EXPLANATORY NOTE

TO COURSE WORK

discipline “Electric drive”

SUSU – 140400.2015.336. PZ KR

Head ______________ V.I. Romanov ____________________2014 | |

The author of the project is a student of the group 336-Ozz D.O.Ushakov _____________________2014 | |

The work is protected with an assessment of ______________ V.I. Romanov ____________________2014 |

Ozersk 2014

ANNOTATION

Ushakov D.O. – Automated electric freight elevator. – Ozersk: SUSU, 2015, 64 p., ill., bibliogr. list – 5 name.

In this course work, the following tasks are considered: the choice of the type of electric drive, the choice and verification of the electric motor, the choice of a power converter for powering the engine, the choice of component equipment and the development of a circuit diagram of the power part of the electric drive, the choice of a power transformer, the calculation of transformer parameters, the choice of a smoothing reactor.

TABLE OF CONTENTS

INTRODUCTION ………………………………………….. ………………………………….. nine

1 Selecting the type of drive ………………………………………………. …………….. eleven

2 Selecting and checking the electric motor……………………………………………. …. fourteen

2.1 Calculation of the load diagram of the mechanism……………………………………….. 14

2.2 Motor pre-selection …………………………………………………. . sixteen

2.3 Calculation of the motor load diagram……………………………………….. 20

2.4 Checking the engine but heating ……………………………………….. …….. 25

3 Selection of a power converter for powering the motor, selection of component equipment and development of a circuit diagram of the power part of the electric drive………………………………………………….. …. 27

3.1 Selection of a complete thyristor drive ………………………… 30

3.2 Selecting a power transformer……………………………………………………… …. thirty

3.3 Calculation of transformer parameters……………………………………….. 31

3.4 Choice of smoothing reactor……………………………………………………… ….. 32

3.5 Schematic diagram of the power section ………………………… 33

4 Mathematical model of the power part of the electric drive …………… 35

4.1 Calculation of the parameters of the power part of the electric drive in absolute units …………………………………………………….. …………………………………………. ……………………….. 35

4.2 Choice of basic values of the system of relative units ………………………… 37

4.3 Calculation of the parameters of the power part of the electric drive in relative units …………………………………………………….. …………………………………………. …………… 38

4.4 Calculation of transducer gains …………………………………………………….. 40

5 Selecting the type of drive control system……………………………………….. 42

6 Calculation of the control part of the armature current loop ………………………………………. 45

6.1 Calculation of the parameters of the mathematical model of the current circuit …………… 45

6.2 Structural calculation of the EMF sensor and compensation link …….. 49

6.3 Structural design of the current controller ………………………………………. 52

7 Calculation of the control part of the speed loop ………………………………………. 56

7.1 Calculation of the parameters of the mathematical model of the speed loop …. 56

7.2 Structural calculation of the control part of the speed loop 57

8 Calculating the ramp-function generator……………………………………………………… ……. 60

8.1 Calculation of the parameters of the mathematical model of the intensity generator 60

8.2 Structural calculation of the ramp-function generator ………………………… 61

BIBLIOGRAPHICAL LIST………………………………………………………… ….. 64

Introduction

A modern electrified mechanism is considered as an electromechanical automated (or generally automatic) system closed by feedback (through an operator or a special technical device) to control the fundamental technical parameters.

An electric motor is necessarily present in the main (power) channel, and converters of electrical and mechanical energy can also be presented. With their help, specific laws of electromechanical energy generation are implemented. Control channels for various functional elements of the power circuit, as well as feedback channels, are part of the automatic control system (ACS) of the electric drive.

New production equipment for modern mechanized production is being created by the joint efforts of mechanical engineering technologists, specialists in electrical machines, electric drives and automation. Simultaneously with the development of technology and the structural composition of mechanical equipment, its electrical equipment is being developed.

The design and kinematic features of the executive body of the mechanism are largely predetermined by the type of drive, which is guided by when developing the mechanical part.

The reverse also takes place – depending on the design solutions of the mechanical part, the electric drive undergoes a significant change. Design solutions are reflected in the parameters of the mechanical and electrical circuits of a single electromechanical system. The ratios of the latter affect not only the static and dynamic qualities, but also the consumption of electricity, the efficiency of the electrified mechanism.

1 SELECTING THE TYPE OF DRIVE

When choosing an electric drive system and the type of current, first of all, the operating condition of the production mechanism is taken into account. High productivity and product quality can only be ensured with proper consideration of the static and dynamic characteristics of the drive and the working machine. The kinematics and even the design of the working machine are largely determined by the type of electric drive used, and, conversely, depending on the design features of the actuator, the drive undergoes significant changes.

