We have structured the training modules in a very simple manner, please follow the module one by one and do not jump to the higher module without doing the earlier ones. That is do not shift to module 2, without completing the module 1 and so on.
Module 0
The Basics
The List of components used in Industry
We will learn about all of them, very simply, we will follow a simple methodology based on following:
a. What is the function of each device.
b. How does it work.
c. What input it requires to function
d. What output it gives and how to use this output.
If we analyse all these devices based on four questions above, then we will see how simple and quick it is to learn about these products. So we take one by one and restricts ourselves to less theory and more of practical understanding.
1. Motors:
Are two types; AC and DC.
AC Motors are two types : 1 Phase and 3 Phase.
Both the motors have stators and rotors
Stator would have stator windings which are connected to terminals for power connections.
Module 0
The Basics
Exercise 1
The first exercise is to know about electricity as used in Industry.
What does it mean when we say 3 Phase 415 VAC 50 Hz Power Source ?
What does it mean when we say 1 Phase 220 VAC 50 Hz Power Source ?
What does it mean when we say 24 VDC ?
[Power Plants, Generation, Transmission, Distribution, Transformers, Rectifiers]
Electricity is generated in power plants. You must have seen thermal power plants with those big smoking chimneys. You must have heard of Hydel (Hydro-Electric) power plants. They produce electricity by moving a big wheel called Turbine. In thermal power plants the coal is used to boil the water which provides the steam and this steam is used to run the turbine, in Hydel power plants the water is thrown from a height and falls on the turbine buckets to create a rotary motion. The rotary motion of turbine with related control system gives us 3 Phase 415 VAC 50 Hz electricity.
So now you know power plants, you know about generation....So the next thing is transmitting this produced electricity from power plant at remote place to near the user.
[Can you straight away transmit 415 VAC 3 Phase 50 Hz from power plant which could be kilometers away from the village where it is required ? What will happen if you try to do so ? We see that transmission from the source (Power Plants) is done at very high voltage, why ?]
This is where you must understand the importance of Power Transformers, those big poles which you see when you travel on highways, those big white & Red Insulators, the copper / Aluminium cables, the concept of power drawn, the power/voltage/current relationship.
Actually the power plant is the source and supplies the power as per user load requirement, if the load is more (higher power) then higher current is drawn and if the load is less lower current is drawn. This is explained as
Power supplied from source = Power used by user + Transmission Loss
Power Supplied from Source = 1.73 Vs * Is * Cos(Phi)
Power used by user = 1.73 Vu* Iu * Cos (theta)
Transmission Loss = Is * Is * Cable Resistance
(Where Vs, Is are source voltage and currents and Vu, Iu are user requirements)
So it is clear that if Voltage of the source is higher then transmission wire/cable will take low current and low transmission loss will be there thus increasing the efficiency. So the transmission from the power plant is actually done at 11 kV, 33 kV, 132 kV etc at a very high voltage not at 415 VAC, this reduces the current and thus minimized the transmission loss.
[But then How do we increase the voltage from 415 VAC 3 Phase 50 Hz to 132 kV 3 Phase 50 Hz ?]
By using step up transformer. [This will be near source]
[How do we decrease the voltage from 132 kV 3 Phase 50 Hz to usable 415 VAC 3 Phase 50 Hz ?]
By using step down transformer. [This will be near user]
So this way we get 415 VAC 3 Phase 50 Hz of desired power (Kw) at our factory. Sometimes the Electricity board gives us a connection of 11 kV (or 1.1 kV) for higher power requirements, in that case we have to install the step down transformer in our premises to reduce the voltage to 415 VAC 3 Phase 50 Hz.
This connection will have 4 wires, R Y B and Neutral (a separate Ground / Earth wire may be created at our end), the voltage between any two phases (RY or YB or BR) shall be 415 VAC and voltage between (RN, YN, BN) shall be 220 VAC. If we require any other voltage like 110 VAC or 48 VAC then we will have to use the step down transformer. In case we need to make a DC, we would need a rectifier circuit and we can derive 5 VDC, 24 VDC or 48 VDC or 110 VDC, depending on the DC voltage required by the equipment.
Q. How do we design a circuit to get 24 VDC 5 Amps, our source voltage is 415 VAC ?
It is very simple, first we know that 415 VAC (any two phase RY or YB or BR) is the RMS voltage in case of sinusoidal wave form, so the peak voltage shall be 1.41 * 415 VAC = 585 VAC. This peak is actually roughly the DC peak value. So our transformer should have a peak secondary voltage of 24 VAC to get 24 VDC. So transformer step down ratio should be 585/24, that is 415 / 17. So we need around 17 VAC at the output of transformer. Now the second part is 5 Amps, so we simply multiply 24 VDC * 5 Amps = 120 VA, so we ask for a transformer of 415 Primary / 17 Secondary and 120 VA. We connect a full bridge rectifier as available in the market of 120 VA. This is the rough calculations to give an idea about getting DC voltage. To smoothen the same we use filter capacitors.
