SINGLE
PHASE SEMI CONVETER DRIVE
In before post we learnt about the DC series motor torque and
armature voltage equations, by using the DC series motor now we convert the AC
signal to DC signal. To reveal the phenomenon read the below content.
* The circuit diagram for single phase semi converter drive
which is feeding with the DC series motor is given below:
* The circuit diagram consists of 5 semiconductors in which 2
thyristors and 2 diodes along with the freewheeling diode.
* when the AC supply is fed to the semi converter circuit the
thyristors and diodes together acts and converts the AC signal to DC signal
which is fed to the series motor consists if internal resistance Ra and
internal inductance La.
* For positive half cycle of the AC supply the power
travelling direction is given as e(+) - T1 - Df - Ra - La - eb - D2 - e(-).
*For negative half cycle the power direction is given as e(-) - D1 - Df - eb - T2-
e(+)
*Due to the presence of unidirectional devices it is unable
to reverse the direction of the current.
*Due to the presence
of freewheeling diode there exists a continuous current mode operation without
falling zero.
Wave forms:
The below wave forms are belongs to the semi conductor drive
circuit which is fed to DC series motor.
*The above wave forms shows the circuit operation mode. when
the AC supply is given to the circuit, the circuit activates and starts
conducting with an firing angle α .
* For period α < ωt < π, the motor voltage is equal to
supply voltage.
*
For period π < ωt < α, the motor terminals are shorted through Df making
Ea zero.
*
Beyond π period, the emf of the armature reverses the input voltage by changing
polarity, this leads the freewheeling diode Df to conduct.
*
During π to π+α period the freewheeling diode recovers the energy from the
inductance ( storage element) and is supplied to load in the form of kinetic
energy (Mechanical energy).
*
Due to the presence of Df the torque developed in the motor is said to be
continuous.
* The torque and speed characteristics are given below:
* The torque and speed characteristics are given below:
SINGLE
PHASE FULL CONVERTER DRIVE
The full converter drive is a rectifier which rectifies the
AC signal into pulsated DC signal without changing the frequency.
The basic circuit diagram of single phase full converter is
visualized in the below figure.
* The full converter consists of completely 4 semi conductors
in which 4 of them are thyristors named T1, T2, T3, T4 from the circuit diagram.
* when the circuit is fed with the AC supply the thyristors
converts the AC signal into DC signal and later fed to the DC series motor
which is connected to it with internal resistance Ra and inductance La.
* For positive half cycle conversion the current flow
direction in the circuit is given as e(+) - T1 - Ra - La - eb - T3 - e(-).
* For negative half cycle conversion the current flow
direction is given as e(-) - T4 - eb - La - Ra - T2 - e(+).
* The circuit is fed with the AC supply which is time-variant
in nature. The armature voltage and current (Ea and Ia) is depends upon the
operation conditions.
wave form operation:
The below wave forms are belongs to single phase full
converter fed with the DC series motor:
* When the circuit is fed with the AC supply the thyristors
get activated and starts conducting with an firing angle α
* For positive half cycle of AC supply the current travelling
direction in the circuit is e(+) - T1 - Ra - La - eb - T3 - e(-).
* For negative half cycle of AC supply the current travelling
direction in the circuit is e(-) - T2 - Ra - La - eb - T1 - e(+).
* In full converter T1 and T3 are triggered at firing angle α and thyristor T2 and T4 are
triggered at π+α
* Thyristor T1 and T3 conducts during the interval α < ωt < π+α
Thyristors
T2 and T4 conducts during the interval π+α < ωt < α.
Due
to the presence of unidirectional semi conductors there is no chance to reverse
the direction of current.
* The torque and speed characteristics are given below:
* The torque and speed characteristics are given below:
Thanks for this useful post. we highly appreciate your hardwork.
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thanks bro , post 3-phase semi converter connected to dc series motor torque expression
ReplyDeleteExplanation is wrong the above circuit t1 and t2 are on and current passes through those thyristor
ReplyDeleteWorst 👎👎👎 explanation because of you my time is wasted