What is a 12-pulse transformer?
A 12-pulse rectifier uses two 6-pulse rectifiers in parallel (12 diodes) to feed a common DC bus. A transformer with one primary and two secondary windings creates a 30 degree phase shift between the two current waveforms, which eliminates the 5th and 7th harmonics and reduces current THD to between 10 and 15 percent.
What is difference between 6-pulse and 12-pulse?
12 pulses means that on the basis of the original 6-pulse rectification, a set of 6-pulse rectifiers is added at the input end and after adding the phase-shifting transformer, so that the DC bus current is completed by 12 thyristors, so it is also called 12-pulse rectification.
What is 6-pulse and 12-pulse converter?
A 3-phase, full-wave rectifier is a 6-pulse device. The phase angle between successive secondary voltages is 120 deg. In a 12-pulse converter, the phase-shifting transformer converts the 3-phase input to 6-phase voltages, which when rectified, produce 12 ripples in the dc output voltage.
What is 24 pulse transformer?
Phase-shifting transformers are placed in front of four variable frequency drives operating on a 480 V system, resulting in a 24-pulse cancellation. The current is very similar to the voltage and has a very low distortion level.
What is a pulse transformer?
Pulse Transformers are designed to transfer pulses (signals/voltage with a rapid rise time, a duration of constant signal/voltage, and then a rapid fall time) from one side of a circuit to another.
What is the advantage of twelve or multi Bridge pulse converter?
The advantages of Twelve pulse converter are obvious. The ripple content of the ac voltage superimposing the mean value of the dc voltage is reduced greatly. The value of g increases (0.988) effectively improving the power factor.
How does pulse number affect harmonics?
A further increase in the number of pulses to 24, achieved by using two parallel twelve-pulse units with a phase shift of 15 degrees, reduces the total harmonic current to about 4.5%.
What is harmonics in VFD drives?
Harmonic Distortion is a measure of the amount of deviation from a pure sinusoidal wave form that can be caused by a non-linear load (a VFD is considered a non-linear load because it only draws current from the power line as required).
What are the advantages of 12 pulse converter?
Where are pulse transformers used?
The pulse transformers can operate at high frequencies, and can transfer more power as compared to a normal transformer of the same size. Pulse transformers are widely used for low power circuits, high power switched mode power supplies, and signal transmission.
What are the advantages of pulse transformer?
Its high voltage resistance makes it practical for large scale operations. More Windings With more than two windings, pulse transformers utilize several transistors at the same time. It helps limit phase shifts or delays. Less turns equates to less resistance and more power.
What is pulse number of a converter?
Pulse Number The pulse number of a converter is defined as the number of pulsations (cycles of ripple) of direct voltage per cycle of alternating voltage. The conversion from AC to DC involves switching sequentially different sinusoidal. voltages onto the DC circuit.
What is a 12-pulse VFD?
Unlike standard 6-pulse VFDs, which contain six diodes, 12-pulse VFDs contain two separate, parallel 6-pulse bridges in the input converter of the VFD. These additional pulses smooth out the waveform, making it more sinusoidal and generating less harmonic distortion to be distributed through your power system and ultimately returned to the utility.
Can I operate several 12-pulse systems on a common 12-pulse transformer?
Not permitted: Operation of several 12-pulse systems on a common 12-pulse transformer The operation of several 12-pulse systems on a common 12-pulse transformer (see figure below) is not permitted. This can cause balance currents, which can result in a blown fuse or even damage (e.g., thyristor damage).
What is the recommended EMF value for a 12-pulse parallel connection?
Note For a 12-pulse parallel connection, we recommend to switch over the method of calculating the EMF calculation for the armature current precontrol to p50162 = 4 (EMF calculated from the speed actual value).
What is the difference between 12-pulse and 18-pulse variable frequency drives?
Here, we take a look at two veterans in the harmonic mitigation field: 12-pulse and 18-pulse variable frequency drives (VFDs). Unlike standard 6-pulse VFDs, which contain six diodes, 12-pulse VFDs contain two separate, parallel 6-pulse bridges in the input converter of the VFD.