1892

Item 1892

OTHER: Electrical - Motor - Stator - Wire

General:

Wire Gauge and Current Limits. "The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire."See: Access database - Motor - Table - Wire Gauge & Form - Stator Winding.

Compare the vales for wire size on Why are Fuses and Solenoid Disconnects So Important in EV's? with the values for cabinets on Wire Gage and Current Limits. The cabinet values are 3 times more conservative than those in the EV article.

The wire I bought to test the 'phaseless motor idea' was 1 lbs of 19 AWG. ~ 0.0359 " dia.

Have bought 1 lb of 24 AWG for Rick to test to destruction.

Lee's Electronics carries 30 AWG 14 AWG (0.0641" dia.) to 30 AWG (0.01" dia.) in stock

4.2.10 Armature Line Current Density. [Source ~ PMMT p.132]

4.2.11 Armature Winding Current Density. [Source ~ PMMT p.133]

Note re Litz wire: The density is based on the area of the wire(s) and not on the circumference of the wire(s).

Figure 4.6

4.2.12 Armature Winding Resistance. [Source ~ PMMT p.133]

4.2.13 Armature Winding Inductance. [Source ~ PMMT p.134]

Copper Vs. Silver Wire Conductivity:

It might be interesting to compare the conductivity of silver to that of copper. The reasons being that the helicopter is arguably the most inefficient vehicle. Therefore, making the motor more efficient (less heat generated) and proportionately reducing the weight of the battery may offset the higher cost of silver.

Material:	Conductivity:	Resistivity:	Density:	R/D ratio:	Cost:
Copper:	59 x 10^6 siemens/meter	26.5 ρ (nΩ m)	8.96 g/cm^3	2.958	$3.38/lb
Silver:	63 x 10^6 siemens/meter	17.1 ρ (nΩ m)	10.49 g/cm^3	1.630	$513.92/lb
Aluminum:		15.9 ρ (nΩ m)	2.70 g/cm^3	5.889	$1.15/lb

Reference; The weight of copper on the original F & P motor for the Electrotor-SloMo is 1.137 Kg.

What about silver coating only????

Electrical Conductivity and Resistivity

For listing of material electric conductivity see DESIGN: Electrotor-Plus ~ MRGA

Litz wire:

Litz wire calculator:

Definition: http://en.wikipedia.org/wiki/Litz_wire

Eddy current loss is controllable with stranded Litz wire, leading to an efficiency greater than 97%. ~ http://www.tip.csiro.au/Machines/papers/iwscem/index.html

Some useful information on Litz wire - charts show various strand quantities for different operating frequencies, O.D. of wire, guage, wt. resistance/1000 ft etc Saved in removable E-drive as Round_Litz_2B72407.pdf.

"The weaving or twisting pattern of litz wire is designed so individual wires will reside for short intervals on the outside of cable and for short intervals on the inside of the cable. This allows the interior of the litz wire to contribute to the cable's conductivity."

This appears to be the way to go. See; Ironless wheel motor for a direct drive vehicle application. http://www.itee.uq.edu.au/~walkerg/publications/2003/114%20Greaves%20full%20paper.pdf Have hard copy

Would the dense packing of the Litz wire combined with a reduced gap, due to the straight sides of the wire be significant. Particularly in removing the need for a laminated or soft magnetic Composite (SMC)?

Litz (multi-strand wire):

AWG	Diameter:	Area:	Area Ratio:	Resistance / 1000 ft:		Circumference:	Circumference Ratio:
32	0.008"	0.000050sq-in	826.9	164.1 ohms	826.9 * 0.197 = 162.9 ohms	0.024	30
3	0.2294"	0.04135 sq-in	to 1	0.197 ohms	826.9 * 0.197 = 162.9 ohms	.72097	to 1

Neither of the above two means of tackling R appear to change the heat loss.

Perhaps only the volt - amp ratio is the only one

Skin Effect:

I'm wondering if Litz wire is advantageous.

Alternating Current frequency:

The frequency of the reversing polarity of the DC trapezoidal current will be RPM x pole-pair count / 60.
The rotor speed of the SloMo is roughly 700 RPM. The pole-pair count is 24. Therefore 700 x 24 = 16,000 per minute = 280 Hz.
For reference: The rotor speed of the Plettenberg is roughly 6,000 RPM. The pole-pair count is 10. Therefore 6,000 x 10 = 60,000 per minute = 1KHz.

Pulse Width Modulated frequency:

IGBTs have been the preferred device under these conditions: Low frequency (<20kHz), etc.
MOSFETs are preferred in: High frequency applications (>200kHz), etc."

Litz wire mitigates skin effect for frequencies between a few Kilohertz to about one Megahertz.

Which is the 'frequency' of interest;

1/ The alternating current frequency (280Hz), or

2/ the pulse width modulated frequency (+/- 27KHz)?

Random Note:

"Compared with a round wire, such a solution, called ‘Litz wire’, has a lower AC resistance. However, its DC resistance is higher and depends on the fill factor."

See; DESIGN: Electrotor-SloMo ~ Motor - Axial Flux - Stator - Wire

Supplier of Litz wire:

E-Bay:

http://shop.ebay.fr/?_from=R40&_trk...-All-Categories

Electrically Connecting the Ends of Litz wire:

Litz wire soldering:

Professional method:

Soldering Litz Wire

Square Shaped Wire:

Inside the HVH™ Hybrid Motor Have hard copy.

Carbon Nanotube:

Definition: http://en.wikipedia.org/wiki/Carbon_nanotubes#Electrical

Thoughts:

Wire Coating: If the coating on the wire is approximately the same thickness for all AWG then with coils of small wires the coating will be taking up a greater proportion of the space that is being used for the wrapped coil.

Outside Web Pages:

Skin Effect: Since the PWM will be at a high frequency also see Litz Wire.

Last Revised: November 29, 2011