When choosing the type of electric drive, the following should be taken into account: the nature of the static moment; required speed control limits; smoothness of regulation of the required mechanical characteristics, starting and braking conditions, number of starts per hour, environmental quality, etc.

Initially, the issue of choosing a regulated or unregulated type of EP is decided. In the latter case, the task is greatly simplified. It all comes down to choosing an AC motor (induction motors). In the case of speed control, the issue of AC or DC drive is solved.

The use of direct current can be justified only in cases where the drive must provide increased requirements for smooth control of the nature of transients. DC drives are used in mechanisms operating in intermittent modes: cranes, lifting mechanisms, auxiliary mechanisms of the metallurgical industry (schleppers, roller tables, pushers, pressure devices) and, in particular, planers.

In the case of intermittent drives, it is determined from the conditions for obtaining the minimum duration of the transient process, the minimum dynamic moments. For this purpose, either special motors with a minimum moment of inertia are used, or they are switched to a two-motor drive (the total moment of inertia of two motors of the same power as a single-motor drive is 20-40% less).

According to the protection against environmental influences, open, protected, closed and sealed motors (JP44) protect against splashes from any direction inside. Dust, moisture and gases have access to such engines. When choosing engines, it is necessary to take into account the fact that, with the same power and speed, closed engines have the largest masses, dimensions and cost.

For the electric drive of a freight elevator, it is possible to use the following ED:

– “TPCh-AD” (thyristor frequency converter – asynchronous motor);

– “G-D” (generator – engine);

– “TP-D” (thyristor converter – motor).

The TFC-AD system, in principle, makes it possible to obtain characteristics similar to those of TP-D, but the cost of a thyristor frequency converter is much higher than a controlled rectifier.

The disadvantages of the G-D system include:

– the need for a double conversion of energy (from electrical energy of alternating current to mechanical, and from mechanical again to electrical direct current, regulated voltage), which leads to a significant decrease in efficiency;

– the presence of two machines in the converter unit, the installed power of each, if we neglect the losses in the machine, is equal to the installed power of the regulated movement;

– significant dimensions and weight of the installation. The need for a foundation for the converter unit;

– high capital and operating costs;

– in order to force transient processes, it becomes necessary to use an increased (several times u003d 2.5 – 4) voltage.

For the freight elevator electric circuit, we adopt the “TP-D” system with voltage reversal at the motor armature, it is possible to change the motor rotation in the reverse drive also due to a change in the direction of the current in the motor excitation circuit when a non-reversible controlled rectifier is used in the armature circuit. This circuit is simpler and cheaper than a two-set armature converter, but inferior in terms of dynamic performance due to the relatively large time constant of the excitation windings.

2 MOTOR SELECTION AND CHECK

2.1 Calculation of the load diagram of the mechanism

For a preliminary selection of the engine, we calculate the mass of the counterweight and construct the load diagram of the mechanism (the graph of the static loads of the mechanism). The calculation of the time of the cycle sections at the stage of preliminary selection of the engine is performed approximately, because until the acceleration and deceleration times can be determined (the total moment of inertia of the drive is unknown before the motor is selected).

Counterweight weight:

3700 kg

Active components of the moment of static resistance on the traction sheave:

11282 Nm

0 Nm

6769 Nm

-7897 Nm

Reactive components of the moment of static resistance on the traction sheave:

= -2234 Nm

1670 Nm

2008 Nm

1275 Nm

Moments of static resistance on the traction sheave:

9048 Nm (braking)

1670 Nm (motor mode)

8777 Nm (motor mode)

-6622 Nm (braking)

Angular speed of traction sheave:

0.652 1/s

Distance between floors:

6.667 m

Travel time when moving 3 floors (approximately):

67 s

Movement time when moving to 1 floor (approximately):

22 s

Cycle time (approx):

133 s

Parking time per floor (approx):

81 s

**Figure 1 –** View of the load diagram of the mechanism

2.2. Engine pre-selection

We focus on the choice of engine series , designed for nominal intermittent operation with 40%.

Equivalent static moment on the traction sheave during operation in the cycle (taking into account losses in gears):

7357.7 Nm

The influence of losses in transmissions is taken into account by substituting the values:

– in braking mode (signs of torque and speed are different);

– in motor mode (signs of torque and speed are the same).

5428.8 Nm

2783.3 Nm

14628.3 Nm

-3973.2 Nm

Estimated engine power:

4899 W,

where – safety factor (accept 1,2).

