Topic: 1978 CB550K charging: difference between field and stator coil?

[AirCanuck]

I thought these were interchangeable terms, field coil and stator coil.  However, reading the 1978 CB550K servicing manual, first thing it says is

"The charging system for the CB500 is made up of the exciter field 3-phase AC generator, rectifier, voltage regulator and the fuse.  The generator consists of the field coil, stator coil and the rotor..."

So obviously I'm mistaken.  What's the difference? 

I am dealing with a charging issue on my bike.  I am having a garage handle it in the interests of getting it on the road ASAP, but I really want to be able to discuss the work they're doing and eventually be able to do everything required by myself.

thanks!

cheers,

AirCanuck

[TwoTired]

The stator is where the ac power comes out. It needs a varying magnetic field to generate this power.  The magnetic field is created by the field coil.  And the field variation is created by the rotor.  The vregulator varies the field strength in response to the battery charge state.

Need more info?

Cheers,

[CycleRanger]

#12, 13, 14.
From the parts list available here:
http://www.honda4fun.com/materiale-documentazione-tecnica/parts-list/parts-list-cb550

 

[calj737]

For the price of a decent multimeter, and about 30' of your time, probably you could resolve the charging issue yourself. Most shops will reduce "charging issues" to replacing your stock Regulator and Rectifier with a new, solid state unit, which may or may not be your actual problem.

Corrosion on terminal plugs and connections, previous owner hack jobs and poor splices, and poor grounds comprise most of the issues. These issues cause resistance which in turn reduces the components ability to generate a proper charge. Not to mention a bad battery.

Go recover your bike and stop by the Auto Store and grab a meter ($50). Then TwoTired will forward to you his detailed, step-by-step outline for charging system analysis. Then your bike will be much better off and your wallet less dented.

[AirCanuck]

The stator is where the ac power comes out. It needs a varying magnetic field to generate this power.  The magnetic field is created by the field coil.  And the field variation is created by the rotor.  The vregulator varies the field strength in response to the battery charge state.

Need more info?

Cheers,

I'd love more info.  I fly turboprop aircraft and SORT OF understand how a generator works but to be honest it's always been someone black magic to me.

I understand the need to rectify AC generated power to DC power for the battery, and that the battery supplies the power for the bike's systems. 

I don't understand why the magnetic field needs to be varying, or how the field coil causes it to vary.  I guess while in general I understood what you wrote, conceptually I don't really understand most of what's there, but I would like to.  The same thing came of me reading the Honda Service Manual which describes the charging system in detail.

[madmtnmotors]

The field coil on these old bikes is an electro magnet in that it needs voltage to create the magnet. The field coil is just a lump of iron with copper wire wound around it. The regulator regulates voltage to the field coil to vary the strength of the magnet to regulate voltage output of the stator coil. Newer alternators use a permanent magnet and the regulators on newer systems simply shunt the alternator's voltage output instead.

[TwoTired]

A compressed tutorial....
A magnet produces lines flux radiating from its north and south poles, not visible to the unaided eye.  When these lines of flux cross a piece of wire, the electrons inside the wire become excited and this produces a voltage.  The lines of flux must be changing to continue excitation, ideally alternating from north to south orientation relative to the magnet's poles.

The stator wires/ windings are the object to which the north/ south crossings are directed.

Electromagnets are comprised of a ferous core within an electrical field.  This polarises the metal to create north and south poles. This is what the field coil does, using the rotor as it ferous core.  The core is slotted and mechanically arranged to create alternating north and south poles along its circumference.  Energize the field coil and rotate the core (rotor), and alternating positive and negative voltage is excited in the stator core in three phases.  The rectifier turns the AC into DC for use in recharging the battery or consumption by end use devices.

The voltage regulator monitors the battery voltage level, and bolsters or depletes the field current for the alternator in order to prevent battery damage from overcharge while in cruise mode.


In a nutshell...  Visual aids would help, I'm sure.  But, that's not going to happen using this very old IPad.
In a couple weeks I'll be back to the computer in CA. Pictures drawings then a posibility.

Cheers,

[AirCanuck]

The field coil on these old bikes is an electro magnet in that it needs voltage to create the magnet. The field coil is just a lump of iron with copper wire wound around it. The regulator regulates voltage to the field coil to vary the strength of the magnet to regulate voltage output of the stator coil. Newer alternators use a permanent magnet and the regulators on newer systems simply shunt the alternator's voltage output instead.

Yes, PMGs I recognize from my work with turbine engines... Another thing I don't get - why if the battery dies will the bike stop running?  Doesn't a car keep going if the battery is dead once boosted?  Is that because the alternator would be keeping it going in that scenario, vs a bike with a bad charging system?

[AirCanuck]

A compressed tutorial....
A magnet produces lines flux radiating from its north and south poles, not visible to the unaided eye.  When these lines of flux cross a piece of wire, the electrons inside the wire become excited and this produces a voltage.  The lines of flux must be changing to continue excitation, ideally alternating from north to south orientation relative to the magnet's poles.

