What Is a Pulsed DC?

Current or voltage pulses that appear repeatedly in a period are called pulse currents, and they appear in the same direction or in positive and negative alternating directions. The pulsed current obtained from the alternating current through rectification is also called "pulsating DC current" and "pulsating DC voltage". ^[1]

Pulse current is also called pulsating current, which means the current with constant direction and constant intensity. Strictly speaking, the current output by a DC generator is a pulsating current. It's just that the magnitude of this change in current intensity is small. ^[2]

Charge a set of parallel pulse capacitors and discharge the test object in the same way (such as the shunt or high-capacity capacitor fuse discharge). The peak value of the lightning pulse current can reach 200,000A, and the time for the waveform to reach the peak value is 8s. The 50% value time is 20 s. The following figure shows the actual connection method and the equivalent circuit of the capacitor discharging through the test object.

During the discharge of the pulsed power to the drive coil, a large pulsed current of tens of kiloamperes or even tens of kiloamperes will be generated. Commonly used high current measurement methods include shunt method, optical method, Hall effect method and Rogowski coil method. In recent years, researchers have explored new technologies for pulsed high-current testing such as electro-optic and magneto-optical methods. These methods have also been applied in practice. Their advantages are less intervention in the measured object, but the complexity of the system is greatly increased. The reliability of the test depends on the actual performance of the optical and electronic systems. Under relatively special conditions, it is still constantly developing.

Pulse current medicine

The pulse current acts on the human tissue through the milli-needle, which significantly changes the ion concentration and distribution in the tissue, thereby affecting the human tissue function. The low-frequency pulse current is called dense wave (high frequency) with a fast frequency, generally 50 to 100 times / second; the slow frequency is called sparse wave (low frequency), usually 2-5 times / second. Different waveforms and frequencies have different therapeutic effects, and an appropriate waveform should be selected according to the condition.

Dense wave: It has an inhibitory effect and can reduce the function of nerve stress. It is often used for sedation pain, relief of spasm, acupuncture anesthesia, etc.

Sparse wave: The excitatory effect is more obvious, which can cause muscle contraction, increase ligament tension, and delay the inhibition of perceptual nerves and motor nerves. It is often used to treat palpitations and soft tissue injuries.

Dense waves: Sulfur waves and dense waves appear alternately for 1.5 seconds each. The excitatory effect is dominant, and it has analgesic effects, promotes blood circulation and exudate absorption. It is often used for pain syndromes, sprains and contusions, periarthritis, facial paralysis, and muscle weakness.

Intermittent wave: A dense and intermittent wave that is intermittent and intermittent. It can increase the excitability of muscle tissue and is often used to treat paralysis.

Sawtooth wave: It is a undulating wave whose pulse amplitude automatically changes according to the zigzag shape. The frequency is close to the human breathing frequency. It can be used for artificial electric breathing, and can increase the excitability of nerve muscles, improve blood circulation, and promote the absorption of exudates. ^[6]

Pulse current welding

In molten electrode gas shielded welding, a pulsed arc provides an intermittent, periodic, and high-peak pulse power to the welding circuit through a special pulse power supply device, thereby generating an electromagnetic force proportional to the square of the pulse peak current. At the same time, it also significantly increases the plasma flow force. And periodically apply a large current to a small-dimensional arc current such as a short-circuit arc to make it a mandatory jet transition. Pulse current welding can also save energy. Due to the unique device of pulse power and the application of base current and peak current, it is possible to achieve a jet transition arc state for some low current welding materials that can only be used in short circuit arcs. For example, pulse welding of thin plates can not only achieve high-speed welding, but also obtain better quality welds and more reliable welding structures. ^[7]

Pulse current

Pulse current electrolytic processing can be divided into sine wave or rectangular wave, low frequency (tens of Hz) or high frequency (kHz ~ tens of kHz), wide pulse (ms ~ tens of ins), narrow pulse ( Dozens of buckets to hundreds of buckets) and ultra-short pulse (BS level) and other types. According to the cooperation mode of its feed and power supply, it can be divided into three types: continuous pulse current and continuous feed; periodic pulse current and periodic feed; continuous pulse current and pulse synchronous vibration feed.

Early pulse current electrolytic machining was mainly based on low-frequency, wide-pulse, periodic pulse current, periodic feed or synchronous vibration feed mode. The processing technology level of this mode is obviously improved compared with the traditional DC electrolytic processing, and has been applied locally. In the 1990s, the mode of continuous high-frequency, narrow pulse current and continuous feed was developed, and further breakthroughs were made in the processing technology of profiles and cavities. After a lot of experimental research and preliminary trial production applications, it has shown obvious Technical and economic effects and important application prospects. In recent years, research on nanosecond ultra-short pulse electrolytic etching processing technology has been carried out, which has opened up a new research direction of micro electrolytic processing. ^[8]

Pulse current pulse current sintering

Pulsed current sintering is sometimes referred to as "electric spark sintering" or "plasma activated sintering", which is a new method for preparing metals, ceramics, and organics by passing current through the sample. Porous materials can be prepared by controlling pressure, temperature, and direct current pulses. The short sintering time and fast temperature rise of pulse current sintering are the two major advantages of preparing porous materials. In addition, it can also prepare new porous materials including metastable materials and compounds that are easily decomposed by heating. The sintering mechanism of pulse current sintering is not clear at present, and the properties of porous materials prepared by this method have not been widely studied. ^[9]