Choosing a series engine . The nominal data of the equivalent motor are given in table 1

Table – 1 Data of the selected engine D21

Parameter | Designation | Meaning |

Rated power, kW | 3.6 | |

Rated armature voltage, V | ||

Rated armature current, A | ||

Rated speed, rpm | ||

Maximum allowable moment, Nm | ||

Armature winding resistance (T=20 ^{o} C), Ohm |
0.66 | |

Winding resistance of additional poles (T=20 ^{o} C), Ohm |
0.28 | |

Moment of inertia of the motor armature, kg m ^{2} |
0.125 | |

Number of pole pairs | ||

Maximum allowable armature current ripple factor | 0.15 |

We accept a parallel connection of the anchors of two engines.

Let’s define equivalent data:

Rated power:

P _{N} =2× P _{N}

P _{N} u003d 2 × 3.6 u003d 7.2 kW

Moment of inertia:

J _{d} u003d 2 × J _{d}

J _{d} u003d 2 × 0.125 u003d 0.25 kg × m ^{2}

Rated speed:

_{nN} = _{nN} =1080

Maximum allowable moment:

M _{max} =2× M _{max}

M _{max} =2×90=180 Nm

Maximum allowable armature current ripple factor:

k1(additional)= k1(additional)=0.15

We connect the windings of two motors in parallel then,

rated armature voltage:

U iN _{u003d} U iN _{u003d} 220V

Rated armature current:

I iN _{u003d} 2 × I _{iN}

I iN _{u003d} 2 × 21 u003d 42A

Armature winding resistance:

R _{yao} u003d 0.5 × 0.66 u003d 0.33 Ohm

Winding resistance of additional poles:

R _{d.p} u003d 0.5 × R _{d.p}

R _{d.p} u003d 0.5 × 0.28 u003d 0.14 Ohm

Let’s make a table of the obtained equivalent parameters

Table – 2 data of the selected engine (2 * D21)

Parameter | Designation | Meaning |

Rated power, kW | 7.2 | |

Rated armature voltage, V | ||

Rated armature current, A | ||

Rated speed, rpm | ||

Maximum allowable moment, Nm | ||

Armature winding resistance (T=20 ^{o} C), Ohm |
0.33 | |

Winding resistance of additional poles (T=20 ^{o} C), Ohm |
0.14 | |

Moment of inertia of the motor armature, kg m ^{2} |
0.25 | |

Number of pole pairs | ||

Maximum allowable armature current ripple factor | 0.15 |

Series engine – uncompensated, with natural cooling and insulation class .

For further calculations, a number of data will be required that are not given in the reference book. Let’s calculate the missing engine data.

Motor armature circuit resistance, normalized to operating temperature:

0.65 ohm

where – coefficient of increase in resistance when heated to operating temperature ( = 1.38 for class isolation when recalculated from 20 ^{o} C).

Rated armature EMF:

192.7 V

Rated angular speed:

113.04 1/s

Motor design constant multiplied by rated flux:

1.7 Wb

Rated motor torque:

71.4 Nm

Engine idle torque:

7.7 Nm

Motor armature circuit inductance:

0.014 H,

where coefficient equals 0.2 for a compensated motor and 0.6 for an uncompensated one.

2.3 Calculation of the motor load diagram

To check the selected motor for heating, we will build a simplified load diagram of the motor (excluding electromagnetic transients). To build a load diagram, we will calculate the gear ratio of the gearbox, bring the moments of static resistance and operating speeds to the motor shaft, take the dynamic moment and acceleration of the electric drive, taking into account the overload capacity of the motor and the specified allowable acceleration.

Gear ratio:

173.4

The moments of static resistance, reduced to the motor shaft:

, for XY = 41, 12, 23, 34,

where – speed sign function:

= 1 – when lifting;

= -1 – during the descent.

23.6 Nm

23.7 Nm

92 Nm

-15.2 Nm

The total moment of inertia of the drive:

0.37 kg m ^{2} ,

where – coefficient taking into account the moments of inertia of the coupling halves and the gearbox (taken equal to 1.2).

Note: we believe that the moment of inertia does not depend on the mass of cargo in the cabin, so we substitute the mass of the nominal cargo into the formula.

The module of the dynamic moment of the engine according to the condition of the maximum use of the engine according to the overload capacity:

83.6 Nm,

where = 0.95 – coefficient taking into account the overshoot of the moment on the refined load diagram (built taking into account the electromagnetic inertia of the armature circuit);

– the maximum modulo static moment reduced to the motor shaft.

Motor shaft acceleration in transient modes:

225.9 1/s ^{2}

Elevator car acceleration:

0.6 m/s ^{2}

The acceleration of the elevator car is less than the maximum allowable.

