Control Precis 3 Flashcards by Black Maskers

What are the limiting factor for HYDRAULIC power systems over Electric power systems?

Limiting factor:

Safe pressure that pipes, valves and pistons can withstand
10 x up on electrical systems (using magnetic fields)

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Why is OIL used for HYDRAULIC systems and not AIR?

Oil is practically incompressible, transmits forces better than air

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How can you alter the rate of flow on a hydraulic system without altering the pump flow rate?

Using a FLOW RELIEVE VALVE

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What hydraulic device is needed to provide BI-Directional control for the motor?

2 way spool valve

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What changes must be made to the BENT AXIS MOTOR to change its speed?

Axis ANGLE = Speed

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What changes must be made to the BENT AXIS MOTOR to change its flow rate?

Axis ANGLE = Flow rate

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Can a SWASH PLATE PUMP act as a motor?

YES, it can act as both a pump and a motor

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Draw a OPEN LOOP HYDRAULIC CIRCUIT ?

P5-13 (Figure. 2)

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Describe the functions of a (VDP) VARIABLE DISPLACEMENT PUMP in the open loop hydraulic circuit?

The angle of the block can be controlled
Zero angle = Zero flow
Greater angle = greater the O/P
Direction flow can be controlled

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Describe the functions of a CONSTANT SPEED MOTOR in the open loop hydraulic circuit?

AC motor with enough torque to maintain constant speed to the VDP(variable displacement pump)

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Describe the functions of a FORCE TORQUE MOTOR in the open loop hydraulic circuit?

Type of SOLENOID
Vary the current will vary the movement
Its attached to the swash plate (VDP), which will change the ANGLE changing the amount of flow

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Describe the functions of a RESERVOIR AND BOOST PUMP in the open loop hydraulic circuit?

one way valves only allows oil to be taken from the tank

- Boost pump used to slightly pressure low pressure line to avoid CAVITATION

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What is CAVITATION?

Oil moving from HIGH pressure areas to LOW pressure areas too quickly can form BUBBLES. When the bubbles POP at very high pressures it causes damage and CAVITATION on the system

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Draw a ELECTRO-HYDRAULIC POSITIONAL SERVO

P5-20 (Figure. 10)

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What 6 parts make up a HYDRAULIC POWER SYSTEM and draw it in a DIAGRAM?

P5-16 (Figure. 6)

Constant speed motor
Constant delivery pump
Pressure control valve
Accumulator (smoothing circuit)
Filter
Reservoir

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What is the function of the ACCUMULATOR in the hydraulic power system?

To SMOOTH out any PRESSURE fluctuations from the pump

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How is the HYDRAULIC POWER SYSTEM used in the MLRS?

Used to supply AZIMUTH and ELEVATION
Pump compensator controls the pressure
Oil cooled in HEAT EXCHANGER

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Explain the workings of a ELECTRO-HYDRAULIC SERVO VALVE?

Servo VALVE is controlled by a MAGNET with 2 attracting COILS on opposite ends
The FLAPPER is in the centre of the VALVE (where there is no SPOOL movement)
If the MAGNET is pulled to one of the COILS using a voltage, the SPOOL will either move LEFT/RIGHT
Which will determine the direction of flow for the controlled motor

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ELECTRO-HYDRAULIC SERVO VALVE?

Advantages:

Disadvantages:

Advantages:

Uses system FEEDBACK
High ACCURACY

Disadvantages:

Expensive

POWER TRANSMISSION BY GEAR TRAIN

Torque Formula?

Torque formula:

I/P torque = O/P torque X (O/P speed // I/P speed )

POWER TRANSMISSION BY GEAR TRAIN

Speed Formula?

Speed Formula:

O/P speed // I/P speed = Product(X) I/P gears teeth // Product(X) O/P gears teeth

What type of gear would you use IOT have a I/P shaft at 90 degrees to your O/P shaft

worm and worm wheel

What is BACKLASH in gears normally referred to?

