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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
What is a form z relay contact?
A form Z relay contact is one of six common types of contact configurations. A type Z is a single pole, double throw, double break configuration. There is no common hot terminal. It is usually used where two separate circuits need to be opened at the same time.
HT drives are the pumps or motors operate at more power typically more than 0.5 Amps at 110 or 220 V DC whereas LT drives operate at lesser power less than 0.5 Amps at 24 V DC or 240 V AC.
What is the FLA at 230 volts with nameplate amps of 20 and voltage of 230?
If the nameplate states 20 amps then that is the full load amperage when the motor is running. The start up current on the motor could reach 300% of the FLA depending on the type of motor and the load that is connected to the motor.
Fuse size for 7.5 HP 3 Phase 440 Volt Motor?
The electrical code states that a 7.5 HP 460 volt three phase motor draws 11 amps. For fuse sizes, non time delay - 30 amps, time delay type D - 20 amps and if using a breaker it will be 30 amps. Minimum wire size is #12 and the maximum setting of overload devices will be 13.75 amps
It will take slightly less than one second (0.92 seconds) to charge a 1000uF capacitor to 12 volts through a 1000 ohm resistor if your power source is 20 volts.
The time constant of a 1000uF capacitor in series with a 1000 Ohm resistor is 1 second. (1x10-3 Farads times 1x10+3 Ohms = 1 second) It takes 1 time constant to reach 63% of a step change, 2 time constants to reach 86% of step change, and so forth using the equation VT = V0 (1 - e (-T/RC)). See notes below
12 is 60% of 20, so it will take about 0.92 seconds for the capacitor to reach 12 volts. In two seconds the capacitor will reach about 17 volts. In five seconds, five time constants, the capacitor will be considered to be fully charged, 99.3%, to 20 volts.
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Notes:
VT is voltage after a given number of seconds. V0 is the total initial voltage, in this case, 20 volts. -T/RC is the negative number of time constants for the exponential equation e-TC, which a charging capacitor exhibits. (More specifically, e-TC is the proportion of voltage across the resistor, while 1 - e-TC is the proportion of voltage across the capacitor.)
This equation is based on the fundamental equation of a capacitor...
dv/dt = i/c
... which states that the slope of the voltage is proportional to current and inversely proportional to capacitance. Plug this into an initial state differential equation, for the case of charging an initially discharged capacitor through a resistor, and you get
VT = V0 (1 - e (-T/RC))
(Derivation requires calculus, and that seems a little bit out of scope for this question.)
Why does current decrease when resistance increases?
Because that's the definition of Ohm's law. Current = voltage / resistance.
Here's one way to think about it. Resistance is the degree of difficulty in moving charge from one place to another. If you increase that resistance, it is harder to move the charge. Current is rate of flow of that charge, hence current goes down.
What are the problems associated with the y-y three-phase transformer connection?
Your third leg is called the high leg and can exceed 180 or more volts. In a 3 phase panel you will loose a third of your circuits unless they are used for motors or other equipment that uses three phase evenly through its function {meaning it doesn't use one leg exclusively for controls or 110V functions. It get a bit involved explaining the windings of a transformer and center taps but suffice it to say one leg gets more than it's share of windings in the transformer. It was used in the early years of industry when single phase 240V systems were the only game in town and they wanted to get more power from the Wye set up prior to delta. It never was popular but a necessity for industry and grew only because of slow development incorporating the 208V delta 3 phase system.
How does interlock mechanism work on a multi rail gear selector?
It is a safety device that prevents selecting two gears at the same time. If that happened the gearbox would be destroyed.
Convert everything to the same unit, for example, to Ohm. Then use the formula for parallel resistances:
1/R = 1/R1 + 1/R2 + 1/R3...
For the case of two resistors, you can also calculate the resulting resistance as product-over-sum:
R = (R1 * R1) / (R1 + R2)
Can you use a 100 mfd in place of a 60 mfd capacitor?
Capacitor values in certain applications can be very forgiving and in others quite critical. In power filtering for example you might be able to get away with the higher value. As long as the larger capacitor has the same or higher voltage rating you can give it a shot provided you understand that by doing so either it won't work or make harm your device.
What are the possible cause that motor compressor trip?
there is a possibility that parts of motor windings has partial damage.
Answerer: The load arm is a balanced mechanical arm use mainly at jetties to load and discharge petroluem or chemicals to a tank onshore. It is used at truck loading bay as well.
