ZFM Advanced Explorations Part II

[Yaro1776]

6 Pole ZFM with Coils in Parallel

Completing the test program of the 6 Pole ZFM was a series of experiments with the bifilar coils wired in a parallel configuration versus the prior Post's series configuration. The overall three coil parallel resistance was 1.5 ohms compared to 6.0 ohms for the prior series arrangement. The parallel configuration was tested with and without the BEMF recovery circuit and with the 60v Power supply and 24v LABs for comparison. Only the 24v data will be presented at this time.

The coils in parallel create a different mode of ZFM operation. The amperage draw is nearly double the series mode value for a given run voltage, while the RPM is also nearly twice the series value. The impression is that the motor is running at a much higher voltage. All in all, this mode creates a very tractable motor for certain applications with power efficiencies very close to or at 50%. The 4 Pole ZFM will display similar characteristics when properly configured in parallel mode.

Below is a sample of the data points for both options. The ZFM has slightly different characteristics between the two types of applied power - the LAB runs required a timing adjustment to compensate. The attached pics were all generated under no Load. Pic 2 demonstrates the oscope wave form for the LAB without the BEMF circuit, while Pic 3 with the BEMF circuit engaged. The Power supply mode with the BEMF circuit engaged is nearly identical to Pic 3 and not included.

Parallel Mode with Power Supply no BEMF Circuit (Pic 1)
4360 RPM 24.01v 0.60A 0gr Load
3234 RPM 24.40v 1.46A 800gr Load 47.3% Eff
2662 RPM 24.29v 2.12A 1350gr Load 44.5% Eff

Parallel Mode with LAB and BEMF Circuit (Pic 2 and 3))
4640 RPM 24.88v 0.65A 0gr Load
3616 RPM 24.71v 1.52A 800gr Load 50.1% Eff
2825 RPM 24.64v 2.22A 1400gr Load 47.1% Eff

Pretty much done with this particular 6 Pole rotor after achieving all the initial design goals and ready to move on to the next phase.

Pic1


Pic 2


Pic 3

[dennis foyil]

Great report ,Yaro. Looking forward to anything about the 60v results. thanks

[Yaro1776]

Yo Dennis,

Thanks for the reply and your suggestions are in mind. This particular 6 pole rotor config has been operated up to 60v in series mode - it is a bit of a monster at this voltage and it yields comparable efficiencies, but the limits of the torque testing apparatus are pushed. In parallel mode the apparent voltage and amperage are magnified by a factor of two or so

In parallel mode the highest voltage has been limited by the LAB's at 24 volts. The BEMF circuit in its present config has its voltage limitations. I can use the 60v power supply but the motor operation is not as smooth as with the LAB's. In the past the parallel coil circuit has been pushed to 36v with comparable results, but the coils start to overheat due to the higher amperage draw. There is a give and take here that imposes limitations inherent to the coil design parameters.

I will give it a shot this coming week using the power supply to jack up the voltage in parallel mode. Better yet, build your own ZFM and play to your heart's satisfaction.

Later,
Yaro

[Yaro1776]

ZFM Video - 6 Pole in Parallel

To finish the documentation on the parallel mode of operation for this rotor (2"Lx1/2"Wx1/2"T) the following video was completed to flesh out the information.

The setup was the normal arrangement with the exception of the individual coils being wired in parallel and then connected in series. Parallel mode compresses the operation by reducing the voltage required to drive a load at a desired low usable RPM. Very useful for the lower RPM range in that it can be a direct drive type of arrangement for transmitting power; powered either through a solar panel or LAB. The nominal power efficiency throughout the test was 50%+/-.

RPM	Volts	Amps	Load gr	%Eff
4182	24.08	0.57	0	0.0
3350	24.42	1.37	800	52.1
2550	24.98	2.02	1400	46.1
5186	30.18	0.69	0	0.0
3343	30.03	2.03	1400	49.5
6014	36.03	0.77	0	0.0
4167	35.99	1.99	1400	52.7

I may add some more info to this post later, but ready to move on...

Yaro Happy Valentines Day

[John_Koorn]

Great to see you're still at it Yaro

[Yaro1776]

Great to see you're still at it Yaro

Thanks for the encouragement John!

Not done with this motor as yet and am preparing another rotor design for the 6 Pole. I expect to put this modification into testing shortly with the goal being an efficiency of 60% under load while staying within the dimensional constraints of the existing motor body and three coll config for the 6 Pole.

