What modification in the design can reduce the starting current of an induction motor. Or what factors mainly determines the starting current.

 

Depending of your application, if you start a pump you can just close the valve a the pump outlet for 10 secondes when you start the motor and this reduice the motor load.

 

Hi

Buy a softstarter, or a frequency converter, both will solve your problem...

regards tommi

 

The design should establish the start and running conditions.
Essentially this follows for for all types of pump, fan and conveyance systems.
The conveyor application would take into account the empty belt and weights of all gear associated. Drum weights, belt weight, inclination, belt tensioning, friction factor and the like.
Start-up on the empty belt, feed to the belt is introduced proportionately to avoid an overload.

Pumps vary in that a positive displacement and a centrifugal are agreed different applications and gear.
Centrifugal start-up in closed discharge or a calculated recirc mode of low load, ultimately sequencing into the run mode.

It is very important to know the limitations of the equipment.
Many times the manufacturer's technical group can lend insight to your application.
Centrifugals normally are not run with a closed discharge for great length of time.

Hope this helps.
Good Luck!

Best Regards,
Paul

 

Starting current is determined by the motor's "locked-rotor" parameters. Typically, a value is supplied by the manufacturer that relates the starting current in multiples of full-load current. That factor is called the starting-kVA per rated-Hp multiplier.

The effects upon the power system can be reduced by using a reduced-voltage starter. The starter can be either of conventional electro-mechanical design such as wye-delta, part-winding, primary resistor or reactor, auto-transformer, wound-rotor, or an power-semiconductor-based "soft-starter."

Note, either methodology will reduce the nominal starting and available run-up torque by the square of the ratio Vs/Vn, where:

Vs - the motor terminal voltage resulting from the methods above.

Vn - the design voltage of the motor.

An example:

If he starting voltage is reduced to 80% of nominal, then the torque values will be reduced to 64% of expected. These values will impact on the motor's ability to start and then accelerate the driven-machine.

Regards,

Phil Corso,
PE Boca Raton, FL
[[email protected]] ([email protected]) {[email protected]}