Power voltage and current relationship for an induction motor connected to , say, a centrifugal pump?

Question

It is said that when a induction motor is started direct on line, it'll generate a high torque, which will lead to it accelerating in uncontrolably. what is meant by " GENERATE A HIGH TORQUE" ? bcoz torque is force * shaft radius and radius is fixed, this means high tangential force on the motor shaft, how does this increase within the motor as the load on the motor increases?

It is also said that, then the network has to supply a large inrush current, a very high initial level to establish flux in the motor. where does this sudden supply of current i.e. electrons come from?

I have this doubt bcoz, the supply voltage is fixed, say through the socket in the wall or is it?. why and where does this sudden surge of current come from. If u find this question silly

please suggest some websites which can clarify my silly doubts.

thank you in advance.

Answer 1

actually an induction motor or shaded pole motor has very poor torque on startup and it will be very inefficient untill it reaches its rated rpm,a dc or stationary field motor is max torque at any rpm    ,Steve 3 phase power is not household AC generally single phase and single phase Induction motors don't get 50% torque because there is no strong 120 deg phase to chase

Answer 2

When a three-phase induction motor is energized direct-on-line, the power source (i.e. the grid) first supplies a very large (approx. 600% of nominal) current to set up the magnetic fields in the motor.  Subsequently, the energized magnetic fields produce a torque that attempts to rotate the rotor and whatever is connected to it.

The result is a non-zero torque at the instant that the motor is still standing still.  (In fact, this is a common test, in which the motor shaft is briefly blocked from rotating on a test setup and the output torque is measured.)

Depending on the motor particulars, starting torque would most often be in the range of 50 - 200 % of the rated torque full-power, full-speed torque of the motor.

There are some more fundamental electrical concepts, such as where the electrons come from, that you should s[end some quality time reading about.  A simple trip to the local library for a book on physical science, covering electricity and magnetism, should be a good start.

Answer 3

You have some basic misconceptions about electricity. And you need to do some reading. I suggest wikipedia. Look up electricity on that site.

The wall socket supplies a fixed voltage (120 volts in the U.S.) and an amount of current determined by the load. With no load, nothing plugged into the socket, there is zero current. With a light bulb plugged in, there is perhaps 1 amp of current. With a large AC plugged in, there is perhaps 10 amps of current. Much more than that and the circuit breaker will trip to prevent damage.