Examples

This page shows motor and generator examples based on the TFM1 model. The calculations are based on the results from the experiments and measurements and should be considered as initial estimates only.

It is interesting to see how increasing the operational frequency through increasing the number of poles significantly improves the motor efficiency and lowers the weight.

Motor diameter

The examples selected has been limited to a diameter up to around 0.5 meter. The reason is that the air gap between the stator and the rotor has to be increased with higher diameters. The air gap range from 0.2 mm to around 0.1 % of the stator diameter (outrunner) or rotor diameter (inrunner).

Regenerative braking

The motors can also be used as generators for regenerative braking. The maximum braking capabilities are much higher than the rated power for some of the examples. Braking with minimum loss can be achieved up to the rated power.

Total weight calculation

A motor will consist of core parts like magnets, copper windings and magnetic conductor elements (silicon steel). In addition comes parts for cooling and structure elements including housing and a shaft. The weight of the core components has been calculated by a configuration program. The weight of the remaining parts is assumed to be roughly the same as the core parts. The total weight stated is thus the double of the core parts. A real motor will have a different total weight.

The weight is calculated for silicon steel. The weight when using iron powder is slightly different.

Parameters:

The magnet type used is either ceramic type 8 (Cer8) or a strong neodymium grade (N52).

The number of poles is stated for each phase multiplied with the number of phases.

The Prototype

*
Maximum power 0.039 kW
Torque 0.246 Nm
Loss (resistive/copper) 2.7 %
Loss (flux/iron) 8.1 %
Type of magnets N52
Diameter 0.07 m
Length 0.02 m
Number of poles 24
Rotation 1500 RPM
Frequency 300 Hz
Copper weight 0.03 kg
Silicon steel weight 0.09 kg
Magnet weight 0.04 kg
Estimated total weight 0.322 kg

Cars

TFM1 motors will be an excellent choice for electric cars. The fixed gear (10:1) used today can be removed for lower price, less noise and improved efficiency. The low weight makes 4-wheel drive attractive. The motors can also be used as powerful generators and thus providing very good braking capabilities with energy regeneration.

TFM1 examples A B C
Maximum power 110 220 40 kW
Torque 910 1300 240 Nm
Loss (resistive/copper) 2.3 2.2 4.5 %
Loss (flux/iron) 0.2 0.2 0.2 %
Type of magnets Cer8 Cer8 Cer8
Diameter 0.36 0.36 0.25 m
Length 0.16 0.17 0.08 m
Number of poles 74 * 3 74 * 3 74 * 3
Rotation 1200 1600 1600 RPM
Frequency 750 1000 1000 Hz
Copper weight 2.3 2.4 1.6 kg
Silicon steel weight 5.2 5.8 1.0 kg
Magnet weight 5.5 6.6 0.7 kg
Estimated total weight 26 30 7 kg

Today’s typical car electric motor may weight 50 kg and produce 110 kW at a rated speed of 135 km/h. A total of 78 poles means 26 poles for each phase (3- phase) and a basic frequency of 13 times the rotational speed. A gear of 10:1 means that the motor itself runs at 12000 RPM using an electric frequency of 2600 Hz at rated speed.

Scooters and Motorcycles

Using a transverse flux motor for scooter and motorcycle direct drive hub motors will be an excellent choice. The direct drive hub motor configuration provides very good braking capabilities with energy regeneration. Using a hub motor on both wheels is also an option with good properties for acceleration and braking.

TFM1 examples A B
Maximum power 3.1 80 kW
Torque 47 665 Nm
Loss (resistive/copper) 1.7 1.6 %
Loss (flux/iron) 0.6 0.2 %
Type of magnets Cer8 Cer8
Diameter 0.19 0.22 m
Length 0.08 0.14 m
Number of poles 94 * 3 104 * 3
Rotation 630 1150 RPM
Frequency 500 1000 Hz
Copper weight 0.98 2.1 kg
Silicon steel weight 0.64 2.2 kg
Magnet weight 0.45 2.1 kg
Estimated total weight 4.1 13 kg

Bicycles

Transverse flux motors can be used for direct drive bicycle hub motors. The motor provides very good braking capabilities with energy regeneration. Using a wheel with half the diameter and doubling the operating frequency will reduce the motor weight.

