Induction motor, single phase, no capacitor to start needed.

PLEASE READ DESCRIPTION

This is a 2 pole, single phase, permanent capacitor, induction motor, 2 poles on the main winding 2 poles on the auxiliary, 127V, 3450rpm nominal.

In this clip I show that the capacitor gives the initial torque to the motor to start, and in the case of permanent capacitor, to give extra torque while functioning.

You can see that one side of the capacitor is conected to the auxiliary winding end and the other to the main winding end;
this is obviously to create the phase shift btween the auxiliary and main windings, and get a phase shift of aprox 90 electrical degrees. By closing the circuit at different poles of the capacitor you change the rotating magnetic field direction and therefore the direction of the rotor.

The main winding and the auxiliary one are circuits conected in parallel.

The common conections on single phase splitted motors is this:

The main winding is a RL circuit.
The auxiliary winding is a RCL circuit.

On the clip, I remove the capacitor making the auxiliary also an RL circuit reducing the phase shift,
two things still happen:
the auxiliary winding has still strong enough torque to start the motor, and even run it, but, since this motor does not have a centrifugal switch the auxiliary winding maintains the speed low because of the magnetic field proximity (electrical proximity in degrees) to the main one.
And since the inductive reactance of the windings is different and fixed, the motor always starts in the same direction.

It is not shown here that if I remove the capacitor and leave only one of the two windings I can start the motor by cranking it (I show that on another clip though), and it will turn in any direction at the same speed either using only the main or auxiliary winding but not both (it will have a different speed for each winding).

Category:

Education

Tags:

• Induction
• motor
• electric
• single
• phase

[u5ernam3unavailabl3]

The RL starter circuit created by using the wire will create a smaller phase angle of the magnetic field between the starter and main windings, and hence lesser torque which may cause the motor not to start when loaded as slandimore said.

[Arkthurius]

Right. One other very important thing people has not mentioned, is that in the case of permanent capacitor motors, the circuit with the capacitor not only needs to be properly shifted, but permanently connected. The capacitor circuit provides electromagnetic energy to the rotor, just like primary winding in a transf passes it to the secondary. Remember IndMot are "rotary transformers". I admit I did not thought about it when I recorded the clip. It was all about starting it without the cap.

[slandimore]

all single phase motors need a capacitor to start either left in momentory and then disconnected via a centrifugal switch or left in circuit. it is quite possible the this induction motor is able to start without a capacitor but it has no load on the shaft and by not having the cap disconnected you do not achive a full phase shife between the start and run windings thus not getting up to full speed.

[Arkthurius]

Good point. With load on the shaft the motor might not have enough power to start.

Electric motors are very interesting.

I have learnt lot of things from the comments of the people.

Thanks for posting.

[Swanny383]

It is called single phasing the motor, You will end up burning one of the windings, current goes though the roof, Just look at the wire arc, You are basicly "stalling" the motor, The cap gives it a "kick" then passes voltage onto the other windings. alowing it to spool up, you can run a 3 phase motor off of two phases, but your power will down 1/3, and you will need to use a cap to "kick" on the leg you are not using, or spin it up some other way then that "leg" will be open. (no current)

[Arkthurius]

I had not read well what you wrote. I did not know single phasing could happen on a single phase motor like this. I had heard of it only on 3-phase motors.

[CATA20034]

It has a bobin on the rotor , like dc motors aka washing machine motors ....

[exp32s]

Dear Arkthurius

Thank you so so much for all your comprehensive videos on single-phase AC motor and your explanations. Your demonstration is clear. They reinforce my understanding of the operation of AC motor.

i would like to let you know i am very grateful for your efforts to upload those helpful videos : )

With appreciations

[coldarc]

ac motors works without capacitors. the only advantage with capacitors

is that there is no need for hand crank start and that they give out more mechanical power than the currents supplied by the input. the capacitor is generating extra power

for free. this is because the magnetic field is out of phase between rotor and stator.

the capacitor generate extra energy by increasing the phase differential between rotor and stator.

[dish125db]

sounds like the starting phase is only working without the cap......

[ososordo]

el motor monofasico tiene 2 clases de bobina 1) TRABAJO: que es la que hace toda la potencia .- 2) ARRANQUE: es la que solo hace el primer giro de ayuda , ya sea izquierda o derecha .- el tema es que cuando se deja funcionando sin capacitor , la bobina de arranque se quema , ya que el bobinado del ARRANQUE se hace con menos vueltas que la de TRABAJO

[isovolt1]

you can see a better replacement at web page isovolt

[domyaska]

grazieee ..thanks a lot!! from italy

[slandimore]

i agree i have fitted and fault found on the following motor control systems single phase cap start single phase cap start cap run etc 3 phase star delta 7.5kw to 320kw 3 phase direct on line 3 phase inverter controlled 3 phase soft start 3 phase multi speed tapped windings 3 phase multi speed duel wound 3 phase resistance start single phase series parrell 480v series parrell so any body got any questions i would be more than happy to answer then if i can....

[tommyjay83]

Not at all. If you have a 230v single phase power supply you can buy either a Toshiba VF-S11 or VF-NC1 variable frequency drive.  You can single phase the input of the drive and get three phase power out of it to feed your motor. Just de-rate the VFD by half (ie. powering a 5HP motor, use a 10HP VFD)