Speed Changing Of Single Phase Motor

yes

Yes, it is.

Yes. The easiest way is to turn it off.

That's logical and spot on topic!

Vary the frequency.

"There are four basic groups of speed control that are often used with fans and blowers. The simplest is the variable speed motor. The remaining three groups are passive device speed controls, solidstate controls, and mechanical devices. Each way is unique and is used throughout the industry but you must be careful when trying to match any speed control with a motor. Whatever the application may be, be sure to check with the motor manufacturer to be assured their speed control criteria is being met because some motor manufacturers will void their warranty if the motor is not approved for speed control. Also, be aware of all safety issues such as thermal overload protection as this needs to be part of the speed control system. There is often a substantial amount of heat generated at the motor when speed controllers are used. To prevent accidents or damage it is always recommended that a thermal overload protector either be part of the motor or of the controller itself."

horsepower (HP) = torque (lb.ft) x speed (rpm)/ 5250 (constant)

speed (RPM) = 120 x motor supply frequency /number of motor poles

Additional info on methods....

http://www.aerovent.com/docs/fan-engineering-topics/speed-control-for-fractional-hp-motors---fe-1000.pdf?Status=Master

but is it possible through any device/any special type of wiring ...any circuit diagram would helpful..

You can see from the answers your getting that single phase; Capacitor Start, Capacitor Run (CSCR) or Capacitor Start, Induction Run (CSIR) motors do not have a simple method of speed control. And if you were to have some sort of 1 phase variable frequency inverter, your torque output and speed range would be very limited.

If you are really wanting a wide speed and torque range, change to a 3ph motor and use a VSD/VFD controller. If your talking fractional (under 750 watt) motor size, this is inexpensive for both the motor and VFD.

Another option is a DC motor and amplifier to drive it.

What is your motor application? Your lack of useful specifications is why your getting the answers you are (not).

Sure. Overload it. That'll slow it down!

Yes, put a Variac on the supply line. Lower the voltage till it runs at the speed you want or if it catches fire or explodes unplug it. Raise the voltage till it reaches the speed you want or if it catches on fire or explodes unplug it. Prior to this make sure insurance is paid up.

Another method is to use a pulley/v-belt drive and change the pulleys till you get the speed you want. Calculating the diameters is faster and probably cheaper before you buying a arm full of pulleys and belts.

Good Luck, Old Salt

NO!

The key here is your qualifier of "CSIR or CSCR induction motor". When you use an electronic means to attempt to vary the speed, the centrifugal switch used to remove the capacitor from the starting circuit will re-engage when the speed drops, putting the capacitor and/or start winding back in the circuit. In these design, the capacitor is either NOT rated for continuous use, or is raw to the line voltage. In that second case, the exposure to whatever you use to vary the voltage and frequency (in order to change speed without loss of torque), will either damage the capacitor or be damaged by the rapid charging current change (dI/dt) of the capacitor. So it becomes a race to see which one fails faster.

There are only two types of single phase motors that can use speed control; Permenent Split Capacitor (PSC) or Shaded Pole. Because they are inherently current limiting, Shaded Pole motors can simply be controlled via voltage control, ie a rheostat. So lowering the voltage lowers the torque, which indirectly results in a lower speed. In a PSC motor, the capacitors are always in the circuit, but are in series with the windings so the dI/dt is dampened by the inductance, and because there is no speed switch, the capacitors are DESIGNED to be in the circuit continuously. Therefore the single phase VFDs that you see discussed can ONLY be used on PSC (or Shaded Pole, but that's pointless) motors, they CANNOT be used on CSIR or CSCR induction motors.

Do you have Table fan, ceiling fan or Mixer grinder in your Home?...check how the speed is controlled.