Cool. I hear you I had a 26 hour day yesterday so not much good today.
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TCI Replacement 2020 It Works
- Thread starter Team Junk
- Start date
Dummy here but wouldn't grounding the "other" pick up lead to the common work "just fine"?
Needs some resistance to prevent the coil burning out. It would be the same as shorting one of the stator wires.
EDIT
It might be ok to short it but I dislike might be. Same concept as close might be fine in horseshoes and handgrenades.
EDIT
It might be ok to short it but I dislike might be. Same concept as close might be fine in horseshoes and handgrenades.
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Well I got educated (I think) in some regulator threads, a "shorted" loop like that will not heat cuz there's no load. But have not tested the theory...
A short is a maximum load. That's how a shunt pma regulator works by shorting the coil to ground to put a load on the coil to reduce the voltage.
I keep seeing the other side of that argument that leaving a stator coil open will burn it up. No current can flow from an open coil just like a battery won't work with one cable off. Generating coils are a voltage source just like a battery and they don't like to be shorted ether..
In fact opening the connection to the coil is how the newer series regulators work.
Least that's my understanding of the world.
I thought I should mention that this is a very simplified description of how PMA alternator regulators work.
In fact I think this misunderstanding is what causes a lot of PMA stator failures.
In fact I think this misunderstanding is what causes a lot of PMA stator failures.
Just a real world observation was my ke100 pit bike. It ran for years with nothing connected to the lighting coil until I decided to put plates on it. After years of running with no load on the coil, when I hooked it up it worked fine.
The only heating on a open coil is eddy currents but that is a whole different conversation.
I think the open coil thing started with the fact that you can damage a car alternator by disconnecting it from the battery. That kills the diodes, not the coils.
power = volts x current. if a a magnet passing a coil makes a certain amount of power (notice pma 's are rated in watts) the regulator can't change how many watts a coil puts out. That is set by the size of the magnet and the amount of henry's in the coil. so if the regulator is trying to regulate a coil that produces 100 watts and at the rpm it makes max wattage it produces 50v then 50v x 2 amps =100 watts then to make 100 watts at 10v(much closer to 0V), would be 10 amps. The series regulators run cooler because they block the current flow instead of shunting it to ground.
Edit
In order for a shunt regulator to regulate to 12V with a 24 watt load volts the regulator has to provide the load 24 watts(12V x 2A) and shunt to ground 76W (12V x 6.33A). Think about the heat a 75 watt bulb makes. That's why a shunt regulator gets so hot.
Edit
In order for a shunt regulator to regulate to 12V with a 24 watt load volts the regulator has to provide the load 24 watts(12V x 2A) and shunt to ground 76W (12V x 6.33A). Think about the heat a 75 watt bulb makes. That's why a shunt regulator gets so hot.
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Quoting Paul Sutton
The voltage output of a shorted PMA stator is very close to 0 volts. This means the power dumped through the stator is also very low since Power = Volts x Current.
Don't confuse low voltage with low power. The amount of power in the sator is constant regardless of the voltage it is regulated to. If the voltage goes down the current must go up
100 watt bulb. 100v = 1 amp
10v =10amps
The voltage output of a shorted PMA stator is very close to 0 volts. This means the power dumped through the stator is also very low since Power = Volts x Current.
Don't confuse low voltage with low power. The amount of power in the sator is constant regardless of the voltage it is regulated to. If the voltage goes down the current must go up
100 watt bulb. 100v = 1 amp
10v =10amps
Did manage to get a new pigtail done for the gonzo non grounded box. Will hook it up to the test stand tomorrow.
And back to the premise that shorting a coil is not a good thing..
Your house is fed power from a coil of wire that has a magnetic field rotating past it.
What happens when you short the hot wire and ground wire. (that's why we have breakers) A hi current flow that without the breaker would fry the coil (Transformer Blows up)
Your house is fed power from a coil of wire that has a magnetic field rotating past it.
