Clamping voltage is defined as the maximum voltage that is allowed to pass through an electrical circuit breaker or surge protector before further voltage is prevented from passing through the circuit. Clamping voltage techniques are used in modern electrical equipment to protect against power surges.

The clamping voltage is the default voltage for the surge protector. A surge protector will prevent the input voltage from exceeding this number. Note that a surge protector is a device connected to a circuit to protect downstream devices from spikes or surges in AC circuits.

If the input voltage is higher than this preset “clamping voltage”, the surge protector will clamp the voltage down to this preset (safe) voltage.

Therefore, protect the device(s) from experiencing power surges, which may damage the device and endanger the safety of bystanders. If the voltage is suppressed in this way, the voltage is said to be “clamped”.

For example, the nominal voltage of the device is 120V and it works fine at 240V input voltage range.

If the input voltage exceeds this limit, the device may be damaged. For better operation of the device, we choose a clamping voltage lower than the maximum sustained voltage.

In this example, the maximum sustained voltage is 240V. To prevent a surge effect in a device, a surge protector is connected to a device that limits the input voltage to a little less than 240V. Here, we select the clamping voltage as 220V.

If there is an upstream surge that causes the voltage to increase, the surge protector will “clamp” the voltage to a maximum of 220V.

The performance of surge protectors is tested in laboratories, and many tests are performed on them.

Clamping Voltage vs Breakdown Voltage:

The breakdown voltage is defined as the minimum voltage level at which the insulator starts to behave as a conductor and a large current flows through the insulator.

The electrical characteristics of a diode are between that of an insulator and a conductor because diodes are made of semiconductor materials such as silicon, germanium, etc.

Under reverse bias conditions, the diode behaves as an insulator. If the supplied voltage is greater than the reverse breakdown voltage, breakdown occurs at a junction, and current flows through the diode.

Clamping voltage is a different concept from breakdown voltage. A clamping voltage is a baseline beyond which the input voltage cannot go. The breakdown voltage is the baseline at which the current is zero. After crossing this baseline, current begins to flow.

Clamping Voltage vs Let Through Voltage:

Clamping voltage is also known as “let-through voltage”. In some surge protector devices, refer to the clamping voltage as the let-through voltage.

As the name suggests, this is a voltage level up to which the surge protector allows through connected devices. And up to this voltage level, connected devices work properly.

Good Clamping Voltage:

The value of the clamping voltage for a particular device or circuit depends on how much voltage it can withstand.

A surge protector is used to control the surge generated by the input supply. The clamping voltage decides the voltage level at which the surge protector reduces the surge. For the best surge protector, the clamping voltage is not more than 400V.

For a good surge protector, response time against surges is paramount. Speed up response time, speed up protection. Typically, the response time of surge protection is measured in nanoseconds.

A lower value of clamping voltage indicates better protection. But sometimes, this results in unnecessary tripping and a short life for the entire safety system.

Guarantors Labs (UL) suggests three degrees of assurance for 120 V AC frameworks, and these are at the 330 V, 400 V, and 500 V voltage levels. The standard clasping voltage for a 120V AC framework is 330 V.