We divide the load diagram into 16 intervals: 4, 8, 12, 16 – pause intervals; 1, 5, 9, 13 – acceleration intervals; 3, 7, 11, 15 – deceleration intervals; 2, 6, 10, 14 – intervals of work with a steady speed.

Duration of acceleration-deceleration intervals:

0.44 s

Cabin path during acceleration-deceleration:

0.066 m

The path of the cabin when moving 3 floors, traveled at a constant speed:

19.87 m

The path of the cabin when moving to the 1st floor, traveled at a constant speed:

6.538 m

Travel time at constant speed when moving 3 floors:

66.23 s

Time of movement at a constant speed when moving to the 1st floor:

21.79 s

Cycle time:

135.13s

Parking time per floor:

82.7 s

Engine torques at acceleration intervals:

– 60

107.3

175.6 68.4

Engine torques at deceleration intervals:

107.2

-59.9

8.4

-98.8

Engine torques at intervals of movement at a constant speed:

23.6

23.7

92

-15.2

Based on the results of the calculation, a load diagram and an engine tachogram are built (see figure – 2)

**Figure – 2** Tachogram and load diagram of the electric drive

freight elevator.

2.4 Motor temperature check

To check the selected motor for heating, we use the equivalent torque method. Using the load diagram, we find the moment equivalent in terms of heating during operation in the cycle. Then we bring the equivalent torque to the nominal duty cycle of the motor. For the normal thermal state of the engine, it is necessary that the equivalent torque reduced to the nominal PV be no more than the rated torque of the engine.

Equivalent moment for the time of work in a cycle (according to the load diagram):

44.85 Nm

Reduced to nominal duty cycle equivalent moment:

38.17 Nm

Since the condition performed ( 71.4 Nm), then the selected engine passes through heating.

Heating reserve:

46%

Stock more than 5%.

3 SELECTION OF A POWER CONVERTER DEVICE FOR POWERING THE ENGINE, SELECTION OF ACCESSORIES AND DEVELOPMENT OF THE BASIC ELECTRICAL SCHEME OF THE POWER PART OF THE ELECTRIC DRIVE

To ensure the required operating mode of the DC motor of independent excitation, discussed above, a two-set thyristor converter is used. Each set of TS is assembled according to a three-phase bridge circuit and the connection between the sets is carried out according to an anti-parallel circuit.

Two-set converters can be performed with joint and separate control of sets. With separate control of the sets, only one set of the converter always works, and control pulses are not applied to the thyristors of the second set. The mechanical characteristics of the electric motor fed from such a converter have non-linear sections, which is explained by the operation of the converter in the intermittent current mode. The intermittent current mode occurs at relatively small values of the load current, therefore, when the electric motor is operating with a large range of load torque changes and with frequent reverses, it is not advisable to use a two-set thyristor converter with separate control. However, the size of the zone of discontinuous currents can be significantly reduced by turning on the smoothing choke, but this will increase the inertia of the electric drive, and in a closed ED system, in order to ensure a given speed, it will be necessary to choose an uncompensated time constant smaller than in the absence of a smoothing filter. Value may turn out to be unrealistic. In addition, with separate control, a dead time of 5-10 ms is required. Therefore, for switching sets during current reversal, converters with separate control are used to power those mechanisms where, according to the conditions of the technological process, this pause is permissible. In converters with joint control of sets, both sets work simultaneously: one is in rectifier mode, the other is in inverter mode. An equalizing current flows between the sets. To reduce its value, equalizing chokes must be introduced into the converter. We accept separate control of thyristor converter sets for the EA. The scheme of the power part of the TP-D is shown in Figure – 3.

The main advantage of the bridge circuit in relation to the zero thyristor switching circuit in the converter is that it has twice the circuit pulse ( ), therefore, the amplitude of the variable component of the output voltage is smaller. This, in turn, will require a much lower inductance of the smoothing choke (reactor). In addition, a transformer must be used in the zero circuit, the secondary winding of which, connected in a “star”, will provide “0”.

**Figure – 3** Schematic diagram of the power part of the electric drive

3.1 Selection of a complete thyristor drive

We select a standard converter, which is part of the complete KTEU electric drive.

220 V

42 A

Accept:

KTEU – – ABVGD – UHL4

230 V

50 A,

where A = 2 is the number of engines;

B u003d 2 – transformer connection with the network;

Г = 1 – the main adjustable parameter: EMF or speed, single-part regulation;

D = 2 – the composition of the switching equipment: with a linear contactor, dynamic braking.