Editor: The load arm is a balanced mechanical arm use mainly at jetties to load and discharge petroluem or chemicals to a tank onshore. It is used at truck loading bay as well. Also the load arm is the part of a lever where the load is applied, which is the opposite of effort arm which is where the effort or work is applied.
I assume that you are enquiring about a 'micrometer', the precision measuring instrument, as opposed to a 'micrometre' (to use the British spelling), which is an SI unit for distance? I guess this sums up the problem with the US spelling!
A micrometer has no particular disadvantages -it does exactly what it is designed to do. I suppose you could say that you have to be taught how to read a micrometer is a 'disadvantage', but this is true for most analogue instruments. However, there are digital micrometers which overcome this difficulty.
Can a 460V 3 phase 60Hz electrical motor run safely on a 380V 3 phase 50Hz supply?
its answer is YES because 220 is a phase voltage in three phase system and line voltage for three phase system is 220*1.732=381 or 380. thus motor runs.
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The above answer is wrong. Just because one leg to ground voltage is 220 volts on a 380 volt system does not allow the three phase motor to run off of one leg of a three phase system. A three phase motor is wound with three sets of coils which, if connected as above, the other two motor coils would not get energised.
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When a motor runs on 380V three phase, it is connected in star, which means that one end of each of the three motor windings are connected together to create a star point. The other end of each motor winding is connected to one of the three phases.
If you only have 220V supply, you can still run the motor, but then you need to use a current inverter (or drive) to divide the 220V supply into three phases and the motor MUST then be connected in DELTA. This is achieved by connecting the windings end to end.
Here is a diagram of a delta and a star (or Y) connection
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Diodes are usually rated in amperage. A diode may be capable of handling only a 10th of an ampere. Some diodes called Power diodes may be capable of handling up to 100 amperes per diode. To select the proper diode, you must know what the maximum amperage your circuit is capable of. Then you would select one that would handle at least 120 percent of the amperage your circuit would handle.
What are the best home capacitor banks?
Capacitor banks are more for industrial use than for homes. Industry uses their inductive based (motor) loads more or less continuously where motor loads in the home are more intermittent.
For homes, individual power factor correction is applied to the individual appliances that present an inductive load. These devices are active in that they sense PF, and correct it to 1. I suppose you could do it on a whole house basis, but this would have to be an active PFC to account for the variability of the load as appliances are turned on and off. Biggest offenders in a house are AC units, washers, dryers, spas, etc. Would have to do cost/benefit analysis to see what cost is justified for the smaller motors. Since there are few large offender, it seems that plug in PFCs at each point would be more cost effective to install and operate than a whole house solution.
AnswerCapacitor banks, for the purpose of power-factor correction, have absolutely no relevance whatsoever to residences and, certainly, improving the power factor of a residential load will not reduce your electricity bill. The purpose of power-factor correction, which is only relevant to industrial loads, is to reduce the supply current in order to reduce the amount of copper used in the supply system; it has no effect on the energy used, although companies are penalised for having unnecessarily-low power factors. Your energy meter monitors your residence's supply voltage and the in-phase component of the load current, so measures the energy you consume -regardless of your load's power factor. Any company attempting to sell you capacitors in order 'to reduce your energy bill' are simply attempting to rip you off -end of story!
MSISDN is a number uniquely identifying a subscription in a GSM or UMTS mobile network. Simply put, it is the telephone number to the SIM card in a mobile/cellular phone. The abbreviation has several interpretations, most common one being "Mobile Subscriber Integrated Services Digital Network Number".[1] The MSISDN together with IMSI are two important numbers used to identify a mobile phone. IMSI is often used as a key in the HLR ("subscriber database") and MSISDN is the number normally dialed to connect a call to the mobile phone. The MSISDN follows the numbering plan defined in the ITU-T recommendation E.164. More Details in http://en.wikipedia.org/wiki/MSISDN
What is a BTD when dealing with large HP electric AC motors?
BTD stands for bearing temperature detector.
Why DC rating of Relay contacts is lesser than AC rating you need theoretical approach?
100 v DC is not the same as 100v AC the AC will be 141v which can arc over the contact if rated as 100 v DC.
The deal is that when switches open and close they arc for a short period of time. This is the main factor in wearing out the switch. Because AC automatically alternates back and forth, the arc is naturally extinguished faster. The DC, however, sustains the arc until the switch gap is large enough to shut it down. Therefore, the DC ratings must be lower to provide the same switch life and reliability.