The virtual pole concept for the air core coils is still in play...
Yaro

[Yaro1776]

ZFM Video 20.4 6 Pole

So the next rotor configuration was designed to further explore the displaced magnetic poles of the coil. The static arc width of the individual coil poles was set to 56⁰ by increasing the width of the Neo's to 0.75", unfortunately the Neo lengths and thicknesses available for this width are very limited. As a compromise the length was set at 1.5", a bit shorter than the rotor length of 2", with a coil to Neo gap of 0.130" +/-. Not ideal but useful nevertheless for exploring.

So the coil arc dimension is 45⁰ and the Neo's are separated by an arc of 60⁰. So there remains a bit of play here that needs to be considered. That is the fun part and the most tedious to explore. For this config the overall length of the coil power on period is 49⁰ taken directly from the screen shot. This value can be expanded or contracted a bit by the positioning of the reed mount with respect to the timing rotor face. The start of the power-on pulse (advance) can be controlled by rotating the reed mount cylinder.

Since the coil's magnetic poles function in a simultaneous push/pull manner on the 6 pole rotor the coil magnetic pole arc value becomes very important. One can design for the static configuration, but does this hold true dynamic operation? Good question...

Anyway, for the video the ZFM was operated at 48v to demonstrate the major point - BEMF value and its influence. By nature, adding more Neo's and coils for a given design will increase the BEMF. For this config the peak BEMF is typically ~15% higher than the input voltage at unloaded speeds. Reducing the number of rotor poles and motor coils will reduce the BEMF value for a given RPM. The reverse is true also.

The load for the video was 1400 gr. yielding 25.5 watts or 18.8 ft lbs/sec of useful power at an efficiency of 46-47%.

Changing the wiring from series to parallel mode at 24v yields nearly identical results.

Yaro

[Yaro1776]

ZFM 6 Pole with Stacked Neo's

The testing program for this season has come to completion with the 6 Pole rotor outfitted with one set of six 2"x0.75"x0.375" Neo's stacked with 1.5"x0.75"x0.188" Neo's using the Loctite AA 326 magnet adhesive. The Neo's were first stacked and cured, then mounted very carefully on the rotor taking into account the nearly 80# pull force. Fortunately the Al rotor is non magnetic, however the adjoining magnets make this a somewhat tricky operation.



The rotor was installed in the 3 coil ZFM assembly with the coil to Neo gap adjusted to 1/16" - tight. The ZFM was then tuned to the appropriate dwell and advance, then cranked up and tested both in serial and parallel mode. The longer length and greater magnetic pull force along with the tighter gap over the previous configuration did reduce the RPM, but improved the overall efficiency. The most reasonable configuration that yielded both output power and efficiency was in the 30 volt parallel mode. The virtual coil poles for this Neo arrangement were very similar to the prior posts coming in about 55 degrees - not ideal but close to. So lets take a look at the run data:

RPM	Load(gr)	Output(w)	Volts	Amps	Input(w)	Eff%
4026	0	0.00	30.28	0.60	18.17	0.00
3406	1020	22.61	30.66	1.39	42.62	53.06
3010	1630	31.94	30.64	2.03	62.20	51.34
2917	1825	34.65	30.72	2.16	66.36	52.22
2942	1760	33.70	30.66	2.14	65.61	51.37
3402	960	21.26	30.31	1.40	42.43	50.10

So the modifications demonstrate that improvements can be gained in performance. Further improvements can be gained by several methods: 1) Virtual coil arc of nearly 60 degrees, 2) Improving the actual coil dimensions to a tighter tolerance for consistency and 3) Better selection of Neo sizing.

A quick expanded look at the oscope shot at high load below



One will note how quickly the amperage (blue trace) returns to a zero value when the power is cycled off and the how rapidly the voltage rises on power-up - a definite characteristic of the air coil. So at this stage of experimentation all the goals were achieved, with the exception of the virtual coil arc. This particular ZFM configuration should be able to achieve 60% efficiency or more with the proper build techniques and tuning.

For the next phase of evolution there are experiments planned to work with the coil wiring using a multifilar approach. A recently conducted experiment using the current assembly yielded preliminary results demonstrating that this can be a very worthwhile direction. More to come this late summer barring any disruptions in the material supply chain. One can only hope!

Thank you for your attention, stay healthy and enjoy the summer,
Yaro