SU649118A1 - Ac machine excitation winding protection arrangement - Google Patents

Description

The proposed device is intended for excitation systems for AC electric machines that have a reversible exciter on controlled vents. In sup.1, a variety of excitation systems for synchronous compensators and asynchronized synchronous machines with current reversal, two-group reversing converters with separate control are used. A device for separate control is known, it is contained 1, its separate control unit associated with control circuits of valve groups 1. However, such a device does not protect the excitation winding of the AC machine during a transitional mode of operation of the machine. It is also known a device for securing the excitation windings of an AC machine, which contains a single-group converter and a protective element 2. The device does not provide all the operating modes of the reverse excitation system during a transient operating mode of the machine. The closest technical solution to the technical essence and the achieved positive effect is a device for protection of the excitation winding of an AC machine, excited from a controlled two-group valve converter with an automatic excitation controller, containing a separate control unit connected to the control group of valve groups, protective elements connected in parallel to the field winding 3. In a known device, protective elements are connected at a design value of the current uzhdeni that causes an increase in protective elements installed moaiyusti n venti.chnyh groups reversible converter. The aim of the invention is to reduce the installed power of the clamping elements and valve groups of the reversing converter. This is achieved by the fact that the device for protection of the winding of the excitation of a non-transitory current excited from an uglyuvanny two-group valve reversing converter with an automatic excitation regulator containing a separate control unit associated with control circuits of the valve groups, protective elements connected in parallel to the excitation winding are provided current sensors of protective elements, with the outputs of current sensors of protective elements being connected to the inputs of the separate control unit, and as safety x elements used controlled valves connected antiparallel to the field winding.

In order to reduce the installed power of the valve groups of the reversing converter, the device is equipped with a reversible current sensor included in the excitation winding circuit, forcing unlocking pulses of protective elements, logic circuits AND, OR-NOT and OR, and the output of the reversible current sensor is connected to the zero-organ input, the first and second outputs of the zero-organ through the first and second circuits OR are connected to the control circuits of the valve groups and to the OR-NOT circuit, the output of which is connected to one input of the AND circuit, the second input of which is uzhit for connection to the output drive automatic regulator, the output of AND gate circuits connected to the OR gate pulse shapers and protective devices are connected to the respective outputs of the zero-body.

The drawing shows the structural electrical circuit of the proposed device. It contains valve groups B and BZ, which form a reversible transducer with counter-parallel connection, corresponding systems 1 and 2 of pulse-phase control, reversible current sensor 3, through which the OV excitation winding is connected to the reversing transducer terminals, automatic excitation regulator 4, unit 5 separate control units 6 and 7 lock valve groups, voltage sensors 8 and 9 on the valves, null organ 10, AND 11 element, OR-NO 12 element, protective elements 33j and ZEG, sensors 13 and 14 of protective element current , shapers 15 and 16 unlocking pulses of protective elements, elements OR 17 and 18.

The proposed device works as follows.

In the absence of forced disturbances in the field winding from the stator side of the machine, the valve groups are switched by a separate control unit 5 using the locking units 6, 7. The separate control unit operates as a control signal from the automatic controller 4 and from the voltage sensors 8 and 9 on the valves. The control signal of the excitation controller 4 through the element 11 is passed to the control circuits 1, 2. In steady state at the output of the null organ 10 and current sensors 13,

14, the signal is absent, and at the output of the element OR-NO 12 there is a signal that is applied to the second input of the element 11 and thereby ensures the passage of the control signal from the regulator 4 through the element 11.

In a transient mode of operation of the machine, when the flow of the excitation current can be interrupted through a previously working group. For example, when the first valve group B is operating, counter-emf occurs, i.e. the field winding current starts to flow in the opposite direction against the conductivity of the valves Bj. Counter current (EMF) this group is closed, interrupted

current flow begins to increase the voltage of the same polarity. At a predetermined voltage level, the actuating element 33j is switched on from the autonomous starting system, closes the reverse polarity for Bj and limits the voltage at a predetermined

level The signal of the presence of current through the protective element 33i comes from the current sensor 13 to the separate control unit 5 and locks the control Bj and opens the Br. The field winding current is closed through the protective element GE and

valve group B. If the signal from the regulator 4 puts Bj into the rectifying mode, then 13g takes on the field winding current and counter-voltage disconnects the protective element GE.

If the signal from the regulator 4 switches BJ to the forcing mode (closed group), then Br is transferred to the inverter mode (Bi and Bg are controlled by voltages of different polarity) and produces a long field of the excitation winding. After npeKpanie, the flow of current through the field winding is turned off and the BI is turned on using a separate control unit. The signal for switching the valve groups comes from the controller 4 or from the current sensors of the protective elements.

When the second valve group is operating

BJ and the occurrence of counter-emf current flows in the opposite direction, the protective element ZEg from the autonomous launch system is turned on. The signal of the current sensor of the protective element ZE blocks the control Bg and switches on B. The field winding current is closed through the Zeg and Bj. Further operation mode of the proposed device is determined by the signal of the automatic controller.

Claims (3)

1. USSR author's certificate No. 199974, M.KL.2 N02R 13/16, 29.07.67. 2. USSR author's certificate No. 390621, M.KL.2 N02NZ / 18, 07.09.70. 3.Technical report No. 12-67.64 "Testing of a static thyristor reversal excitation system of a KSV-50000/11 synchronous compensator at the Pakhra Mosenergo substation, VNIIE, Energosetproekt, state registration number 70042390, 1970.