3-phase uncontrolled rectifier - difference of 2 version circuits

Hi,

I'm going though a trainer manual for our power electronics lab experiments. I'm at 3-phase uncontrolled rectifier section and the experiment provided two versions of circuits. This one:



The second circuit is common on Google images but the first one is different and I tried to find one and understand what the use of it but didn't find any.

Could you explain what is circuit 1 and what is the use of it ?

Here's the manual introduction of it:

The uncontrolled B6U six-pulse bridge is used for rectification of 3phase alternating voltage.
This circuit provides maximum idealized DC voltage, as the respective pair of diodes (V1 + V4,
V3 + V6, V5 + V2) takes over flow of current at the commutation moment. Order of diode passage
is given by the sequence of voltage rise. For easier comprehension the B6U circuit can be
composed of two M3U circuits (see pic. 2.4.0.0).

Click to expand...

I understood from the quote that circuit 1 is a way to explain circuit 2. But is circuit 1 a practical circuit or it's just for explanation purpose ?

Here's a copy of the manual in the attachment, page 67.

The way #1 is drawn, no current ever flows in v4 v6 v2. It would help if it were to show where a load is attached.

Wire N seems to be a common as used in 'star' configuration. The common is absent in #2 but that's because it's unnecessary in some cases.

BradtheRad said:

The way #1 is drawn, no current ever flows in v4 v6 v2. It would help if it were to show where a load is attached.

Wire N seems to be a common as used in 'star' configuration. The common is absent in #2 but that's because it's unnecessary in some cases.

Click to expand...

The load in #1 is across Ud1, if you browse the manual, you'd notice that most the time load is a resistor or resistor/coil and they are just connected at the end of the circuit. In this case it's mostly across Ud1.

The first schematic has a practical use because it provides independent bipolar supplies (positive and negative, as referenced to the common wire). The labels and arrows don't go far enough in making this clear.

My simulation emphasizes it by having loads attached. (Green is positive polarity, red is negative.) It shows how to make full use of the entire cycle.

One load can be different from the other, or absent. The common wire carries current and is necessary in this case.

BradtheRad said:

The first schematic has a practical use because it provides independent bipolar supplies (positive and negative, as referenced to the common wire).

Click to expand...

oh ... well that's impressive and interesting !

at this level of providing DC voltages, so the output isn't smoothed. Are there types of loads that would get benefit of this un-smoothed voltages or there has to be some sort of smoothing/regulating ?

Regular brushed DC motors can run fine without any smoothing.

Yes, absolutely that's specific application. Because if we mention other types of motors, then they run on different types of voltages.


Here are my conclusions about running different types of motors:
1. Servo motors, run differently with PWM which is way different than the type of voltage which is used to run brushed DC motors.
2. Also, stepper motors run with pulsating pattern of voltages.
3. I think DC brushed motors can also run on a wider range of voltages, they can be run with PWM, unregulated DC voltages and regulated DC voltages.

Are my conclusions right ?

Yes,
And if you select a series wound brushed motor, they can also run from AC.