What happens when you short the hot wire and ground wire. (that's why we have breakers) A hi current flow that without the breaker would fry the coil (Transformer Blows up)
Ohm's law calculator for anyone interested.
https://www.allaboutcircuits.com/tools/ohms-law-calculator/
https://www.allaboutcircuits.com/tools/ohms-law-calculator/
The main article I read warned against applying alternator theory to a PMA. Both have quite different characteristic. A PMA is unique compared to a conventional automotive alternator and this is why it is safe to short them. One unique PMA property is the constant current output with rpm. The heating in a PMA system comes from the SCR acting as a load during part of its switching cycle. The MOSFET is a better switching device for a PMA giving a cleaner transition from off to on without acting as a load, hence the lower heat generation. When a PMA is shorted the voltage goes to zero but the current is still there. However the direction of current flow is poorly defined and not all flows in and out of the coil. PMA coils do not burn out when shorted. The damage to the PMA coils is believed to result when the regulator/rectifier suffers diode failure and allows the battery to dump power back through the coils. For this reason it is recommended to add a fuse between the Battery and Reg/Rectifier.
If that advance coil is left open and acts as a PMA it will build a very high voltage and possibly transmit electrical interference. Placing a resistor across it should calm it down but you may have to experiment with the resistor value to see what works best. Shorting the coil should be viable also. Maybe we have the makings of a science project?
If that advance coil is left open and acts as a PMA it will build a very high voltage and possibly transmit electrical interference. Placing a resistor across it should calm it down but you may have to experiment with the resistor value to see what works best. Shorting the coil should be viable also. Maybe we have the makings of a science project?
I have done a little science project this afternoon. I broke up a miniature PCB relay with 6 pins to get the coil then glued it to a scrap of metal to mount in the lathe tool post.:
I also took a piece of broom handle and glued 4 Neodymium magnets (6mmOD x 3mm thick) at 90 Degree intervals. When setup in the lathe this gives a simulator of some sort:
Each rpm is 4 pulses. The coil has a resistance of 335 Ohm and boy is it a cute one. I set the gap between the coil's non-magnetic core and the magnets for approximately 1mm based on me knowing the XS has at least a 0.5mm clearance at the rotor. All voltage and current readings were done on the AC setting. Voltage reading were made with a 4.7kOhm load across the coil and Current reading were made with a 4.7kOhm load in series. I also measured currents without a 4.7k resistor in place i.e. the meter was the load and I call this a zero load current.So here goes:
330 rpm (1320 pulses per minute)
0.2mA
0.97V
Zero Load 4.3mA
1500 rpm (6000 pulses per minute)
1.0mA
4.7V
Zero Load 17.5mA
2400 rpm (9600 pulses per minute)
1.4mA
6.8V
Zero Load 23.6mA
So what does it mean? As a PMA it is very poor and this is due to the high internal resistance of 335 Ohm. Stators are typically less than 1 Ohm.
I did a side experiment by holding at 1500 rpm (6000 pulses per minute) and varied the distance between the coil core and the magnet:
0.25 mm 5.9V 1.2mA
1.0 mm 4.7V 1mA
2.5 mm 2.9V 0.5mA
Well, no surprises there.
Because I am curious about PMAs I decided to short circuit the coil at 2400 rpm (9600 pulses per minute) and see what happens. Well actually nothing. I ran it for 10 minutes and monitored the resistance:
0 min 335 Ohm
5 min 335 Ohm
10 min 335 Ohm
I saw no temperature resistance variation. After 10 minutes I touched the coil against a very sensitive part of my anatomy, you guessed it, my lip. I observed no sign of heating.
So what do I conclude - it is safe to short out these higher resistance coils if I wish.
Minor Distraction: Those cute little relay coils would make a fab little ignition pickup when suitably mounted i.e. potted with epoxy in a little metal frame/box.
Must go now, roast lamb calling.
I also took a piece of broom handle and glued 4 Neodymium magnets (6mmOD x 3mm thick) at 90 Degree intervals. When setup in the lathe this gives a simulator of some sort:
Each rpm is 4 pulses. The coil has a resistance of 335 Ohm and boy is it a cute one. I set the gap between the coil's non-magnetic core and the magnets for approximately 1mm based on me knowing the XS has at least a 0.5mm clearance at the rotor. All voltage and current readings were done on the AC setting. Voltage reading were made with a 4.7kOhm load across the coil and Current reading were made with a 4.7kOhm load in series. I also measured currents without a 4.7k resistor in place i.e. the meter was the load and I call this a zero load current.So here goes:
330 rpm (1320 pulses per minute)
0.2mA
0.97V
Zero Load 4.3mA
1500 rpm (6000 pulses per minute)
1.0mA
4.7V
Zero Load 17.5mA
2400 rpm (9600 pulses per minute)
1.4mA
6.8V
Zero Load 23.6mA
So what does it mean? As a PMA it is very poor and this is due to the high internal resistance of 335 Ohm. Stators are typically less than 1 Ohm.