TFM1 examples A B C
Maximum power 0.26 1.9 0.26 [kW]
Torque 13.4 100 6.7 [Nm]
Loss (resistive/copper) 3.6 5.5 2.2 %
Loss (flux/iron) 1.3 0.1 2.2 %
Type of magnets Cer8 Cer8 Cer8
Diameter 0.25 0.26 0.25 [m]
Length 0.05 0.07 0.04 [m]
Number of poles 128 * 3 128 * 3 128 * 3
Rotation 187 187 374 [RPM]
Frequency 200 200 400 [Hz]
Copper weight 0.5 0.7 0.3 [kg]
Silicon steel weight 0.4 0.7 0.3 [kg]
Magnet weight 0.2 0.9 0.1 [kg]
Estimated total weight 2.2 4.5 1.4 [kg]

Aircraft

TFM1 examples A B
Maximum power 85 260 kW
Torque 370 1130 Nm
Loss (resistive/copper) 2.5 2.1 %
Loss (flux/iron) 0.2 0.2 %
Type of magnets Cer8 Cer8
Diameter 0.22 0.27 m
Length 0.13 0.18 m
Number of poles 54 * 3 54 * 3
Rotation 2200 2200 RPM
Frequency 1000 1000 Hz
Copper weight 1.6 2.5 kg
Silicon steel weight 2.0 4.6 kg
Magnet weight 1.0 5.9 kg
Estimated total weight 11 26 kg

Small windmills

For small windmill (< 20 kW) transverse flux generators will offer an attractive gearless solution.

The TFM1 model can provide much high efficiency using ceramic magnets only. Using an output frequency of 200-400 Hz instead of 50 Hz reduces the weight significantly.

TFM1 examples A B C
Maximum power 0.6 1.1 6.1 kW
Torque 9.6 21.4 815 Nm
Loss (resistive/copper) 2.4 2.2 1.1 %
Loss (flux/iron) 1.1 1.2 0.7 %
Type of magnets Cer8 Cer8 Cer8
Diameter 0.15 0.19 0.55 m
Length 0.06 0.07 0.13 m
Number of poles 78 * 3 96 * 3 334 * 3
Rotation 608 500 72 RPM
Frequency 400 400 200 Hz
Copper weight 0.35 0.38 5.6 kg
Silicon steel weight 0.30 0.55 5.1 kg
Magnet weight 0.14 0.37 6.3 kg
Estimated total weight 1.6 2.6 34 kg

Example generators found on the Internet:
a) 200 W generator, 600 RPM, 3,2 kg
b) 500 W generator, 450 RPM, 4,6 kg
c) 600 W generator, 600 RPM, 7.5 kg
d) 1.1 kW, 500 RPM, 79 % efficiency, 13 kg
e) 5 kW, >85% efficiency, neodymium magnets, 165 kg

Medium windmills

For medium size windmills (around 100 kW) it is fully possible to use a gearless solution. The shown example demonstrates the potential. Using a high output frequency (around 200 Hz) is especially attractive. In this case an AC-AC converter has to be used to convert the output to the grid frequency. The windmill can then run at the optimal speed for higher output power over an extended range of wind speeds. Note that the diameter of the generator should normally have been 3 times larger, but a certain “reconfiguration” allows the diameter to be reduced and the length extended instead. The generator efficiency is near 98% which is very good.

TFM1 example A
Maximum power 100 kW
Torque 12400 Nm
Loss (resistive/copper) 1.9 %
Loss (flux/iron) 0.2 %
Type of magnets Cer8
Diameter 0.55 m
Length 0.5 m
Number of poles 314 * 3
Rotation 76 RPM
Frequency 200 Hz
Copper weight 33 kg
Silicon steel weight 26 kg
Magnet weight 49 kg
Estimated total weight 216 kg

Typical generators found on the Internet have higher weight and lower efficiency compared to the TFM1 example:
a) 100 kW direct drive wind generator, 4000 kg, >92% efficient
b) 22.9 kW, 80 RPM, 84 % efficient, 193 kg

Large windmills

For large windmills (> 1 MW) it becomes harder to avoid the fixed gear. However, the number of gear stages can be reduced compared to traditional solutions. This has advantages related to lower price and reduced maintenance.

Industry

Transverse flux motors has proved successful for industry applications.

ELECTRIC TORQUE MACHINES has developed transverse flux machines. For example, the ETM M100 (430 W, 3.6 kg, 4.6 Nm, 900 RPM, 90 % efficient).
http://etmpower.com/
http://etmpower.com/learn-more/technical-information/

 
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