A snubber is a device used to suppress some phenomenon, such as:
A snubber is a device used to suppress some phenomenon, such as:

Voltage transients in electrical systems. Pressure transients in fluid systems.
Voltage transients in electrical systems. Pressure transients in fluid systems.

Excess force or rapid movement in mechanical systems.
Excess force or rapid movement in mechanical systems.

Electrical systems
Electrical systems

Snubbers are frequently used in electrical systems with an inductive load where the sudden
Snubbers are frequently used in electrical systems with an inductive load where the sudden

interruption of current flow leads to a sharp rise in voltage across the current switching
interruption of current flow leads to a sharp rise in voltage across the current switching

device, in accordance with Faraday's law. This transient can be a source of electromagnetic
device, in accordance with Faraday's law. This transient can be a source of electromagnetic

interference in other circuits. Additionally, if the voltage generated across the device
interference in other circuits. Additionally, if the voltage generated across the device

is beyond what the device is intended to tolerate, it may damage or destroy it. The snubber provides
is beyond what the device is intended to tolerate, it may damage or destroy it. The snubber provides

a short-term alternative current path around the current switching device so that the inductive
a short-term alternative current path around the current switching device so that the inductive

element may be discharged more safely and quietly. Inductive elements are often unintentional,
element may be discharged more safely and quietly. Inductive elements are often unintentional,

but arise from the current loops implied by physical circuitry. While current switching
but arise from the current loops implied by physical circuitry. While current switching

is everywhere, snubbers will generally only be required where a major current path is
is everywhere, snubbers will generally only be required where a major current path is

switched, such as in power supplies. Snubbers are also often used to prevent arcing across
switched, such as in power supplies. Snubbers are also often used to prevent arcing across

the contacts of relays and switches and the electrical interference and welding/sticking
the contacts of relays and switches and the electrical interference and welding/sticking

of the contacts that can occur. RC snubbers
of the contacts that can occur. RC snubbers

A simple snubber uses a small resistor in series with a small capacitor. This combination
A simple snubber uses a small resistor in series with a small capacitor. This combination

can be used to suppress the rapid rise in voltage across a thyristor, preventing the
can be used to suppress the rapid rise in voltage across a thyristor, preventing the

erroneous turn-on of the thyristor; it does this by limiting the rate of rise in voltage
erroneous turn-on of the thyristor; it does this by limiting the rate of rise in voltage

across the thyristor to a value which will not trigger it. An appropriately-designed
across the thyristor to a value which will not trigger it. An appropriately-designed

RC snubber can be used with either DC or AC loads. This sort of snubber is commonly used
RC snubber can be used with either DC or AC loads. This sort of snubber is commonly used

with inductive loads such as electric motors. The voltage across a capacitor cannot change
with inductive loads such as electric motors. The voltage across a capacitor cannot change

instantaneously, so a decreasing transient current will flow through it for a small fraction
instantaneously, so a decreasing transient current will flow through it for a small fraction

of a second, allowing the voltage across the switch to increase more slowly when the switch
of a second, allowing the voltage across the switch to increase more slowly when the switch

is opened. Determination of voltage rating can be difficult owing to the nature of transient
is opened. Determination of voltage rating can be difficult owing to the nature of transient

waveforms, and may be defined simply by the power rating of the snubber components and
waveforms, and may be defined simply by the power rating of the snubber components and

the application. RC snubbers can be made discretely and are also built as a single component.
the application. RC snubbers can be made discretely and are also built as a single component.

Diode snubbers
Diode snubbers

When the current flowing is DC, a simple rectifier diode is often employed as a snubber. The
When the current flowing is DC, a simple rectifier diode is often employed as a snubber. The

snubber diode is wired in parallel with an inductive load. The diode is installed so
snubber diode is wired in parallel with an inductive load. The diode is installed so

that it does not conduct under normal conditions. When the external driving current is interrupted,
that it does not conduct under normal conditions. When the external driving current is interrupted,

the inductor current flows instead through the diode. The stored energy of the inductor
the inductor current flows instead through the diode. The stored energy of the inductor

is then gradually dissipated by the diode voltage drop and the resistance of the inductor
is then gradually dissipated by the diode voltage drop and the resistance of the inductor

