CSIR Type Motor to CSCR Motor Conversion

Why would any sane person want to?

What you are describing is like what you get if the centrifugal switch inside the motor (or external start relay) fails and permanently remains in start config ie cap always in series.

Why you want to do this or what benefit you hope to achieve you have not mentioned.

You could find out yourself with some simple experimentation. A second cap in series with the run wire (just like the start wire has) will result in a series cap start/series cap run motor. (not to be confused with regular cap-start/cap-run motors where the run cap is in parallel not series)

Or you could have a Google.

Coz i need to improve the power factor ,as csir type motor has low power factor as compare to cscr type.

if low value cap is permanently connected parallel to centrifugal switch, and rest the connections and circuits remains same then what happens

Are you sure you mean parallel with the switch?

Googling will teach you more faster than a game of 100 questions.

in short how to improve p.f of csir type motor

Theoretically yes, but is the start field of a type that will handle continuous operation?

Do you have a cap rated for continuous usage?

Are the motor bearings designed for the extra torque that should be developed?

Is the machinery it drives also able to handle the extra torque?

Is there going to be a speed change of the motor? Less slip? (I am guessing here?)

Can you access the centrifugal switch to disable it?

Will the motor be able to dissipate any extra heat developed properly?

I am sure that I haven't covered it all either......

if we permanetly add low capacitor to csir motor what happens.

Nothing good as the motor is not designed for it, why are you trying?

will it improve some power factor??

Not safely, if the motor even works. Adding a capacitor in series with the start winding across the centrifugal switch will alter the running characteristics significantly, and not in a good way so don't!

Try the proper way by either adding external capacitors, adding a variable speed drive or properly loading the motor to begin with

http://en.wikipedia.org/wiki/Induction_motor

Since you want to do it anyway, what size motor are you talking about what is it being used for?

Design1,

In the 1980's an offshoot of a NASA design was marketed extensively in the USA, called a "power factor controller", with the claim of energy conservation. It was specifically designed for the type of motor you are working with, and was wired to the line feeding the equipment. This device did the job it claimed, and I would recommend you check around for that design (public property, not patentable).

--JMM

The old Watt Wizard(TM) (or whatever it is called now days).

A variable speed drive is also a (more expensive but flexible potential) option.

Despite all the draconian warnings, for small motors there's nothing inherently wrong with adding a run capacitor, if anything the motor will have greater starting torque and be smoother running.

The trick is to use the right type, size, and rating for the run cap, remember, you can use run caps as start caps but not vice versa, so don't look at the existing start cap and duplicate it.

btw- if this is a small motor the gain in efficiency and pf probably won't show up in your electric bill unless this is a 7x24x365 operation, but if you think that improving pf is going to somehow lower the energy consumed by your motor, you're wrong. The energy consumed is a function of the mechanical load, the motor just supplies the equivalent electrical power presented by the mechanical load. It's a load follower, not a load controller.

RAMConsult,

Not entirely correct about a capacitor and energy bills. The capacitor supplies the reactive power required for the motor to operate. Properly sized, the power factor will be corrected to a number very close to 1.0 (such as 0.96). This does lower the line current (sometimes requiring a change in running current protection if the capacitor is on the motor side of the contactor). If the power factor is fairly high before adding a capacitor then the savings of energy is fairly small and may not be noticed--something you state correctly.

--John M.