The stator wires/ windings are the object to which the north/ south crossings are directed.

Electromagnets are comprised of a ferous core within an electrical field.  This polarises the metal to create north and south poles. This is what the field coil does, using the rotor as it ferous core.  The core is slotted and mechanically arranged to create alternating north and south poles along its circumference.  Energize the field coil and rotate the core (rotor), and alternating positive and negative voltage is excited in the stator core in three phases.  The rectifier turns the AC into DC for use in recharging the battery or consumption by end use devices.

The voltage regulator monitors the battery voltage level, and bolsters or depletes the field current for the alternator in order to prevent battery damage from overcharge while in cruise mode.


In a nutshell...  Visual aids would help, I'm sure.  But, that's not going to happen using this very old IPad.
In a couple weeks I'll be back to the computer in CA. Pictures drawings then a posibility.

Cheers,

Thank you! certainly helpful, and definitely images would also help.  As would a similar discussion and images on carbs, specifically those modded with air pods which mine are.  Of course, if you don't have a favourite source off hand I'm sure I can hunt down an explanation by the hundreds on Google...

[Deltarider]

Another thing I don't get - why if the battery dies will the bike stop running?

Normally it doesn't as demonstrated by some brave Dutchman (not me). See vid.

[TwoTired]

Yes, PMGs I recognize from my work with turbine engines... Another thing I don't get - why if the battery dies will the bike stop running?  Doesn't a car keep going if the battery is dead once boosted?  Is that because the alternator would be keeping it going in that scenario, vs a bike with a bad charging system?

PMGs are permanent magnet generators.  They are always magnetized and only need rotation to create power.
Electromagnets are only magnetized when provided power.  The SOHC4 has an electromagnet (field coil and rotor).

The ignition circuit needs power to make spark.  A dead battery can't provide power for spark or energize the field coil.  Therefore, no spark.

While a spinning alternator can provide enough power to self excite after jump starting, it has to provide more power than the bike is using.  If you turn off non-essentials, and if the rotor is spinning fast enough, the motor will keep running. However, if rpm drops low enough to starve field coil and ignition, the bike will stop.

However, doing so has some risk involved.  The battery absorbs and stabilizes the voltage output spikes from the alternator.  Without it, the alternator can create voltage spikes far higher than with the battery present.  These voltage spikes can harm or weaken the rectifier diodes.   You can jump off some cliffs safely.  You cannot jump off all cliffs safely.
There is no good reason to add stress to your electrical system unnecessarily.
But, people do foolish things and often get away with it.  Doesn't prove there is no cost in all cases.

A car's alternator spins fast enough (pulley ratios) to provide all the power the car needs at idle RPM.
The SOHC4 alternator doesn't normally provide enough power for max consumption at idle, and draws from the battery to keep systems working.
Most people don't buy these bikes to sit around idling all day.

Cheers,

[madmtnmotors]

why if the battery dies will the bike stop running?

If the battery dies, where will you get the power to energize the electro magnet? Without a magnet there is no charging "field".

Doesn't a car keep going if the battery is dead once boosted?

Yes, because their alternators (as well as the alternators on newer bikes) use permanent magnets. 

[AirCanuck]

Yes, PMGs I recognize from my work with turbine engines... Another thing I don't get - why if the battery dies will the bike stop running?  Doesn't a car keep going if the battery is dead once boosted?  Is that because the alternator would be keeping it going in that scenario, vs a bike with a bad charging system?

PMGs are permanent magnet generators.  They are always magnetized and only need rotation to create power.
Electromagnets are only magnetized when provided power.  The SOHC4 has an electromagnet (field coil and rotor).

The ignition circuit needs power to make spark.  A dead battery can't provide power for spark or energize the field coil.  Therefore, no spark.

While a spinning alternator can provide enough power to self excite after jump starting, it has to provide more power than the bike is using.  If you turn off non-essentials, and if the rotor is spinning fast enough, the motor will keep running. However, if rpm drops low enough to starve field coil and ignition, the bike will stop.

However, doing so has some risk involved.  The battery absorbs and stabilizes the voltage output spikes from the alternator.  Without it, the alternator can create voltage spikes far higher than with the battery present.  These voltage spikes can harm or weaken the rectifier diodes.   You can jump off some cliffs safely.  You cannot jump off all cliffs safely.
There is no good reason to add stress to your electrical system unnecessarily.
But, people do foolish things and often get away with it.  Doesn't prove there is no cost in all cases.

A car's alternator spins fast enough (pulley ratios) to provide all the power the car needs at idle RPM.
The SOHC4 alternator doesn't normally provide enough power for max consumption at idle, and draws from the battery to keep systems working.
Most people don't buy these bikes to sit around idling all day.

Cheers,

Fantastic explanation, thank you!!

[AirCanuck]

Just want to thank everyone for their kind advice and explanations, I love this site!

[AirCanuck]

For the price of a decent multimeter, and about 30' of your time, probably you could resolve the charging issue yourself. Most shops will reduce "charging issues" to replacing your stock Regulator and Rectifier with a new, solid state unit, which may or may not be your actual problem.

