Variable speed drive for asynchronous motor

[toto65]

Is that three-phase is a necessary condition to vary the power of an asynchronous motor?

No

For this, transformers (called auto-transformers) controlled by servomotor or chopping systems by triacs / thyristors (called electronic speed regulators) are used.

Manual and automatic voltage regulators.

The vast majority of these systems only equip small fans. They allow adjustment from 0 to 100%.

Please note, however, that the motor must initially be designed to operate at variable voltage. In fact on standard motors, the drop in voltage results in an increase in the current which is inadmissible for the motor.

The phase chopping adjustment system creates harmonics which not only disturb the operation of the motor, but pollute the distribution network. Adjustment by transformer does not, however, create a harmonic.

Price is the main advantage of these regulation systems.

Transformer systems allow adjustment of the speed in stages, while phase chopping systems allow continuous progressive adjustment. However, care must be taken not to start on a low speed at the risk of destroying the engine.
The energy performance of these systems is not good

Frequency converters

The most favorable speed regulation from the energy consumption point of view is that obtained with a frequency converter.

source:
http://www-energie.arch.ucl.ac.be/CDRom ... tventi.htm
purchase:
http://www.technic-achat.com/boutique/f ... e=59&num=1
Documents:
http://www.technic-achat.com/boutique/p ... m_actus=10

[tome]

Exact!
Chritophe
Do you have a condo in your engine?
Otherwise there is this:

http://www.directindustry.fr/prod/itt-f ... 72247.html

[Christophe]

That someone explains why the module triac does not work and what it works then ...

not me anyway ! but I think toto did it

Documents:
http://www.technic-achat.com/boutique/p ... um_actus=1

There is something that I do not capture in the table, the first 8 columns have a reference - X1 which means output in mono while on the output voltage line there is the symbol "3O" which means 3 sentences no?

Ah no, this 1 corresponds to the supply voltage ... everything goes well in three-phase so not good ...

Do you have a condo in your engine?

Yes there is one but I don't know if it's a start-up or working condo. André had explained the nuance but I forgot

[tigrou_838]

hello christophe,
If I remember correctly you have a self-draining solar installation, and I think that you should not vary the power of your pump, you need all the power to raise the water to the top of the roof so that your solar system can rotate properly.

I wonder if it is a good idea to want to regulate the power of the pump, or just be after having primed the solar system by the pump, regulate a little, I think it would be necessary to try with a dimmer connected to the maximum power and then see by reducing.

tiggo.

[jonule]

Yes there is one but I don't know if it's a start-up or working condo. André had explained the nuance but I forgot

Ah well it's simple: there is one that is used for starting, and the other for operation!
if you don't need me i'm not there!

[Christophe]

Relaunch of the subject with these measurements made this morning with unexpected results: https://www.econologie.com/forums/abaisser-l ... 11126.html

We decrease the power (and the RPM speed) of an asynchronous motor by varying the supply voltage (or what I have is not an asynchronous motor?!?!?) But if manufacturers offer frequency converters is that there must be a good reason right? (amperage too high under a certain voltage?)

[dedeleco]

The big problem is the starting torque which tumbles much faster than the voltage, the engine starts charging only with a fairly high voltage (very clear with lawn mower) and after starting, you have to lower the voltage to decrease the power, rotational speed and flow rate of the circulator.

So you need an electronic circuit that lowers the voltage once started automatically !!

The frequency variation ensures a high starting torque, starting at almost zero frequency which adjusts to the rotation speed fixed by the frequency !!! The intensity must also be controlled.

[Christophe]

Yes it may be the reason (among other things) of the frequency variation solution rather than voltage used by the "pros".

For me, no problem. Already thought and solved: a timed relay does this without any worries!

Power supply at 230 V AC direct for X seconds and switching to rheostat set to YV AC thereafter.

Much less expensive solution than a frequency converter (see above)

Empty on a 700W motor we have this:



Restart voltage: 35 VAC
Stop voltage (by lowering the voltage from 230 to 0V): 20 VAC

[dirk pitt]

on a small pump, the motor may not be asynchronous but what is called a universal motor with coals. in this case, the voltage variation lowers the speed. that's what there is on all portable drills.

[Christophe]

Well, everything suggests that it is an asynchronous motor (capacitor, triangle / star wiring possible in three-phase version ...) ...

See also Macro's note here: https://www.econologie.com/forums/post212445.html#212445

I am trying to connect the 500 VA to my solar pump this AM