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To understand how voltage standards for motors are set it is important to know the basics of the power systems they operate on. In general, utilities that supply power in the USA, and most other 60 cycle countries, are required to provide power to the incoming point of a facility in multiples of 120 volts. Thus incoming equipment, such as circuit breaker panels, are rated in multiples of 120 volts. The common voltages are 120, 240, 480, and 600.
In addition, utilities are obligated by the regional governing authorities, (usually called Public Utility Commissions) to regulate the voltage within a fairly narrow range such as plus or minus 5%.
For example, in most single phase residential systems the voltage is 120/240. It is brought to the building with 3 wires, one being a neutral and the other two having voltages 120 volts different from the neutral wire. The voltage difference between the two "hot" wires is 240 volts.
In 3 phase systems the situation is a bit different. There are 3 phase, 3 wire, ungrounded systems where the voltage between the three wires is 240 volts. The big brother of that system is the ungrounded 3 phase, 3 wire 480 volt system. Ungrounded systems are usually found in older facilities.
In newer installations, the two most popular systems are called 4 wire grounded wye systems. The low voltage version is represented by a 120/208 volt system. The higher voltage version it is a 277/480 volt system. On both of these "grounded wye" systems, the low voltage portion (120 or 277 volts) is only available as single phase. The high voltage (208 or 480 volts) is available as either single phase or 3 phase. It should be noted that in the 4 wire grounded wye systems the high voltage is 1.73 times (the square root of 3) higher than the low voltage. These grounded wye systems are generally felt to be safer and more flexible than the older ungrounded systems. The flexibility comes from the ability to handle single phase lighting circuits, that operate at 120 volts or 277 volts, from the same system that feeds the 3 phase circuits for motors, equipment for heating, air conditioning, elevators, and industrial machinery.
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Why high voltage is kept open in open circuit and low voltage is shorted in short circuit test?
In Short circuit test High Voltage side is feeded with 2-5% of the High Voltage rating to circulate approximately full load current in low voltage winding by short circuiting it. Low voltage is generally short circuited to facilitate measurements because it is more difficult to measure the quantities at high voltages.
How does the low-voltage circuit controls the power to the high-voltage circuit?
Through a relay or some other kind of high voltage switching device.
How do i switch a 3 phase motor from low to high voltage?
You can't. You must supply the motor with it's required voltage. If it's a dual voltage motor, follow the wiring schematic on the motor nameplate to switch from low to high voltage.
What is high voltage motors and low voltage motors?
None: "high tension" is just another way of saying "high voltage".
Which one of the following statements is true of a split phase motor when it is starting the speed is high the torque is high the current is low the voltage is low?
The first statement is true, the motor needs a power source to operate.
What causes high and low currents?
In electricity? High voltage ,high currents. Low voltage, low currents.
Electrical Properties of Transformers why you use it?
Transformers are used to convert electricity from high voltage to low voltage and from low voltage to high voltage.
How you understand which side of a transformer is high voltage side and low voltage side?
at high voltage side, current is low. hence the size of conductors is reduced or small. At low voltage side, current is high. Hence the size of conductors is large.
What does a coil on a gas lawnmower do?
it converts a low voltage to a high voltage.
How can you categorize projects into high or low voltage projects?
You can categorize the projects into either low or high voltage projects based on the power consumption.
Is it possible to have high voltage with low current?
yes
What is the low voltage and high voltage availability for heavy engineering workshops?
0.1 and 0.2
Can connect high voltage supply to low voltage device?
Yes, but it won't be pretty.
Why does a low voltage circuit create more amperage than a high voltage circuit?
That depends on what you mean. If you mean why does a circuit which has a high voltage side and a low voltage side have a greater average current on the low voltage side, it is probably because of power conservation: P = IV. If this is not what you mean, you will have to be more specific!
What are the difference between high voltage and low voltage?
Hi, The main difference is Fuel consumption. High current genertors always consumes much fuel because the load on the engine will be high. The high voltage low current generators doesn't need much fuel to run. You can understand this by comparing 1 kva and 5 kva single phase generators. For both generators voltage will be same (230v) But output current differs. So the fuel consumption also differs. But you get a high current source. Low voltage high current generators can be used for welding kind of stuffs which needs high current to do the job. If you have step down transformer then you can save the fuel.
Why high voltage is kept open in open circuit and low voltage is shorted in short circuit test?
In Short circuit test High Voltage side is feeded with 2-5% of the High Voltage rating to circulate approximately full load current in low voltage winding by short circuiting it. Low voltage is generally short circuited to facilitate measurements because it is more difficult to measure the quantities at high voltages.
How does the low-voltage circuit controls the power to the high-voltage circuit?
Through a relay or some other kind of high voltage switching device.
