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I have seen this statement in a question paper. I was asked to prove it but I can not find the logic. You are right. The question itself is erroneous. Starting current in star would be 1/3 that in delta and not 1/√3.


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In the time of starting in star-delta starter we first connect the motor winding in star formation. In this case we are delevering only 230V each winding. When voltage is reduced current is also reduced by the ohm's law V=IR,Where R is constant. When motor picks up the speed above the 33% of rated we change the winding connection to the delta by activating ...


0

It will free run, no torque could be produced. However it depends on the installed system. There is a possibility for example to have both: regeneration unit to feed back the excess of energy back to mains, a braking unit with braking resistor and a buck power supply for electronics that is supplied from DC link, optionally also DC link capacitors. In such ...


0

Brush lifting Repulsion Start / Induction Run motors are museum pieces. Very cool to watch them start, especially if you can record it from the brush end and play back in slow motion. But they are not so fun to own, because they were horribly inefficient.


1

I agree that using the \$\omega_m\$ to produce a time-varying observer is a valid and intuitive approach. The "theoretical correctness" of it will mostly depend on two aspects, and both will require some reading and research on your part. (1) the criterias you want to guarantee for the closed-loop system. This mostly concerns stability guarantees ...


0

As Neil_UK has answered, you can't get a "uniform speed" motor. What you can (and must) do is to measure the cable speed and adjust the motor appropriately. This might be as simple as taking a small generator, putting a (rubber) pulley on it, then fixing the generator so that movement of the cable causes the pulley to rotate. Your computer would ...


1

When choosing a motor, thinking about torque first is not the way to go. As you have pointed out in your question, you can vary the torque simply by varying the size of the winding drum. You need to worry first about the power of the motor. This gives you the weight, cost and power supply requirements. Then an appropriate gearing will give you the right ...


6

'3 HP' marked on the motor name plate would be based on the measured full load torque at the rated speed (HP = full load torque kgm * full load speed RPM / 716). The power factor of a single phase induction motor would generally be between 0.5 and 0.8. Assuming a power factor of 0.65 the motor input HP would be 230 x 20 x 0.65 / 735 = 4 and its efficiency 3/...


19

The current marked on a motor should be the continuous, full-load operating current. The power marked on a motor should be the full-load mechanical power delivered by the shaft. A 3 Hp motor should deliver about 2240 watts. 2240/4600 is 0.487. That tells you that the motor's full-load power factor multiplied by its full load efficiency is 0.487. For a rough ...


2

Superconductors are impervious to magnetic fields, so if you have a superconducting rotor no fields lines will enter it. (or pass through the apertures of the squirrel cage) With no field lines in the rotor there will be no torque. you could possibly get it running synchrounosly as a variable reluctance motor. but you'd need a way to start it, and there ...


1

Using the usual equivalent circuit, the electrical power converted to mechanical power is calculated as the power dissipated in R2x(1-s)/s where R2 is the rotor resistance. That would seem to require a finite rotor resistance. The rotor resistance is quite small in most induction motors, but the other impedances in the equivalent circuit are also quite small,...


3

The FOC already does all of this. If the motor's actual velocity is higher than it's velocity setpoint, then you will have a generator mode. You can even control the torque with Iq setpoint. For example: if n>0 // positive direction Iq= -Iq_set; // negative torque (braking) elseif n<0 // negative direction Iq = Iq_set; //positive torque (braking) ...


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A machine is usually designed to utilize the materials as effectively as possible. An induction motor rotor of a given diameter and length can be effectively used to produce a certain torque in a two pole machine. If you have an effective design with a certain number of slots and winding configuration for a given machine, the objective for the design of the ...


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