SU1198719A1 - Device for emergency braking of d.c.electric drive - Google Patents

Description

The invention improves the reliability of emergency braking of a direct current electric drive due to the fact that the latter consists of a series-connected rectifier, an armature winding of an electric motor, an excitation winding and a current sensor, and the armature winding is stitch ^ and is connected by a thyristor (T) of a dynamic braking speed sensor an electric motor whose output is under ”keys to the input of the quad, the output connected to one of the inputs of the multiplication unit, the other input of which is under * * keys to the output of the driver (ф, signal of the magnetic flux input connected to the current sensor output, the output of the multiplication unit is connected to one of the comparator inputs, the other input of which is connected to the setpoint unit, and the Comparator output through the inverter and the disconnecting contact of the relay is connected to the control electrode T, while the quadr power inputs , the multiplication unit, F, the setpoint unit, the comparator and the inverter are connected to the output of the power source, in parallel to the input of which a relay is connected, and parallel to the output is a capacitor. 1 il.

to .5 At a ”1198719

one

1198719

2

The invention relates to electrical engineering and can be used in DC drives.

The purpose of the invention is to improve the efficiency and reliability of emergency braking of the drive.

The drawing shows the functional scheme of the device for emergency braking of the electric drive.

A device for emergency braking of a permanent electric drive; ka contains a series-connected rectifier 1, armature winding 2 and motor excitation winding 3, diode 4 connected parallel to the excitation winding and dynamic braking thyristor 5 parallel to the armature winding, excitation winding current sensor 6, motor rotation speed sensor 7, relay 8, a capacitor 9 and a power source 10, parallel to the input of which a relay 8 is connected, parallel to the output — a capacitor 9, as well as a quad 11, a setpoint block 12 and a serially connected signal conditioner 13 are magnetic The multiplication unit 14, the comparator 15 and the inverter 16, the power inputs of which are connected to the output of the power source 10, the output of the current sensor 6 and the output of the rotational speed sensor 7 are connected to the inputs of the magnetic flux signal generator 13 and quadr 11, respectively. connected to the inputs of the multiplication unit 14, the output of the setpoint unit 12 is connected to the input of the comparator 15, and

: output of the inverter 16 through the disconnecting contact 17 of the relay 8 is connected to the controlled electrode of the thyristor 5 of the dynamic braking.

Device for emergency braking of the DC drive operates as follows.

In case of a sudden disconnection of electric energy, the voltage at the output of the rectifier 1 becomes equal to zero. The energy stored in the inductance of the excitation winding, creates a current flowing in a closed loop: the excitation winding 3 - diode 4. The magnitude of the magnetic flux Φ _in generated by the current flowing through the excitation winding 3 is equal to

νν ^t ®,

ten

15

20

where f _o is the magnetic flux at the initial moment of emergency braking;

C ¹ - time;

T ⁼ - - time constant winding? excitement 3;

- inductance of the excitation winding 3;

Kv - resistance of the excitation winding 3.

At. the introduction of the delay on the thyristor 5 dynamic braking magnetic flux at the time of the thyristor is equal to

’.-½.

^τθ , And

where C "delay time.

When the thyristor 5 of the dynamic braking is closed, a current flows through the winding 2 of the armature of the electric motor,

the maximum value of which 1 „

I shmh

equals

^ 3.

²⁵ g _ SF _in and>. SF _about e ^Τ 8 _ω

"Chtah" · about ^with - g> - ·> (3)

where K i - the resistance of the armature of the electric motor;

30 С - electric motor constant;

and) - the frequency of rotation of the electric. engine

Therefore, 1 _Yatas with unchanged motor parameters (s, K ^, T _c ) is proportional to the product. By changing the delay time 1h for switching on the thyristor 5 of the dynamic braking, it is possible to change years from ₄₀

The magnitude of armature current and 1 x _LGpL motor speed ω is necessary to restrict the conditions for switching to prevent torsion ₄ $ traction fire.

