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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
Are wire wound resistors used in parallel circuits?
Can be.
Wire wound resistors might take more power, or offer better precision, or custom resistance values. Wherever, whenever those features are desirable, whether its a series or parallell circuit, a wire wound resistor might be used.
How do you make an impedance- and level-matching transformer?
You'll need to decide *which* one you want.
An impedance-matching transformer has a defined primary-to-secondary turns ratio.
This *may* give the level match that you want, it may not.
Alternately, you can design for a level match, which also *may* give the impedance ratio you want, it may not. It also has a defined turns ratio, but this may not meet an impedance-matching requirement.
For impedance matching find the ratio of impedances, take its square root, and use that as the turns ratio:
2400 ohms to 600 ohms has an impedance ratio of 4:1, so its turns ratio will be (sqrt4) = 2:1.
To level-shift 1.23 volts (+4 dB) to 300 mV (-10 dB), the ratio is (1.23/0.3) approx 4:1.
From the above, you could match 2400 ohms to 600 ohms, but *not* +4 dB to -10 dB with the one transformer.
Why Back EMF occur in only dc motor?
It doesn't. It exists in all electrical machines, d.c. or a.c., motor, generator, or transformer.
What is the purpose of having a low impedance for transmission lines?
Low impedance also improves power transfer capacity of the line..
What size motor does a chainsaw have?
The motor size of most chainsaws are approximately 2 cc. There are, however, different size motors that range from 2 cc to 4 cc.
What is resistance start capacitor run?
most capacitors will measure infinite resistance
starting capacitors are used to set up a rotating magnetic field by phase shifting a coil in a single phase motor
when the motor gets up to speed a centrifugal switch will disconnect the capacitor
this happens at a random time and can leave the capacitor with a charge easily 4x the applied ac voltage (+/-1,000V)
so some capacitors rated as starting capacitors will have an internal bleeding resistor
Gas discharge lamp ballast capacitors sometimes have discharge resistors.
Microwave ovens have capacitors usually in a voltage doubling configuration
(+/-20,000V) most have an internal bleeding resistor.
Never rely on this resistor being intact or even present.
It can have fatal consequences.
the internal resistors are sized to discharge the capacitors in tens of minutes
Tc = R * C ( seconds = ohms * farads )
The question is defective. It talks about plural 'lights', but it doesn't tell how many
there are, or in what configuration they're connected to the 12-volt power supply.
All of that stuff has a substantial effect on the correct answer. (But I don't think
the 10m length of the cable has any at all.)
Where does the voltage that is necessary for field excitation on the rotor originates from?
The excitation current is provided by a small self-excited pilot generator, attached to the same shaft as the alternator's rotor.
What is inter-turn fault in three phase motor?
An 'inter-turn' fault occurs when adjacent turns of the same winding are short circuited (due, for example, to insulation breakdown). This affects the turns ratio of the transformer. An 'inter-winding' fault occurs when there is a short circuit between adjacent windings (coils) due to insulation breakdown, and can lead to a catastrophic failure of the transformer.
How much does a silent diesel generator usually cost to buy?
A silent diesel generator usually costs around $1300.00. The highest price for one can be found at $5809.06, while the lowest can be found for $1378.00.
What is the number of turn in single phase motor?
If you really do mean the number of 'turns', then you cannot really determine this, as it is determined as a part of its design process and can vary considerably from machine to machine.
If, on the other hand, you actually mean 'windings' ('coils') then, typically, there are two: the 'main winding' and the 'auxiliary winding'. The purpose of the auxiliary winding is to supply a magnetic field that is out of phase with the main winding and which then results in a rotating magnetic field necessary to start the motor and turn in in the desired direction.
How much single phase meter can bear load?
Answer for UK, Europe and countries running a 50 Hz supply service.
Common single phase meters for a 240 v system can take a 60 amp or sometimes a 100 amp load for domestic use.
What is frictional kw ac motor?
Why resistance of germanium increases on decreasing temperature from room temperature to 80 Kelvin?
loss of free current carriers as temperature drops.
