Why is 50 hz current hazardous

When it does, the starting torque of the motor is suddenly reduced. It could fail to speed up further and never reach normal running speed.

Electrical machines designed for 50Hz can usually work safely in 60Hz power supply, but not applicable to 60Hz machines to be run in 50Hz power supply. Equally, the system can be used when 60Hz equipment is required to operate from a 50Hz power supply. Unless specified by the manufacturer to operate on both 50Hz and 60Hz, appliances may not operate efficiently or even safely if used on anything other than the intended frequency.

The voltage and frequency of alternating current AC electricity used in homes varies from country to country throughout the world. Insulation on wires leading to an appliance has worn through, allowing the two wires to come into contact. Such an undesired contact with a high voltage is called a short. For example, if V is V and r is 0. Thermal energy delivered at this rate will very quickly raise the temperature of surrounding materials, melting or perhaps igniting them.

Figure 1. A short circuit is an undesired low-resistance path across a voltage source. One particularly insidious aspect of a short circuit is that its resistance may actually be decreased due to the increase in temperature. This can happen if the short creates ionization. These charged atoms and molecules are free to move and, thus, lower the resistance r.

High voltages, such as the V AC used in some industrial applications, lend themselves to this hazard, because higher voltages create higher initial power production in a short.

Another serious, but less dramatic, thermal hazard occurs when wires supplying power to a user are overloaded with too great a current. If either I or R w is too large, the wires overheat. If Similarly, if a wire with a 0. Fuses and circuit breakers are used to limit excessive currents. See Figure 1 and Figure 2. Each device opens the circuit automatically when a sustained current exceeds safe limits.

The one shown here has a bimetallic strip that bends to the right and into the notch if overheated. The spring then forces the metal strip downward, breaking the electrical connection at the points. Figure 2. Schematic of a circuit with a fuse or circuit breaker in it. Fuses and circuit breakers act like automatic switches that open when sustained current exceeds desired limits. Fuses and circuit breakers for typical household voltages and currents are relatively simple to produce, but those for large voltages and currents experience special problems.

For example, when a circuit breaker tries to interrupt the flow of high-voltage electricity, a spark can jump across its points that ionizes the air in the gap and allows the current to continue flowing. Large circuit breakers found in power-distribution systems employ insulating gas and even use jets of gas to blow out such sparks. Here AC is safer than DC, since AC current goes through zero times per second, giving a quick opportunity to extinguish these arcs. Electrical currents through people produce tremendously varied effects.

An electrical current can be used to block back pain. The possibility of using electrical current to stimulate muscle action in paralyzed limbs, perhaps allowing paraplegics to walk, is under study. TV dramatizations in which electrical shocks are used to bring a heart attack victim out of ventricular fibrillation a massively irregular, often fatal, beating of the heart are more than common.

Yet most electrical shock fatalities occur because a current put the heart into fibrillation. A pacemaker uses electrical shocks to stimulate the heart to beat properly. Some fatal shocks do not produce burns, but warts can be safely burned off with electric current though freezing using liquid nitrogen is now more common. Of course, there are consistent explanations for these disparate effects. The major factors upon which the effects of electrical shock depend are.

Table 1 gives the effects of electrical shocks as a function of current for a typical accidental shock. The effects are for a shock that passes through the trunk of the body, has a duration of 1 s, and is caused by Hz power. Figure 3. An electric current can cause muscular contractions with varying effects.

Those that close the fingers are stronger than those that open them. Our bodies are relatively good conductors due to the water in our bodies. Given that larger currents will flow through sections with lower resistance to be further discussed in the next chapter , electric currents preferentially flow through paths in the human body that have a minimum resistance in a direct path to earth. The earth is a natural electron sink.

Wearing insulating shoes, a requirement in many professions, prohibits a pathway for electrons by providing a large resistance in that path. Whenever working with high-power tools drills , or in risky situations, ensure that you do not provide a pathway for current flow especially through the heart. Very small currents pass harmlessly and unfelt through the body. This happens to you regularly without your knowledge.

The threshold of sensation is only 1 mA and, although unpleasant, shocks are apparently harmless for currents less than 5 mA. The potential difference between two terminals is Volts and the frequency of the incoming supply is 60 Hz reaches 60 cycles per second.

Note: Both the power system has advantages and disadvantages, but 50 Hz power system have some extra advantage over 60 Hz power system. Here the eddy current loses is directly proportional to the square of generation frequency and hysteresis loss is directly proportional to the frequency, Hence, the reducing frequency of the generation reduces the total constant loses of the machine.

In this, by reducing the frequency of the alternating current, we can reduce the impedance loss of the circuit. Let see how? As we know Impedance Z is the vector sum of resistor R and inductive reactance Xl of the circuit. From the equation Xl you can see the reducing frequency of the circuit, the inductive reactance of the circuit get reduces. Hence the Total impedance of the circuit also reduces. Increase Voltage V, decrease the current flow of electron or charges flowing through the circuit.

If your circuit carries the larger quantity of current, you should increase the size of the conductor. If you supply a high voltage, the total current reduces and you do not want to go for larger size conductor. Copper and aluminum are mainly used in the electrical system to carry current to the other circuit. Example: Take a steam power plant which is running with coal and the coal to the steam ratio of the boiler is 4. But the Steam to power ratio is 2.