LIGHTING/SURGE PROTECTOR CIRCUIT

The basic surge suppression circuit
shown below consists of a VDR** (Voltage Dependent Resistor) and gas surge
suppressor (GDT) connected in series. The protection circuit is connected
between live and mains lead. Normally no current flows through GDT and VDR1.
When the voltage between the terminals is higher than the sum of
voltage ratings of GDT and VDR1 (here both GDT UZ470B and VDR S20K250
has 250v 16A rating), current starts to flow through those components. If more
the voltage raises then more current starts to flow through GDT and VDR1.When
the current is normal, the circuit is reset and resumes it’s functioning. Thus
the current cannot be raised much over that predetermined value. When the
voltage again goes back to normal values G1 and VDR1, the conducting stops and
the circuit remains normal. If the flowing current is more than the
specified value of main self-resettable fuse, the fuse will break and the
circuit will be protected. After the current is normal, the fuse resets and
continues its functioning (protection against short circuit and overload). The
circuit is designed to protect sensitive electronic devices against overvoltage
transients in normal mains voltage and overload/ short circuit. Two neon pilot
lamps are also provided with the circuit diagram to show the status of input
and load suppl
Advantages
1) Normal working
voltage = 230v AC/DC
2) Maximum current
rating=16A
3) Cut-off current
=16A
4) Cut-off voltage=
>300v R.M.S
5) Protection against
overloads
6) Protection for
short circuit
Applications
1) Protection for
sensitive components
2) Protection for
motor devices
3) Telephone line
protection
4) SMPS protection
**A VDR (Voltage Dependent Resistor) is an electronic component with a “diode-like” nonlinear current–voltage characteristic. The name is a portmanteau of variable resistor. VDRs are often used to protect circuits against excessive transient voltages by incorporating them into the circuit in such a way that, when triggered, they will shunt the current created by the high voltage away from the sensitive components. A VDR is also known as Voltage Dependent Resistor or VDR. A VDR’s function is to conduct significantly increased current when voltage is excessive.)
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