Universal motor alternator or current generator

[Christophe]

Details concerning the speeds:

a) The original gear ratio (per belt) is 16 to 1.
b) The paddle wheel should rotate (= stream flow speed) between 50 and 100 rpm.

In the best of the cases I thus have 1600 RPM without having to make a 2nd multiplication.

Also, the maximum torque the screwdriver which turns at 1200 rpm is 23Nm or a maximum power of: 1200 * 2Pi / 60 * 23 = 2900 W (not long) so it has ample "reserve" within the framework of these tests.

[chatelot16]

for an alternator or a high efficiency engine the power in engine or alternator is almost the same, and the excitation power is derisory

but the universsel motor is made to be ultra light no matter the performance

a 500W electric motor with a yield of 50% will make 250w mechanical: in dynamo it will transform 250W mechanical into 125w electric: not glorious ...

the yield is not necessarily as bad as 50% but to improve it must be used at an even lower power

[Christophe]

1) I don't quite understand your last sentence: is it related to the excitation curve?

2) Well, speaking of performance, on this famous engine on which I drew all the curves, there is a plate which indicates:

- 225W, 2A
- 85W, 3,5A

It would establish a return.

Problem: I do not know the voltage (or the RPM) for these 2 regimes ...

With an efficiency of 70% and cos phi of 1 (hum?), We can assume the following voltages (order of magnitude):

- 225 / (0.7 * 2) = 160 V
- 85 / (0.7 * 3,5) = 35 V

If the efficiency is 50% or even less (which I think more and more) then as much as I use an automotive alternator right?

In any case I would have had fun and learned with these universal motors and I could always use one as ... tachometer thanks to the inductive sensor they have on the axis and which makes a beautiful sinusoid

Subsidiary question: if I want to run the motor to measure the voltages / current precisely, what must I put as a signal on the brushes and what on the stator?

[Christophe]

By the way, this:

original method: make an electronic excitation generator sinusoidal 50 Hz and we recover by the coal of the power 50 Hz even if the speed of rotation is variable

I've never seen use this principle but it has to serve pourais 50Hz an alternator with a turbine that spins very quickly

On mine it does not work: when I put 12V AC (ferric tranfo therefore 50Hz) on the excitement, it gives me an electric cacophony ....

[Other]

Hello

By the way, this:

original method: make an electronic excitation generator sinusoidal 50 Hz and we recover by the coal of the power 50 Hz even if the speed of rotation is variable

I've never seen use this principle but it has to serve pourais 50Hz an alternator with a turbine that spins very quickly

On mine it does not work: when I put 12V AC (ferric tranfo therefore 50Hz) on the excitement, it gives me an electric cacophony ....

Theoretically it could work, but in practice a generator not compensated for a setting of brushes at the neutral point which is according to the load and the direction of rotation of the generator so by involving an AC excitation there is a risk of having good on a alterance and mediocre on the other more at 50hz there is far too much inertia in the Feild.

Subsidiary question: if I want to run the motor to measure the voltages / current precisely, what must I put as a signal on the brushes and what on the stator?

The tachometers on the old engine were simple shunt generators, the old DC engines took their reference on a small generator at the end of the shaft which controlled the (Loop)
These generators give a voltage directly proportional to the RPM according to a certain window

Normally the excitation of a DC machine requires only little energy the new motors are permanent magnets
one cannot excite more than the saturation of the pole steel
some steel have greater permeability

Currently all these references or tachometer are simple more precise pulse generator (sometimes 600 pulses per revolution) we can even use it to make counters.

Automobile alternators, although simple, have poor performance due to their lack of magnetic carcass and electrical wiring, a bit small, at full load they need adequate ventilation the more an electric machine heats the worse it has yield
In practice, small electric devices do not perform well, whether it be a motor, a transformer, etc. It is a question of manufacturing cost.
a large 300hp motor has a good efficiency as a large transformer has an efficiency of 95% sometimes 98%
The old automobile dynamo had an acceptable return for their size always on condition of using them below their nominal power.

Andre

[Christophe]

I just reassembled the engine of the tests on the drum to try to make tests with the reduction of origin (in short the belt on the engine).

The EMPTY couple is already very important. This + the poor performance in generator (normal after all it's not done for) lead me to for the moment abandon this path. I tested the wind generator that Tigrou lent me.

Report to come in the subject "paddle wheel" ...

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