equator?

[Anonymous]

Actually it goes counterclockwise in the Northern hemisphere and clockwise in the southern hemisphere. So what's it do at the equator?

[GDRMCo]

QUOTE: Originally posted by emeraldisle

QUOTE: Originally posted by flee307

I see you live in AU, so before I can answer that I need to know if the water swirls clockwise or anticlockwise in your toliet?

Actually, the water does go down counterclockwise, and then gets shot back out again when one of us yanks flushes up here on top of the world. You know how water pressure works. Everything runs down hill, Thats why there's so much water down there.[;)]

It goes clockwise you dofus

[GDRMCo]

QUOTE: Originally posted by emeraldisle

QUOTE: Originally posted by flee307

I see you live in AU, so before I can answer that I need to know if the water swirls clockwise or anticlockwise in your toliet?

Actually, the water does go down counterclockwise, and then gets shot back out again when one of us yanks flushes up here on top of the world. You know how water pressure works. Everything runs down hill, Thats why there's so much water down there.[;)]

It goes clockwise you dofus

[Anonymous]

QUOTE: Originally posted by flee307

I see you live in AU, so before I can answer that I need to know if the water swirls clockwise or anticlockwise in your toliet?

Actually, the water does go down counterclockwise, and then gets shot back out again when one of us yanks flushes up here on top of the world. You know how water pressure works. Everything runs down hill, Thats why there's so much water down there.[;)]

[Anonymous]

QUOTE: Originally posted by flee307

I see you live in AU, so before I can answer that I need to know if the water swirls clockwise or anticlockwise in your toliet?

Actually, the water does go down counterclockwise, and then gets shot back out again when one of us yanks flushes up here on top of the world. You know how water pressure works. Everything runs down hill, Thats why there's so much water down there.[;)]

[Anonymous]

QUOTE: Originally posted by flee307

AC is a sign wave. DCC is pulsed DC that has a positive and negative component that is phase shifted. It's like a pulsed DC power pack that has pos and neg leads and ground. The pos is +12v from ground, the neg is -12v from ground, and they are 24v apart from each other. But they are still DC.

Now we get into similarities and differences between these terms, and pulsed DC and AC can look very similar. AC is not necessarily sine wave, any waveform (including rectangular pulses) that is one polarity for 1/2 its cycle and then reverses polarity for the other 1/2 cycle is AC. This is the type of pulses used for LANs (Ethernet etc) and is chosen so it will pass through transformers at computer interfaces without distortion. Pulsed DC alternates between one polarity only, then completely off, and has an average DC value that makes DC motors run in one or the other direction. DC pulses can also be sine shaped (MRC power packs) as well as square. It is also the type of signalling used for digital logic (TTL, CMOS etc) that does not have to pass through transformers. The bridge rectifier in a DCC decoder converts the AC pulses to DC to operate the decoder logic.

But a 50% pulsed DC wave will pass through a capacitor with some distortion, and if no DC offset is added afterwards it becomes AC since it becomes centered about 0 volts and has true positive and negative reversals. If a DC offset is added it stays pulsed DC. If it is not 50% duty cycle, it becomes AC with a DC offset (one polarity is a higher voltage than the other) so in effect it becomes both together.

The main difference between AC and DC is that if you filter pulsed DC with a large capacitor, you will still get a DC voltage at the average value of the pulses. But if you filter AC the same way, you get 0 volts.

If you look at AC or DC pulses on an oscilloscope they can look identical. The only way to know what you are seeing is if you know where ground (0 volts) is in relation to the waveform.

[Anonymous]

QUOTE: Originally posted by flee307

AC is a sign wave. DCC is pulsed DC that has a positive and negative component that is phase shifted. It's like a pulsed DC power pack that has pos and neg leads and ground. The pos is +12v from ground, the neg is -12v from ground, and they are 24v apart from each other. But they are still DC.

Now we get into similarities and differences between these terms, and pulsed DC and AC can look very similar. AC is not necessarily sine wave, any waveform (including rectangular pulses) that is one polarity for 1/2 its cycle and then reverses polarity for the other 1/2 cycle is AC. This is the type of pulses used for LANs (Ethernet etc) and is chosen so it will pass through transformers at computer interfaces without distortion. Pulsed DC alternates between one polarity only, then completely off, and has an average DC value that makes DC motors run in one or the other direction. DC pulses can also be sine shaped (MRC power packs) as well as square. It is also the type of signalling used for digital logic (TTL, CMOS etc) that does not have to pass through transformers. The bridge rectifier in a DCC decoder converts the AC pulses to DC to operate the decoder logic.

But a 50% pulsed DC wave will pass through a capacitor with some distortion, and if no DC offset is added afterwards it becomes AC since it becomes centered about 0 volts and has true positive and negative reversals. If a DC offset is added it stays pulsed DC. If it is not 50% duty cycle, it becomes AC with a DC offset (one polarity is a higher voltage than the other) so in effect it becomes both together.

The main difference between AC and DC is that if you filter pulsed DC with a large capacitor, you will still get a DC voltage at the average value of the pulses. But if you filter AC the same way, you get 0 volts.