I did a side experiment by holding at 1500 rpm (6000 pulses per minute) and varied the distance between the coil core and the magnet:
0.25 mm 5.9V 1.2mA
1.0 mm 4.7V 1mA
2.5 mm 2.9V 0.5mA
Well, no surprises there.
Because I am curious about PMAs I decided to short circuit the coil at 2400 rpm (9600 pulses per minute) and see what happens. Well actually nothing. I ran it for 10 minutes and monitored the resistance:
0 min 335 Ohm
5 min 335 Ohm
10 min 335 Ohm
I saw no temperature resistance variation. After 10 minutes I touched the coil against a very sensitive part of my anatomy, you guessed it, my lip. I observed no sign of heating.
So what do I conclude - it is safe to short out these higher resistance coils if I wish.
Minor Distraction: Those cute little relay coils would make a fab little ignition pickup when suitably mounted i.e. potted with epoxy in a little metal frame/box.
Must go now, roast lamb calling.
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And we come full circle. I agree with Paul on the regulation of PMA's
The point of the discussion was about shorting across a generating coil . A open coil has zero current flow so very little heat is generated. When the coil is shorted the maximum amount of heat is generated. While it might not immediately fail, the heat generated in the coil by shorting it will eventually cause the lacquer coating to fail.
The pickup coil is a PMA, but it is optimized to create a high voltage and low current so at cranking speed there is enough signal for the igniter to trigger. The input to the igniter is (especially on the gonzo box) is very high so very little load is placed on the coil allowing it to make as much voltage as possible with little current flow. The pickup coil is wound with very fine wire so it's current capacity is low.
On the other hand the charging coils in a PMA are wound with heavy gauge wire optimized to create current instead of voltage. The heavy wire allows a much lower resistance load to be placed across it
The science project aspect is to load the pickup enough to reduce it's voltage output (and noise) to a level that won't trigger the box.
The point of the discussion was about shorting across a generating coil . A open coil has zero current flow so very little heat is generated. When the coil is shorted the maximum amount of heat is generated. While it might not immediately fail, the heat generated in the coil by shorting it will eventually cause the lacquer coating to fail.
The pickup coil is a PMA, but it is optimized to create a high voltage and low current so at cranking speed there is enough signal for the igniter to trigger. The input to the igniter is (especially on the gonzo box) is very high so very little load is placed on the coil allowing it to make as much voltage as possible with little current flow. The pickup coil is wound with very fine wire so it's current capacity is low.
On the other hand the charging coils in a PMA are wound with heavy gauge wire optimized to create current instead of voltage. The heavy wire allows a much lower resistance load to be placed across it
The science project aspect is to load the pickup enough to reduce it's voltage output (and noise) to a level that won't trigger the box.
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Great experiment Paul, thank you!
I think the point (he proved?) is with the coil permanently shorted no voltage rise, therefore no heat, zero volts no wattage possible. Should also stop any egregious signals.
It's not my kettle of fish so was just throwing it out as a suggestion.
would be interesting to see if a full short causes the magnet to resist spinning I recall doing some "wind turbine" experiments way back and was impressed how much a small wattage bulb changed the resistance felt by the blades. But never tried a direct short. My feeling is if there is resistance then work is being done and there will be heat.
I think the point (he proved?) is with the coil permanently shorted no voltage rise, therefore no heat, zero volts no wattage possible. Should also stop any egregious signals.
It's not my kettle of fish so was just throwing it out as a suggestion.
would be interesting to see if a full short causes the magnet to resist spinning I recall doing some "wind turbine" experiments way back and was impressed how much a small wattage bulb changed the resistance felt by the blades. But never tried a direct short. My feeling is if there is resistance then work is being done and there will be heat.
