What is knee voltage?

Knee voltage is the forward voltage at which the flow of the current through the PN junction of the diode increases rapidly. The knee voltage is generally observed in Zener Diodes.

Why is it called knee voltage?

Once the light-emitting diode is connected to an external voltage in the forward bias, the potential barrier height across the PN junction will be decreased. This exact voltage is known as the knee voltage of the LED.

What is the knee voltage and breakdown voltage?

The forward voltage at which the current through the junction starts increasing rapidly, is called the knee voltage or cut-in voltage. The reverse voltage at which P-N junction of a diode breaks down with sudden rise in reverse current is known as break down voltage.

What is the knee point voltage?

The knee point is defined as the voltage at which a 10% increase in applied voltage increases the magnetizing current by 50%. For voltages greater than the knee point, the magnetizing current increases considerably even for small increments in voltage across the secondary terminals.

What is knee voltage formula?

Vkp = 2*30000/120*0.5 =250 Volt

If the knee point voltage calculated on the basis of the power network is higher than the specified knee point voltage of CT, then there is a chance of CT saturation during a fault in the power network, and probably the protection relay will not operate.

? Voltage-Current characteristics of p-n Junction Diode | Knee voltage

Why is knee voltage important?

Knee point voltage is nothing but a magnitude of the saturation limit of the current transformer. Each protection class CT has to be operated in its Non saturation region. So that we have to calculate the maximum allowable voltage limit, that can be applied to the secondary winding of the current transformer.

What is knee voltage of CT?

According IEC, Knee Point Voltage of a Current Transformer is defined as the voltage at which 10 % increase in voltage of CT secondary results in 50 % increase in secondary current. If you carefully read the definition, you will notice that it is something related to saturation of Current Transformer CT.

What is CT ratio?

The CT ratio is the ratio of primary current input to secondary current output at full load. For example, a CT with a ratio of 300:5 is rated for 300 primary amps at full load and will produce 5 amps of secondary current when 300 amps flow through the primary.

What is the PT ratio?

The prothrombin time ratio is the ratio of a subject's measured prothrombin time (in seconds) to the normal laboratory reference PT. The PT ratio varies depending on the specific reagents used, and has been replaced by the INR.

What is knee point and ankle point?

Hence one typical curve can be drawn from this relation between secondary voltage and excitation current as shown below. It is clear from the curve that, linear relation between V and I_e is maintained from point A and K. The point ′A′ is known as ′ankle point′ and point ′K′ is known as ′Knee Point′.

What is meant by breakdown voltage?

Definition of breakdown voltage

: the potential difference in volts that when applied across a layer of electrically insulating substance is just sufficient to initiate a disruptive discharge.

Is knee voltage same as barrier potential?

Detailed Solution. The forward voltage at which the current through PN junction starts increasing rapidly is known as knee voltage. The Knee voltage of a crystal diode is approximately equal to barrier potential.

What is knee current?

Zener Knee Current: The reverse current that flows through the zener diode while at the break-down voltage. Zener current shown as Iz in the data sheet. Zener Voltage: The break-down voltage of a zener diode.

What is knee voltage in photoelectric effect?

There is a "knee" in the curve where the current begins to increase rapidly. The applied voltage at the "knee" is proportional to the minimum emission voltage for light. From the discussion in Part III the voltage at the "knee" must be approximately V_D. Since we need V_D to apply Eq.

Whats a rectifier do?

A rectifier is a device that converts an oscillating two-directional alternating current (AC) into a single-directional direct current (DC). Rectifiers can take a wide variety of physical forms, from vacuum tube diodes and crystal radio receivers to modern silicon-based designs.

What is a normal INR?

In healthy people an INR of 1.1 or below is considered normal. An INR range of 2.0 to 3.0 is generally an effective therapeutic range for people taking warfarin for disorders such as atrial fibrillation or a blood clot in the leg or lung.

What is need of CT and PT?

The current transformer and potential transformer (also called voltage transformer) are both measuring devices. A CT lowers the current signals for measurement purposes, while a PT lowers high voltage values into lower ones. The transformers are designed to measure whether power systems are both accurate and safe.

What causes PT INR to be high?

You may have high PT/IR results if: You haven't been taking the proper dose of warfarin. You've taken over-the-counter medicines, such cold medicines, or vitamin supplements, that can interact with warfarin.

How do you calculate CT size?

What is class1 CT?

The class designation is an approximate measure of the CT's accuracy. The ratio (primary to secondary current) error of a Class 1 CT is 1% at rated current; the ratio error of a Class 0.5 CT is 0.5% or less. Errors in phase are also important, especially in power measuring circuits.

What is S1 and S2 in CT?

Terminals S1/S2 (k/l)

The connections of the primary winding are designated "K" and "L" or "P1" and "P2", and the connections of the secondary winding are designated "k" and "l" or "S1" and "S2". The polarity must be established such that the "flow direction of the energy" runs from K to L.

What is RCT in CT?

A CT equivalent circuit. Lm is the saturable magnetisation inductance, L is secondary of an ideal current transformer, RCT is resistance of the CT secondary winding, RW is resistance of wiring and RL is the burden i.e. the protection relay.

What is 5p in current transformer?

The Number '5' indicates the accuracy of the CT. When the current flows through the 5P20 protection class CT is 20 times of the rated primary current, the CT reads within the composite error of 5 %. If the current is above 20 times then the CT will saturate.

What is accuracy limit factor of CT?

The accuracy limit factor (ALF) of the CT is defined as the ratio of rated accuracy limit primary current to rated primary current. The protection class CT is marked as 5P10 or 5P20.

What is knee voltage in Planck's constant?

Voltage range – 1 to 2 volts.