Dorofeyev Viktor

FACULTY: ELECTROTECHNICAL

Speciality: Electromechanics systems of automation and electrical drive

Theme of master's work: "Synthesis diagnostics apparatus of controlled rectifier"

Leader of work: Valeriy Matveevich Shymyatskiy

ABSTRACT

SYNTHESIS OF LOGICAL SWITCHING DEVICE

Sometimes rotating direction needs a change when electric drive works. For this reversing method exist. From one-sided conduction of thyristors reversing thyristor rectifier can be obtained using two sets of irreversing thyristor rectifiers. At that each of the groups will define only one direction.
The control of reversing thyristor rectifiers can be realized in two way:
1. joint
2. separate
The separate control consist in control pulses feed on one thyristor group, at the same time second group is closed. It is completely exclude passing of equating current.
It should be noted that a new element LSD (logical switching device) is appearing in the circuit.
Logical switching device makes such functions:
1. The choice of group for work depending of sign control voltage it is the difference of assigning voltage and feedback voltage.
2. Exclusion of opening standing group in the presence of a current in working group and taking down control pulses from the working group when current flows through it.
There are circuits of LSD in which used:
1. two conductivity sensors
2. one conductivity sensor
The circuit with one conductivity sensor is used.

Figure 1 √ diagram of drive working in backspacing and state table.

The algorithm of work of LSD is:
Б1 (t + 1) =f[i, ΔU, Б1t ]
Б2 (t + 1) =f[i, ΔU, Б2t ]
b1, b2 is control signals of blocking first and second thyristor groups. May be 0 or 1. Zero is absence of blocking. One is blocking.
Б1 (t + 1), Б2 (t + 1) is control signals of blocking first and second thyristor groups for the next moment of time.
Synthesis of LSD can be made:
Plotting the diagrams of changing input signals when reversing is made or during the increase of speed with recuperation. On the diagram (figure 1) analog quantities are marked with capital letters and digital quantities are marked with small letters.

Б1(t+1) =Δu i Б1t + Δu i Б1t + Δu i Б1t + Δu i Б1t

On the figure 1 in this table suitable points on the state diagram are located in columns and the state of suitable parameters is located in lines on.

б1(t+1) = [(ΔU + ΔU) i +ΔU i ] б1t + ΔU i б1t = ( ΔUi + ΔUi +ΔUi + ΔUi ) б1t

_ _ _ _ _ _ _
ΔU i б1t = (i + ΔU) б1t + ΔU i б1t = (ΔU i ) б1t + ΔU i б1t

Figure 2 √ logical circuit LSD with one conductivity sensor

Working circuit LSD was made in environment of Matlab (figure 3a). The signals of current I and error ΔU is feeding the entries of LSD which is got from the diagram of drive working in reversing. The state of these signals is depending on verity table. Output signals of LSD are defining with state of RS trigger. The structural model of RS trigger is represented on figure 3b. The entry of the trigger KK realizes a function of permitting the work (signal ⌠1■) and the prohibition of the work (signal ⌠0■) of the trigger. This is an imitation of the work operators.
Results of the work of modeled circuits of LSD are represented on the oscillogram (figure 4). This results show that modeled circuit of LSD replies to the technological requirements which are set to the control system of reversing of thyristor rectifier.

a) b)
Figure 3 √ The structural model of: Ю) LSD, b) RS trigger

Figure 4 √ The oscillogram working LSD

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