At the same time, for the same motor when changing from 0 to nominal - ω and the armature current from 0 to

2.5 nominal value of production ₅₀

^I1 ! MG ^{No. p5BA} ·

Substituting (3) into (4) we get

SF _th <Yeh * ^1s ^ ^tv

(? "

ίϊ)

So, as for the same engine s, E _i , T _{and the} values are constant,

55

1198719 4

then (5 1 can be brought to the following form:

, (6)

Where

Solving (b) with respect to the delay time, we get:

Λ ₃ = Τ _β ? Ή (cf _of p) ^g ). 48).

Therefore, by introducing the delay time according to (8), it is possible to limit the current at an acceptable level in the emergency braking mode at the nominal speed and ensure emergency braking at frequency-, rotational speeds below the nominal speed. The coefficient of proportionality K is calculated by expression (7).

In case of a sudden disconnection of electrical energy, the voltage at the input of the power supply source 10 also becomes zero, de-energized, the relay 8 connected in parallel with the input of the power supply 10, closing its contact 17.

The power of the quadr 11, shaper 13 of the magnetic flux signal, multiplication block 14, setpoint block 12, comparator 15 and inverter 16 is carried out by the energy stored in capacitor 9. The output signal from sensor 7 goes to quadr 11, the output voltage of which is, and

= K ^ ² , (9)

where · is the conversion factor;

and> - rotational speed.

The signal from the output of the current sensor 6 is supplied to the driver of the magnetic flux signal 13, the voltage and _g at the output of which is. ,

and ₂ = k ₂ f _in , (y)

where k _? - conversion factor.

Signals ϋ ₂ and and. arrive at block 14 multiplication, the voltage ϋ ₃ at the output of which is equal to

^and e = k, k ₂ Φ _βω ζ (11)

Next, the signal is fed to the first input of the comparator 15, and to the second input is a signal ϋ ₄ from the output of the setpoint block 12

and ₄ = K ₃ -A, (12)

where K ₃ - coefficient proportional- '

nosti.

When and, ί and _{4, the} output of the comparator is zero. When P ₃ > and _{4, the} signal takes the maximum value. Then it is inverted in the inverter '

5 16, at the output of which the signal takes the maximum value at ϋ ₃ Ζ υ ₄ ·

Since the output of the inverter 16 is connected to the control electrode of the thyristor 5 dynamic braking

10 at the time of a sudden power outage, i.e. when closing

• contact 17 of relay 8, until ϋ ₃ > and ₄ , dynamic braking thyristor 5 is closed and opens

15 when performing

and ₄ - (13)

Substituting (2) into (11), (11) into (13) and (12) into (13), we obtain

20 ll,

⁸ ω = κ ₃ (and).

or

25

thirty

35

I

If you choose

K _l K _g _ s K ₃ A · “K _Y A '

(? 6)

then the dynamic braking thyristor 5 is switched on after a sudden deactivation of electrical energy after a time determined by the dependence (8 1.

Claims (1)

Claim A device for emergency braking of a direct current electric drive, comprising a series-connected rectifier, an armature winding of an electric motor and a motor winding, and . A diode is connected parallel to the excitation winding 45, and a thyristor of dynamic braking is connected in parallel to the armature winding, which is distinguished by the fact that, in order to increase efficiency and reliability 50 emergency braking, entered into it the excitation winding current sensor, motor speed sensor, relay, capacitor and power supply, parallel to the input? 55 of which a relay is connected, parallel to the output — a capacitor, as well as a quad, setpoint unit and series-connected driver 1198719 of the magnetic flux signal, multiplication unit, comparator, and inverter, the power inputs of which are connected to the output of the power source, the output of the excitation current sensor and the output of the rotational speed sensor connect. The yens with the inputs of the magnetic flux signal shaper and the quadr, respectively, whose outputs are connected to the multiplication block inputs, the output of the setpoint unit are connected to the comparator input, and the output of the inverter is connected to the control electrode of the dynamic braking through the break contact of the relay.