KTEU – 230 / 50 – 23212 – UHL4

3.2 Selecting a power transformer

Rated line voltage and rated line current of the valve windings of the transformer:

200 V

40.8 A

Type of transformer – TSP – 16 / 0.7-UHL4

Connection diagram of primary and secondary windings –Y/∆

Rated power – 14.6 kVA

Rated voltage of valve windings – 380 V

Rated line voltage of valve windings – 205V

Rated linear current of valve windings – 41 A

Short circuit losses – 550 W

Relative value of short circuit voltage – 5.2%

3.3 Calculation of transformer parameters

Transformation ratio:

0.54

Rated line primary current:

22.2 A

Transformer phase active resistance:

0.108 ohm

Active component of the short circuit voltage:

3.77%

Reactive component of short circuit voltage:

3.58%

Inductive reactance of the transformer phase windings:

0.103 ohm

Note: Resistance and are the sum of the resistances (respectively active and inductive) of the primary winding, reduced to the secondary circuit and the secondary winding in the equivalent circuit (Y/∆).

The inductance of the windings of one phase of the transformer:

0.329 10 ^{-3} H = 329 mH,

where, at a power supply frequency of 50 Hz, 314 1/s.

3.4 Choice of smoothing reactor

The inductance of the smoothing reactor is selected from the condition of limiting the armature current ripples at an acceptable level. The total inductance of the armature circuit should be:

,

where – EMF of the converter at , 277 V

(K _{e} is a coefficient depending on the converter circuit, for a three-phase bridge circuit K _{e} u003d 1.35);

– pulsation of the converter for a bridge three-phase TP circuit;

– coefficient of voltage ripple (for a bridge three-phase TP circuit);

– admissible armature current ripple factor;

= 0.07 – for engines of the 4P series.

= 0.15 – for engines of the D series.

– coefficient of rectified voltage (for a three-phase bridge circuit).

0.0030 H = 3 mH

As ,L _{i} =14 mH, then there is no need for a smoothing reactor.

3.5 Circuit diagram of the power unit

The composition of the complete thyristor EP includes:

– DC motor with tachogenerator and centrifugal switch (if necessary);

– TP for powering the armature of the electric motor, consisting of power thyristors and a cooling system, protective fuses, discharge and protective RLC circuits, SIFU, emergency mode isolation devices, fuse control and surge protection;

– TP for power supply of the excitation winding; power transformer or anode reactor;

– switching and protective equipment in DC and AC circuits (circuit breakers, line contactors, knife switches);

– smoothing reactor in the DC circuit (if necessary);

– dynamic braking device (if necessary);

– electric drive control system;

– a set of devices, instruments and devices that provide operational control, status monitoring and signaling of the electric drive.

Figure – 3 shows a schematic diagram of a reversible electric drive of the KTEU series for a current of up to 200 A. The thyristor converter TP, consisting of two built-in bridges VSF, VSB, is powered from the 380 network through the QF1 circuit breaker and the LF anode reactor (or TM transformer) . The DC side is protected automatically by the QF1 circuit breaker. Line contactor KM serves for frequent switching of the anchor circuit (if necessary), dynamic braking of the electric motor M is carried out through the contactor KV and the resistor RV. Transformer T1 and diode bridge V are used to power the excitation winding of the motor LM. The tachogenerator BR is excited from a separate node A-BR; There is also a power supply unit for the YB electromagnetic brake. The CS control system based on the operator’s signals from the PU control panel, the signal on the state of switching and protective devices received from the control units of these devices and the UUK and C signaling, the signal from the general control circuit of the SUTA process unit, the signal about the armature current and the excitation current received from points RS1, RS2, a signal about the voltage at the armature of the electric motor, taken from the potentiometer RP1, a signal about the speed generated by the tachogenerator BR, gives control signals to the SIFU, UUK and C and to the control panel PU. The unit for controlling switching equipment and signaling UUK and S, by the operator’s commands and a signal from the control system, turns on or off the QF1-QF3, KM, KV devices, and also provides an alarm about the status of these and other protective devices.

The reference and feedback signals in the control system are galvanically separated from external extended circuits or high-potential circuits. The CS control system through galvanic separators outputs to the SUTA the values of the necessary regulated parameters (speed, current, etc.). The UUK and S device receives signals from PU, sensors, SUTA through two-position galvanic separators and high-level voltage converters to low-level voltage used in the system. The UUK and C device generates two-position logical or contact signals to the control panel and to the SUTA: about the readiness of the electric drive for operation, the state of emergency and warning alarms, zero speed or reaching a certain specified speed, etc.

4 MATHEMATICAL MODEL OF THE POWER PART OF THE ELECTRIC DRIVE

4.1 Calculation of the parameters of the power part of the electric drive in absolute units.

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