And how is it overcome?

DEAD ZONE (space) between contact of gears

Using SHIMS or TENSION springs

Name 2 types of OPTICAL SHAFT ENCODERS?

Incremental type

- Absolute type

What do these two types of OPTICAL SHAFT ENCODERS usually measure? Incremental Disc: Absolute Disc:

Incremental type: - Shaft VELOCITY - Direction Absolute type: - Shaft angular POSITION - Elevation

What is meant by a 10 bit GREY code on a ABSOLUTE disc?

Resolution of the disc: More bits = higher the resolution 4 bits: 2 to the power of 4 = 16 (unique codes) divided by the disc (360 degrees) Accuracy= 22.5 degrees

What is the main deciding factor to using GREY Code over BINARY Code on an ABSOLUTE disc?

BINARY code: - Can be out by 180 degrees if the LEDs don’t line up correctly GREY code: - At MAX can only be out by 22 degrees if the LEDs dont line up

Convert BINARY to GREY 00110 01110 GREY to BINARY 00101 01001

``` Using XOR gate 00=0 10=1 01=1 11=0 ``` BINARY to GREY 00110 - 00101 01110 - 01001 GREY to BINARY 00101 - 00110 01001 - 01110

Name 2 types of LINEAR POWER SUPPLY systems

- Zener Shunt circuit | - IC Differential amplifier circuit

Draw the ZENER SHUNT STABILISER circuit? P7-2 (Figure. 3)

P7-2 (Figure. 3)

What Mathematical expression describes a ZENER SHUN circuit?

Vin = ( Izmin + IL )R + Vz Izmax = P / V

What are the main DISADVANTAGES for a ZENER SHUN circuit ?

- I/P must be higher than O/P - High power loss - Poor regulations

Draw a IC DIFFERENTIAL AMP circuit? P7-7 (Figure. 7)

P7-7 (Figure. 7)

Linear Power supplies Advantages: Disadvantages:

Advantages: - Reliable - Low maintenance - Low cost Disadvantages: - Runs hot - Low efficiency 50%

Switched MODE POWER SUPPLY ? Advantages: Disadvantages:

Advantages: - High efficiency 80% - Runs cooler Disadvantages: - Noise (due to inductor)

How can we overcome the NOISE of the Inductors when using SMPSU (switched mode power supply units)?

- Filtering (electrical filters) - Screening (inclosed box) - Earthing

Draw a Simple PWM(pulse width modulator) And describe the PRINCIPLES of the SMPSU (switched mode power supply unit)? P7-9 (Figure. 9)

P7-9 (Figure. 9)

On a SMPSU (switched mode power supply unit) What is the function of the inductor?

To Produce a back EMF for the capacitor to slowly discharge

Draw a PWM(pulse width modulator) DEVICE used on the Challenger MBT? P7-13 (both)

P7-13 (both)

Draw the Astable Multivibrator circuit used on the Challenger MBT? P7-14 (Figure. 2)

P7-14 (Figure. 2) - When ( Vo > +20V ) circuit swaps to Neg (-) - When ( Vo > -20V ) circuit swaps to Neg (+) - Circuit repeats this process to produce a constant WAVE o/p Voltage

What drives the Generators field windings using the PWM o/p?

The CLASS-D Amplifier

How does a CLASS-D amplifier operate?

Either - Operated OFF (non conducting) - Operates ON (fully conducting) - 95% efficiency

What is the main POWER supply Unit we use in the Mill?

FEPS (Field Electrical Power Supply) - 8KW - 16KW - 40KW - 50hz and 60hz

What type of load sharing capabilities does the FEPS use?

- Master and Slave (up to six generators) | - Operates on the same Freq and Voltage Phase angle together

Draw a VOLTAGE DOUBLER circuit? P7-27(Figure. 5)

P7-27(Figure. 5)

Draw a H BRIDGE Amplifier circuit? P7-28(Figure. 6)

P7-28(Figure. 6)