itself. One disadvantage of using a simple rectifier diode as a snubber is that the diode
itself. One disadvantage of using a simple rectifier diode as a snubber is that the diode

allows current to continue flowing for some time, causing the inductor to remain active
allows current to continue flowing for some time, causing the inductor to remain active

for slightly longer than desired. Circuit designs must consider this delay in the dropping-out
for slightly longer than desired. Circuit designs must consider this delay in the dropping-out

of the actuator. The diode must immediately enter into forward
of the actuator. The diode must immediately enter into forward

conduction mode as the driving current is interrupted. Most ordinary diodes, even "slow"
conduction mode as the driving current is interrupted. Most ordinary diodes, even "slow"

power silicon diodes, are able to turn on very quickly, in contrast to their slow reverse
power silicon diodes, are able to turn on very quickly, in contrast to their slow reverse

recovery time. These are sufficient for snubbing electromechanical devices such as relays and
recovery time. These are sufficient for snubbing electromechanical devices such as relays and

motors. In high-speed cases, where the switching is faster than 10 nanoseconds, such as in
motors. In high-speed cases, where the switching is faster than 10 nanoseconds, such as in

certain switching power regulators, "fast", "ultrafast", or Schottky diodes may be required.
certain switching power regulators, "fast", "ultrafast", or Schottky diodes may be required.

More sophisticated solid-state snubbers In some DC circuits, a varistor or two inverse-series
More sophisticated solid-state snubbers In some DC circuits, a varistor or two inverse-series

Zener diodes may be used instead of the simple diode. Because these devices dissipate significant
Zener diodes may be used instead of the simple diode. Because these devices dissipate significant

power, the relay may drop-out faster than it would with a simple rectifier diode. An
power, the relay may drop-out faster than it would with a simple rectifier diode. An

advantage to using a transorb over just one diode is that it will protect against over
advantage to using a transorb over just one diode is that it will protect against over

voltage with both polarities, if connected to ground, forcing the voltage to stay between
voltage with both polarities, if connected to ground, forcing the voltage to stay between

the confines of the breakdown voltages of the Zener diodes. A Zener diode connected
the confines of the breakdown voltages of the Zener diodes. A Zener diode connected

to ground will protect against positive transients to the value of the Zener breakdown, and will
to ground will protect against positive transients to the value of the Zener breakdown, and will

protect against negative transients greater than a normal forward diode drop.
protect against negative transients greater than a normal forward diode drop.

In AC circuits a rectifier diode snubber cannot be used; if a simple RC snubber is not adequate
In AC circuits a rectifier diode snubber cannot be used; if a simple RC snubber is not adequate

a more complex bidirectional snubber design must be used.
a more complex bidirectional snubber design must be used.

Mechanical systems
Mechanical systems

Controlling pipe movement with mechanical snubbers
Controlling pipe movement with mechanical snubbers

Snubbers for pipe and equipment are used to control movement during abnormal conditions
Snubbers for pipe and equipment are used to control movement during abnormal conditions

such as earthquakes, turbine trips, safety/relief valve closure. Snubbers allow for free thermal
such as earthquakes, turbine trips, safety/relief valve closure. Snubbers allow for free thermal

movement of a component during regular conditions, but restrain the component in irregular conditions.
movement of a component during regular conditions, but restrain the component in irregular conditions.

A hydraulic snubber allows for pipe deflection under normal operating conditions. When subjected
A hydraulic snubber allows for pipe deflection under normal operating conditions. When subjected

to an impulse load, the snubber becomes activated and acts as a restraint in order to restrict
to an impulse load, the snubber becomes activated and acts as a restraint in order to restrict

pipe movement. A mechanical snubber uses mechanical means to provide the restraint force.
pipe movement. A mechanical snubber uses mechanical means to provide the restraint force.

See also Transient voltage suppression diode
See also Transient voltage suppression diode

Mechanical snubber References
Mechanical snubber References

Horowitz & Hill, Paul & Winfield. The Art Of Electronics, 2nd Ed. Cambridge University.
Horowitz & Hill, Paul & Winfield. The Art Of Electronics, 2nd Ed. Cambridge University.

p. 53. ISBN 0-521-37095-7.
p. 53. ISBN 0-521-37095-7.