What is surge current rating of thyristor?

Surge current rating specifies the maximum non-repetitive or surge current that the SCR can withstand for a limited number of times during its life span. The manufacturers specify the surge rating to accommodate the abnormal conditions of SCR due to short circuits and faults.

What do you mean by surge current?

[′sərj ‚kə·rənt] (electricity) A short-duration, high-amperage electric current wave that may sweep through an electrical network, as a power transmission network, when some portion of it is strongly influenced by the electrical activity of a thunderstorm.

What do you mean by dv dt rating of thyristor?

dv/dt: dv/dt rating of thyristor indicates maximum rate of rise of anode voltage that will not trigger the device without any gate signal. The device is assumed to be operating under rated blocking voltage, forward current and junction temperature before the surge current occurs.

What is thyristor current?

Thyristor are current operated devices, a small Gate current controls a larger Anode current. Conducts current only when forward biased and triggering current applied to the Gate. The thyristor acts like a rectifying diode once it is triggered “ON”.

What is peak working reverse voltage of a thyristor?

For rectifier applications, peak inverse voltage (PIV) or peak reverse voltage (PRV) is the maximum value of reverse voltage which occurs at the peak of the input cycle when the diode is reverse-biased. The portion of the sinusoidal waveform which repeats or duplicates itself is known as the cycle.

How is surge current measured?

To measure the inrush current, technicians can use either a hard-jawed clamp meter or a flexible current probe. Only meters that offer an inrush button can measure inrush current.

How is surge current calculated?

Inrush current calculations: Approximately inrush current I(peak) is equal to the ratio between the root 2 times of maximum applied voltage to DC winding resistance. This calculation gives you the approximate value of the inrush current to understand.

How do dV dt and di dt rating effect SCR?

As the time increases, voltage across the capacitor builds up at slow rate such that dv/dt across the capacitor is too small to turn ON the SCR. If the SCR is turned ON, the capacitor starts discharging which causes a high current to flow through the SCR. This produces a high di/dt that leads to damage the SCR.

What is the function of the thyristors?

Thyristors are mainly used where high currents and voltages are involved, and are often used to control alternating currents, where the change of polarity of the current causes the device to switch off automatically, referred to as “zero cross” operation.

What does a thyristor do in a circuit?

The primary function of a thyristor is to control electric power and current by acting as a switch. For such a small and lightweight component, it offers adequate protection to circuits with large voltages and currents (up to 6000 V, 4500 A).

What is the difference between latching current and holding current of a thyristor?

The main difference between latching and holding current of SCR is that latching current is related with turn on process while holding current is related with turn off process of SCR. But once anode current becomes more than latching current, gate losses its control and it may be removed.