Traction Motor

I wont answer the "power to weight ratio". Motors don't make power, they consume it. You'll find the best motors for the job are brushless DC with plenty of rare earth magnets in them. They aren't cheap.

Your statement "Motors don't make power, they consume it." does not make any sense !!

You mean motor cannot be rated by power ! are you ok?

rated by torque -- output --

I think what the OP wanted to know was the effective HP output vs the weight of the motor.Which weighs less for the same developed horsepower.Efficiency is another matter; electrical power input vs mechanical power out.

'Course I could be wrong....

What size?

For EV, 50 to 100 horse.

Traction Motors generally have HP as good as 1420. We used two DC Motors for goods train in 1978. Single phase Catenary 25kv ac voltage is stepped down to 2kv inside the train by transformer and fed to reversible thyristor power amplifier. Power from this power amplifier is fed to 1420HP motor having separately excitation(field) winding.

During starting of train, it need high torque so obtained by maintaining same amount of current in armature winding and filed winding of the motor as if it would acts as Series Motor( series motor is very good for high starting torque). Once it picks the speed it does need high torque but need small torque to over come the fictional losses on the track then Armature winding and field winding currents don't maintained same so it would work as if a shunt motor(shunt motor is good for speed control).

In olden days induction motors were used with low frequency around 16.5Hz for good speed control.

Therefore there is no relation between power and weight.

Now a days Linear induction motors are being used to go high speed trains as good as 300km/hr to 400km/hr and trying to use in this field super conductor which has very high current density due to very low resistance for same size of copper conductor.

Thank you for your reply.

There is certainly relation between power and weight. It is a crucial consideration point for EV.

For efficiency and small size a permanantmagnet synchronous motor will be the first choice. The separate inverter will effectively make it a brushless DC machine.

If you are looking for a high efficiency electric motor you might try these people;

http://www.solarnavigator.net/lynch_motor_sales.htm

They claim efficiency's around 90% which would be pretty amazing if true.

We always installed a motor with more max torque than we needed to prevent overheating and to lifespan

I would like to add some more information on the same subject. The question is thrown on the forum to integrate a variable from the limit "a" to "b". Since you will get infinity answers as "a & "b" can take infinity values.

If question should have definite parameters then answer will be within 90% to 100%.

I want to clarify information on motor & Generator as follows:

1. Any rotating AC or DC motor consume power from network and its power will be designated as +Watts(+ve). Except case; generates power for small duration when converts kinetic energy of the connected load into electric energy.

2. Any rotating AC or DC motor generally or supply power to network and its power will be designated as -Watts(-ve).

3. There will be no ratio exist between power to weight. Ratio varies on the input Voltage & power rating of the motor.

4. Selection of motor shall be based on the cooling or ambient temperature and what is the expected torque or load on it otherwise you are draining the money without any use.

I think you are the third post to say there is no relationship between power and weight.

It may well be that power output is not the most significant factor in choosing a motor for an Electric Vehicle, but for a given design, a motor having greater power output capability is surely going to have more weight than one with lower output capability.

The above sentence could be repeated replacing 'power' with 'torque'.

Perhaps the wording of the OP's question is less than perfect, but to me, the intent is quite clear: he wants to know which design of motor will carry his EV the greatest distance at a reasonable speed. Obviously, that means he needs a motor that is not very heavy, yet still has adequate torque/power capabilities.

GA, thx.

GA

http://www.eetimes.com/design/automotive-design/4215581/Electric-hub-motor-improves-EV-range--Part-1-Technology-basics

good link, thank you.