Electrical Engineering

There is no such thing as a multi phase transformer. A transformer has one phase input and one phase output. There may be multiple windings on input and on output, but they are all in phase, insofar as the power factor allows it.

What we call a three phase transformer is really three transformers operating together, one on each of the three phases. They do not share the phases. They do not share windings. They do not share cores. They do not share magnetic fields. They are independent. They only thing they might share is they same physical container.

Star-delta configuration for three transformers (emphasis on plural) is a common configuration, although star-star is supposed to be better from an eddy current perspective. It comes down to the objectives of the load, and whether or not there there is a neutral involved, and where the neutral is connected. You can still have a neutral in star-delta, but it won't be centered in the middle of the three phase power - it will be centered in the middle of one of the split phase single phases, in the style of 120/240 split phase like typical residential power. Again, it comes down to objectives.

Three-phase ('polyphase') transformers are widely-used in electricity transmission and distribution systems.

A three-phase transformer typically comprises a common, three-limb, silicon-steel core, around which are placed three pairs of primary- and secondary-windings, entirely enclosed within a sheet-steel tank containing a mineral oil for the purpose of insulation and cooling. For a delta/wye configuration, the primary winding is accessed through three ceramic bushings, while the secondary winding is accessed through four ceramic bushings.

Three, separate but identical, single-phase transformers can also be connected together to create a 'three-phase transformer bank'. Three-phase distribution transformer banks are more common in North America than in the UK, where three-phase transformers are the norm.

Most power transformers (i.e. transformers used in the transmission system) are three-phase transformers, although at really high MV.A levels, three-phase transformer banks are used because their very large physical size makes them easier to transport and install.

In the UK, distribution transformers normally use the delta/wye configuration, because the high-voltage primary is supplied from an 11-kV three-phase, three-wire, system, while the low-voltage secondary supplies a three-phase, four-wire, system with a line voltage of 400 V and a phase voltage of 230 V.

In North America, a three-phase distribution transformer's secondary configuration is normally delta-connected, with one phase centre-tapped in order to supply the standard, split-phase, 240/120 V low-voltage system.

If, by 'storage element', you are are referring to the inductive and capacitive components (?), then the answer is yes. The voltage drop across these components is given by:

• VL = I XL
• VC = I XC

In fact, at resonance, if the resistance is low, then VLand VC can be very much higher than the supply voltage.

An electric motor uses electrical energy to produce mechanical energy. The reverse process, that of using mechanical energy to produce electrical energy, is accomplished by a generator or dynamo. Traction motors used on locomotives and some electric and hybrid automobiles often perform both tasks if the vehicle is equipped with dynamic brakes. Electric motors are found in household appliances such as fans, refrigerators, washing machines, pool pumps, floor vacuums, and fan-forced ovens. They are also found in many other devices such as computer equipment, in its disk drives, printers, and fans; and in some sound and video playing and recording equipment as DVD/CD players and recorders, tape players and recorders, and record players. Electric motors are also found in several kinds of toys such as some kinds of vehicles and robotic toys.

An electric motor converts electrical energy into mechanical energy. Most electric motors operate through interacting magnetic field and current carrying conductors to generate force but a few use electrostatic forces.

There is no equation for Ohm's Law. Ohm's Law simply tells us that, for ohmic or linear materials, the ratio of voltage to current is a constant.

The equation you are, presumably, looking for is derived from the definition of the ohm, not from Ohm's Law, and that is resistance is voltage divided by current.

Generally, yes - a 35 uF capacitor is close in value to a 30 uF capacitor - but it depends on the circuit requirements. If you are talking about a tuned filter, I would say no. If you are talking about a power supply filter, I would say yes. Just keep in mind that it takes more current to charge a larger capacitor, so you need to consider the current rating on the diode(s). Of course, if this mattered in a power supply, then I would also say that the design margins are too tight. Again, 35 versus 30 is not a big difference - again, sometimes. Also, you need to ensure that the voltage rating of the new capacitor is equal to or greater than the voltage rating of the old capacitor.

I've received a message that this capacitor is a motor starting capacitor in an air conditioner. My answer is this...

Then I would consider it a tuned circuit, because phase angle of the power in the start windings would matter to the proper starting of the motor. However, my root analysis holds - you need to consider the system's design requirements.

If any motor engineers out there are willing to take a stab at this, please do. I have flagged the question to attempt to get a better answer.

Nothing noticeable. DC power is not transmitted between the coils of a transformer. There would be no current on the other side of the transformer, unless the power of the source was constantly modulated. bescause flux does not change its state.

after some time excessive heat is produced and winding may burn

A transformer's primary winding presents two forms of opposition to current flow. The first is resistance, which is dependent upon the length, cross-sectional area, and resistivity of the wound conductor. The second is reactance, which depends upon the inductance of the winding and the frequency of the supply. Resistance opposes both AC and DC currents, while reactance opposes only AC current. In the case of a transformer's windings, the resistance is relatively low while the reactance is very high. When an AC voltage is applied, the reactance is sufficiently high to limit the value of AC current flowing through the winding. However, the resistance is so low that a large current would flow if an equivalent DC voltage was applied instead. This current would likely overheat the winding's insulation, resulting in its breakdown, causing a short circuit(s) which could severely damage the transformer.

The advantage of a full wave rectifier is that it produces less ripple and the ripple has a higher frequency, making it easier to filter.

The advantage of a half wave rectifier is it is simpler and less expensive as it needs fewer components.

Which is best in a given application however requires making other tradeoffs that are out of scope for this question as they cannot be determined without knowing the details of the specific application. So neither is universally the best.