Circuit setups for pulse motors

[Ren]

@Ren,
I meant to get back to you on this issue of mechanical power. As you may/already have discover/ed, 24 watts motor running on a Voltage of 24 Volts X 1 Amp, yields a higher mechanical efficiency than a 24 watts motor running on voltage of 12 Volts X 2 Amps.
Why? Power lost through Heat which is driven by current consumption.

But which has the maximum absolute torque? The less efficient 12 Volt X 2 Amps system. Why?. Because current does create the magnetic field strength of an electromagnetic core.

Is it possible to get the best of both higher voltage and higher current without actually contributing the higher current directly?
YES.

Ren you indicated that you were looking at mechanical efficiency in your recent switch to a 24 Volts supply. That's a good move to the higher supply, because it allows you to use high impedance coils (which you already are! 3000 turns? from memory?)

Try taking a lateral step sideways, and separate your drive coil function from your trigger coil function. You can do this by winding a fine
.1mm wire coil onto a small steel nail or screw core and using it as a separate trigger coil which can be physically placed wherever you want it. With fine wire you can wind 400-500 turns or more. By separating the drive and trigger coil, you can better adjust the actual pulse width of the trigger, but also more importantly the pulse angle with respect to the drive coil.

You may need to put a diode directly across the new trigger coil in opposite direction to the base to emiiter/sink connection of your Transistor/Mosfet. You can still use pots in line with the transistor to fine tune the pulse.

Now to the subject of higher current without paying the price of consumption. You may remember that efficient use of a collapsing field will be maximized when the total "Virtual Drive" pulse of the core is less than or equal to 50%. High impedance cores can have a long "time constant" when the Collapsing field is discharged through an electrical regeneration or torque enhancing circuit.

That's where a step-down transformer output coil and a tightly controlled short duty cycle come into their best effect.
Try winding a 150 - 300 turns high diameter (.62 - . coil outside your drive coil. The low impedance step-down coil when shorted by a Diode in the correct polarity direction, will provide a high current at the collapse of the main drive coil, but it will possess a short "time constant" and this will ensure a greater chance of the Virtual Pulse (usable Pulse) to remain under 50% and still be significantly longer than the Actual Pulse (current consumption).

Bear in mind, this will turn all the Collapsing EMF and "in-phase" rotational Magnet Induced EMF into mechanical torque, at the expense of CEMF electrical regeneration. Its' a choice of one or the other using this method.

Cheers from the Toad Who Hops 
[/quote]

Thanks for the tips Toad. I have tried the separate pickup coil and it works well. Definately something I need to experiment with.

I have a question regarding your comments about losses attributed to heat. I understand the principle of what you describe however I wonder how relevant it is to my build? I have approx 850 trifilar turns on my coil which displays no indication of any temperature change while running. Same with the circuit. Is there something I am missing...voltage drop across components? BUT is voltage drop over, say, a diode largely attributed to heat?

The small batteries I have been charging are sitting at 13.10 volts after resting overnight. I just drained one at its C20 and after 8 hours it rested at 12.57 volts.

I built another speed device which cranks, but draws a little too much for my liking. I might convert that to run off a separate pickup coil. Magnets are sealed in resin on this device which makes it alot safer!

[hoptoad]

I have a question regarding your comments about losses attributed to heat. I understand the principle of what you describe however I wonder how relevant it is to my build? I have approx 850 trifilar turns on my coil which displays no indication of any temperature change while running. Same with the circuit. Is there something I am missing...voltage drop across components? BUT is voltage drop over, say, a diode largely attributed to heat?

The small batteries I have been charging are sitting at 13.10 volts after resting overnight. I just drained one at its C20 and after 8 hours it rested at 12.57 volts

I built another speed device which cranks, but draws a little too much for my liking. I might convert that to run off a separate pickup coil. Magnets are sealed in resin on this device which makes it alot safer!

@Ren,
I have a few questions of my own which will help you answer your own question.

What is the DC resistance of the drive filament of your 850 turns tri-filar coil?
What is the Copper weight of the entire tri-filar coil?
What is the Current Consumption of the motor at its full running speed without a mechanical or regenerative load?
Does the Current Consumption of the motor increase dramatically or moderately when a mechanical or regenerative load is applied?
Does the motor slow down considerably when a load is placed upon it?
What is the RPM of the rotor? And how many magnets on the rotor dictating the final frequency of the pulse at full speed?
Do you know the actual duty cycle of the pulse?

Does your motor take a while to reach full speed?
Is it easily stopped when running at full speed?

The answers to the first seven questions will help you to understand the answer to the last two questions and your question regarding heat.
If the answers to the last two questions are Yes, then you are running a low torque motor, because you are only consuming a small amount of current, even under load.

If this is the case, then voltage drops across the coil and all components in series with the coil will be minimum.
Less current, less heat in everything!

Because the coil has a variable impedance which is dependent on pulse frequency, then increased loading will cause increased current consumption as the frequency drops due to rotor slowing.

But the decreasing frequency of the pulses associated with a slowing rotor, not only causes a drop in inductive reactance of the coil, but also a drop in true applied power as the pulses occur less often in real time. So power consumption will not rise dramatically with a load, but there may be a considerable slowing of the rotor due to that load and a resultant diminished applied EMF (That is less current available under load than with normal DC).

The heat from a diode is the result of the voltage drop within the diode caused by the internal resistance to current of the diode. The more current a diode has to conduct, the hotter it will become. The power dissipation of the diode will be the Voltage Drop X Current.

Cheers All from The Toad Who Hops.........KneeDeep and Happy Motoring! 

[Ren]

What is the DC resistance of the drive filament of your 850 turns tri-filar coil?

By this you mean ohms? Around 17 ohms for each power coil. Theres two firing and the third is the trigger.


What is the Copper weight of the entire tri-filar coil?

I didnt measure, but I would guestimate at just over 750g

What is the Current Consumption of the motor at its full running speed without a mechanical or regenerative load?

I can vary current consumption. I am still testing. It will run on 25ma up to 300ma, higher with less resistance. I currently run it in between 60 and 100ma for a reasonable speed. This is without a load (well the wheel is 1.5 kilos +) BUT charging on the backend. Funnily enough it doesnt consume much more @ 24v.

Does the Current Consumption of the motor increase dramatically or moderately when a mechanical or regenerative load is applied?

Mechanical loading only causes the current consumption to drop as per all ssg circuits. I only ever run it with a charging bank connected as to ensure the safety of the circuit, i.e no blowing the transistors. Testing showed that current can drop a little when a charging bank is connected.


Does the motor slow down considerably when a load is placed upon it?

Yes, but you have to consider the scale. When a mechanical load, i.e. my finger is placed on the outer diameter the wheel will come to a stop quite quickly. When pressure is applied to the shaft it is significantly better for obvious reasons. Overall Im pretty happy with how much mechanical it can do for how little it draws.

What is the RPM of the rotor? And how many magnets on the rotor dictating the final frequency of the pulse at full speed?

An accurate RPM is unknown, there are eight north pole out mags.

Do you know the actual duty cycle of the pulse?

Woah easy tiger! lol. I wish mate. I only have the basics. DMM's etc. I want to save up for a scope and various other hardware soon.

[hoptoad]

Overall Im pretty happy with how much mechanical it can do for how little it draws.
Woah easy tiger! lol. I wish mate. I only have the basics. DMM's etc. I want to save up for a scope and various other hardware soon.

@Ren , LOL   Just thought I'd fire from the hip with all the questions.! LOL sorry!
Will get back to you very soon. Teas on the table! Cheers

[Ren]

lol, all good shooter mcgavin, enjoy ya din din