Does overload relay detect phase reversing of the 3 phase motor?
No, three phase motor overloads just monitor the motor's lines for an overload. Once detected the circuit holding the magnetic starter in will drop out and take the motor off line.
What does the magnetic DC connector do in the Apple power adapter?
The Magnetic DC is not a vital component of the Apple Power Adapter. Rather, it is a guiding mechanism, that helps guide the plug into the jack for a more secure connection.
When resistors are connected in series then what happens to the watt?
Resistors are rated in wattage so the lowest wattage rating will be the wattage of the series circuit. It will be able to handle that power any more and the lowest wattage resistor could be damaged and fail.
Another Answer
When two or more resistors are connected in series, the resistor with the lowest resistance will operate at the highest power. If the power developed by a resistor exceeds its rated power, then the resistor may burn out.
Why are use thin wire in phase of transformer?
I think you mean 'winding', rather than 'phase'? The cross-sectional area of the conductor must be such that it can carry whatever current the winding is designed to carry -if the current is low, then the cross-sectional area (and, hence, its thickness) can be low.
Which laptop is use for PLC programming?
Almost any PC can be used for programming almost any PLC system
The programming interface will be either a serial port, a USB port of increasingly, an Ethernet port.
The PC will usually require the appropriate development software that is supplied, in most cases, byt eh PLC manufacturer.
if this is the one in your car the rotor has slip rings where you can put 12v dc
which will give over 100v with no load
old cars have external regulator 3-4 wires
new ones have one wire all circuits in one little lump of epoxy
the stator is 3 phase
delta or Y - 6 or 3 diodes
the rotor a 12 v DC magnet with slip rings
the diodes sometimes fail
the brushes are only good for about 10 years
usually to trouble shoot just start the car and see if the battery voltage increases.
Is the load of elevator motor depend on building height?
no,elevetor motor depends on size of elevetor & how many persons are accomodate in elevetor.
How do you conduct leak test to a power transformer?
1. Test Method
1) Breather separated from main body, body clean by Air.
2) Nitrogen(Dry air) through the transformer to the body's respiratory system piping at a pressure of 0.35kg/㎠ injection.
3) Pressurized leakage area and then left in place for 12 hours after the inspection.
4) Record the start of the test, the injection pressure and oil temperature(ambient temperature) will vary depending on the oil temperature and the pressure of nitrogen(N2).
5) If the leakage area in case of a fastening portion and gasket area and re-check the pressure(leaks) to restart the test. (In this case, the pressure holding time is restarted.)
How many meters of wire make one ohm?
The resistance (ohms) of a conductor depends on a number of factors including the type of material, its thickness and the temperature.
There are charts that will tell you the resistance of different sizes of wires and the correction factor to use for non-standard temperatures.
What is house load of power plant run parallel with grid and how to calculate it?
House Load of a Power Plant is also known as Auxiliary Power Consumption or Units Used on Works.
It is the electrical power needed to drive the pumps and fans that support the operation of the power plant.
Typically the power plant metering is set up to measure the electricity produced by the generator at the terminals. A seperate meter will measure the electricity used by the auxiliaries, at the unit transformer.
Auxiliary Power Consumption is often expressed as a percentage of Units Generated, so:
Aux Power = ( Units Used on Works / Units Generated ) x 100 %
% MWh MWh
Typical Auxiliary Power Consumption depends on the type of plant:
Plant Type
%
Coal-fired Thermal
6.5 - 8.0
Open Cycle Gas Turbine
2.5 - 3.5
Combined Cycle Gas Turbine
1.0 - 1.5
How can you hook a 230v 3 phase lathe to 480v 3 phase incoming power?
Inspect all motor labels and see if they are dual voltage motors. If they are, they should have a label on them telling you how to convert the motors for 480 volt. This is a relative simple task. Converting to 480 volts will lower the motor current to half of the 230 volt rating, so you will have to change the overload heaters in the individual motor starters. You need to do this to protect the motors in case of overloading. Last the control transformer will need to be reconnected for 480 volt.