If you look at AC or DC pulses on an oscilloscope they can look identical. The only way to know what you are seeing is if you know where ground (0 volts) is in relation to the waveform.

[Anonymous]

Brush problems? Do you really have brush problems? I have never replaced a set to date.

[Anonymous]

Brush problems? Do you really have brush problems? I have never replaced a set to date.

[timmatthews]

Maybe someday the makers of model trains will incorporate Alternating Current type motors into our "toys". The technology to control their speed/torque does exist (I've been working with it for 20 years) but I've yet to hear of it in model trains.

If more than one motor were to be fitted into each loco, synchronization should not be a problem. AC motor speed can be regulated by utilizing "variable frequency control". If all motors are running from the same current source they will be synchronized.

Keep wishing for that to come about. No more brushes!

[timmatthews]

Maybe someday the makers of model trains will incorporate Alternating Current type motors into our "toys". The technology to control their speed/torque does exist (I've been working with it for 20 years) but I've yet to hear of it in model trains.

If more than one motor were to be fitted into each loco, synchronization should not be a problem. AC motor speed can be regulated by utilizing "variable frequency control". If all motors are running from the same current source they will be synchronized.

Keep wishing for that to come about. No more brushes!

[Anonymous]

AC is a sign wave. DCC is pulsed DC that has a positive and negative component that is phase shifted. It's like a pulsed DC power pack that has pos and neg leads and ground. The pos is +12v from ground, the neg is -12v from ground, and they are 24v apart from each other. But they are still DC.

[Anonymous]

AC is a sign wave. DCC is pulsed DC that has a positive and negative component that is phase shifted. It's like a pulsed DC power pack that has pos and neg leads and ground. The pos is +12v from ground, the neg is -12v from ground, and they are 24v apart from each other. But they are still DC.

[Anonymous]

see the digitrax web site appnote at http://www.digitrax.com/faqdt.htm

DCC is AC data pulses, the decoder has a rectifier and pulse modulator to convert the AC data packets to controlled DC pulses for the motor. If AC is applied directly to an AC motor, it could not run in reverse unless the field winding is reversed; DC motors use permanent magnets instead so they can be made smaller. Also the drive gearing allows a lot more low speed torque to be applied to the wheels with the motor running at a higher speed, kinda like first gear in a car. Direct drive would lose all this torque.

I had an American Flyer S scale as a kid, it must have been AC powered since to reverse one had to fully stop the train, then apply power again to cause a stepping relay in the tender to swap field winding polarity. Then re-apply power to run in reverse; repeating the sequence would set it to forward again. That was in the days before silicon diodes were available and the usual selenium type rectifier had way too much resistance for low voltage, so AC and a variable turns ratio transformer was the only way to go other than batteries and rheostat. But they still geared the motor down.

PS Mine all swirl counterclockwise. Is that correct for the Northern hemisphere? If not that Coriolis force thing just got debunked.

[Anonymous]

see the digitrax web site appnote at http://www.digitrax.com/faqdt.htm

DCC is AC data pulses, the decoder has a rectifier and pulse modulator to convert the AC data packets to controlled DC pulses for the motor. If AC is applied directly to an AC motor, it could not run in reverse unless the field winding is reversed; DC motors use permanent magnets instead so they can be made smaller. Also the drive gearing allows a lot more low speed torque to be applied to the wheels with the motor running at a higher speed, kinda like first gear in a car. Direct drive would lose all this torque.

I had an American Flyer S scale as a kid, it must have been AC powered since to reverse one had to fully stop the train, then apply power again to cause a stepping relay in the tender to swap field winding polarity. Then re-apply power to run in reverse; repeating the sequence would set it to forward again. That was in the days before silicon diodes were available and the usual selenium type rectifier had way too much resistance for low voltage, so AC and a variable turns ratio transformer was the only way to go other than batteries and rheostat. But they still geared the motor down.

PS Mine all swirl counterclockwise. Is that correct for the Northern hemisphere? If not that Coriolis force thing just got debunked.

[dknelson]

I seem to recall that years and years ago American Flyer had some HO which might have been AC. That was back when DC motors were usually 6 volt. Before my time actually.
Anyway as to mounting motors on the axles that should work and there was a product called the SPUD which could do this. It was a small DC motor with, I think, the axle shaft also part of the motor shaft.
That way for example a tunnel motor could actually have a see-through rear vent, and trolleys could have detailed interiors. But if each axle was a motor I do not know about current draw and frankly I do not know if I ever saw an article on converting SPUDs to DCC for that matter.
Dave Nelson

[dknelson]

I seem to recall that years and years ago American Flyer had some HO which might have been AC. That was back when DC motors were usually 6 volt. Before my time actually.
Anyway as to mounting motors on the axles that should work and there was a product called the SPUD which could do this. It was a small DC motor with, I think, the axle shaft also part of the motor shaft.
That way for example a tunnel motor could actually have a see-through rear vent, and trolleys could have detailed interiors. But if each axle was a motor I do not know about current draw and frankly I do not know if I ever saw an article on converting SPUDs to DCC for that matter.
Dave Nelson

[Anonymous]

Not to mention the obvious. Marklin & Lionel AC.

However, the track voltage for DCC is actually pulsed DC, not AC, and an inverter is big & heavy.