Corrosion on terminal plugs and connections, previous owner hack jobs and poor splices, and poor grounds comprise most of the issues. These issues cause resistance which in turn reduces the components ability to generate a proper charge. Not to mention a bad battery.

Go recover your bike and stop by the Auto Store and grab a meter ($50). Then TwoTired will forward to you his detailed, step-by-step outline for charging system analysis. Then your bike will be much better off and your wallet less dented.

I really want to do this.  However, I am about to leave the country possibly for a couple weeks with the military and I'd love for my bike to be road-worthy when I get back.  I wish it wasn't riding season and I would see this through myself!  However if I find out their quote is enormous to move beyond the current step (which is replacing the stator) I will do it myself anyway, delays or no.

[TwoTired]

SOHC 4 Stators only go bad with crash damage or a berserker with a battle axe.
They better prove to you it is bad and why, or they are just robbing your wallet.

Cheers,

[BomberMann650]

That's not to mention the additional price some shops charge to work on any "vintage" bike.

Because apparently, it takes an extra $30 to solve a problem that plagues EVERY motorbike make and model, at least once 🙄

[RAFster122s]

Most cars will stop running once the battery dies even if the regulator has not. 
I have seen batteries fail and result in damage to the charging system, regulator on alternator.
Regulator failed after individual charged battery out of car multiple times after it began failing overstressing the alternator's regulator causing it to fail.

 

The field coil on these old bikes is an electro magnet in that it needs voltage to create the magnet. The field coil is just a lump of iron with copper wire wound around it. The regulator regulates voltage to the field coil to vary the strength of the magnet to regulate voltage output of the stator coil. Newer alternators use a permanent magnet and the regulators on newer systems simply shunt the alternator's voltage output instead.

Yes, PMGs I recognize from my work with turbine engines... Another thing I don't get - why if the battery dies will the bike stop running?  Doesn't a car keep going if the battery is dead once boosted?  Is that because the alternator would be keeping it going in that scenario, vs a bike with a bad charging system?

[jonda500]

Another thing I don't get - why if the battery dies will the bike stop running?

Normally it doesn't as demonstrated by some brave Dutchman (not me). See vid.

Cars are the same (at least all that I've tried it with were) - they will run with no battery once started

A dead battery that has internally shorted out may be worse than no battery?

John

[Deltarider]

A dead battery that has internally shorted out may be worse than no battery?

Probably.

[AirCanuck]

SOHC 4 Stators only go bad with crash damage or a berserker with a battle axe.
They better prove to you it is bad and why, or they are just robbing your wallet.

Cheers,

geeze, I don't know what to think.

The guys I'm dealing with have a good reputation.  They are a small local custom shop.  They also called me to warn me before they started that they weren't sure how long or how much this was going to take, and if I wanted to take it and try my luck on my own or with someone else I was free to.

The point is, they didn't really seem to be trying to take me for a ride.  My buddy today is bringing me a stator and cover for $100CAD so that's not too bad.  Rebuilding it would have cost more and taken a lot more time for shipping etc here in good ol' Canada.

I'll see what comes next.  If things start getting ridiculous I'll have to try it myself.  Oh, bonus points, I live in a military base house currently so no garage to work on it in. 

[TwoTired]

It is not uncommon for the field coil to fail and need replacement.  It has smaller diameter wires that can vibrate about and chafe against things.

The stator wires are much larger diameter, and don't bend much at all with vibration.  Also, by design they can't be over taxed beyond capability with too heavy loads, as their output is self limiting.
While not totally impossible, stators just don't go bad without some sort of physical attack upon them.

If the technician is mostly familiar with permanent magnet alternators that have no field coil, it is logical that they would assume an alternator not giving output would have a bad stator.  However, a competent shop should be able to test a stator with a quality low ohms meter to prove the stator is actually bad.

Cheers,

[AirCanuck]

It is not uncommon for the field coil to fail and need replacement.  It has smaller diameter wires that can vibrate about and chafe against things.

The stator wires are much larger diameter, and don't bend much at all with vibration.  Also, by design they can't be over taxed beyond capability with too heavy loads, as their output is self limiting.
While not totally impossible, stators just don't go bad without some sort of physical attack upon them.

If the technician is mostly familiar with permanent magnet alternators that have no field coil, it is logical that they would assume an alternator not giving output would have a bad stator.  However, a competent shop should be able to test a stator with a quality low ohms meter to prove the stator is actually bad.

Cheers,

I asked him what was wrong with it and he said it "wasn't charging", wasn't testing properly.  I found out there was a guy nearby who really knows vintage Hondas and moved it there.  We'll see what he finds!

[TwoTired]

Probably a good move.

Keep us posted!

[AirCanuck]

Probably a good move.

Keep us posted!

will do.. question for you...

The bike has the ricks motorsport regulator/rectifier installed under the cafe seat.  I heard they need good airflow.  I asked the builder about it and he said they don't get that hot, he has seen other builders do the same thing.

thoughts?