Exercise 2
[Pl proceed to exercise #2 only if you have scored 8 out of 10 in Exercise 1, this is not exam for marks this is for learning and gaining skills]
The second exercise is to know about all the components, instruments and devices used in the Industry. This exercise is more than the theoretical exercise, because an already experienced person would know the practical use of many of the items listed below, the fresh engineers will immediately recall once they encounter these products once they start working, alternatively you can choose our paid training program in which all these components will be physically demonstrated to you for better understanding.
The first exercise is to know about electricity as used in Industry.
What does it mean when we say 3 Phase 415 VAC 50 Hz Power Source ?
What does it mean when we say 1 Phase 220 VAC 50 Hz Power Source ?
What does it mean when we say 24 VDC ?
[Power Plants, Generation, Transmission, Distribution, Transformers, Rectifiers]
Electricity is generated in power plants. You must have seen thermal power plants with those big smoking chimneys. You must have heard of Hydel (Hydro-Electric) power plants. They produce electricity by moving a big wheel called Turbine. In thermal power plants the coal is used to boil the water which provides the steam and this steam is used to run the turbine, in Hydel power plants the water is thrown from a height and falls on the turbine buckets to create a rotary motion. The rotary motion of turbine with related control system gives us 3 Phase 415 VAC 50 Hz electricity.
So now you know power plants, you know about generation....So the next thing is transmitting this produced electricity from power plant at remote place to near the user.
[Can you straight away transmit 415 VAC 3 Phase 50 Hz from power plant which could be kilometers away from the village where it is required ? What will happen if you try to do so ? We see that transmission from the source (Power Plants) is done at very high voltage, why ?]
This is where you must understand the importance of Power Transformers, those big poles which you see when you travel on highways, those big white & Red Insulators, the copper / Aluminium cables, the concept of power drawn, the power/voltage/current relationship.
Actually the power plant is the source and supplies the power as per user load requirement, if the load is more (higher power) then higher current is drawn and if the load is less lower current is drawn. This is explained as
Power supplied from source = Power used by user + Transmission Loss
Power Supplied from Source = 1.73 Vs * Is * Cos(Phi)
Power used by user = 1.73 Vu* Iu * Cos (theta)
Transmission Loss = Is * Is * Cable Resistance
(Where Vs, Is are source voltage and currents and Vu, Iu are user requirements)
So it is clear that if Voltage of the source is higher then transmission wire/cable will take low current and low transmission loss will be there thus increasing the efficiency. So the transmission from the power plant is actually done at 11 kV, 33 kV, 132 kV etc at a very high voltage not at 415 VAC, this reduces the current and thus minimized the transmission loss.
[But then How do we increase the voltage from 415 VAC 3 Phase 50 Hz to 132 kV 3 Phase 50 Hz ?]
By using step up transformer. [This will be near source]
[How do we decrease the voltage from 132 kV 3 Phase 50 Hz to usable 415 VAC 3 Phase 50 Hz ?]
So this way we get 415 VAC 3 Phase 50 Hz of desired power (Kw) at our factory. Sometimes the Electricity board gives us a connection of 11 kV (or 1.1 kV) for higher power requirements, in that case we have to install the step down transformer in our premises to reduce the voltage to 415 VAC 3 Phase 50 Hz.
This connection will have 4 wires, R Y B and Neutral (a separate Ground / Earth wire may be created at our end), the voltage between any two phases (RY or YB or BR) shall be 415 VAC and voltage between (RN, YN, BN) shall be 220 VAC. If we require any other voltage like 110 VAC or 48 VAC then we will have to use the step down transformer. In case we need to make a DC, we would need a rectifier circuit and we can derive 5 VDC, 24 VDC or 48 VDC or 110 VDC, depending on the DC voltage required by the equipment.
Q. How do we design a circuit to get 24 VDC 5 Amps, our source voltage is 415 VAC ?
It is very simple, first we know that 415 VAC (any two phase RY or YB or BR) is the RMS voltage in case of sinusoidal wave form, so the peak voltage shall be 1.41 * 415 VAC = 585 VAC. This peak is actually roughly the DC peak value. So our transformer should have a peak secondary voltage of 24 VAC to get 24 VDC. So transformer step down ratio should be 585/24, that is 415 / 17. So we need around 17 VAC at the output of transformer. Now the second part is 5 Amps, so we simply multiply 24 VDC * 5 Amps = 120 VA, so we ask for a transformer of 415 Primary / 17 Secondary and 120 VA. We connect a full bridge rectifier as available in the market of 120 VA. This is the rough calculations to give an idea about getting DC voltage. To smoothen the same we use filter capacitors.
Register for paid Training to get the Exercise-1 Practical Question Set to assess your learning;
Exercise 2
[Pl proceed to exercise #2 only if you have scored 8 out of 10 in Exercise 1, this is not exam for marks this is for learning and gaining skills]
The second exercise is to know about all the components, instruments and devices used in the Industry. This exercise is more than the theoretical exercise, because an already experienced person would know the practical use of many of the items listed below, the fresh engineers will immediately recall once they encounter these products once they start working, alternatively you can choose our paid training program in which all these components will be physically demonstrated to you for better understanding.
It is suggested that each participant to make a list of all such Electrical, Electronics, Instrumentation, Automation components and products used in Industry and then tally the same with the list provided below..
Please scroll down only if you have made a list of your own with at least 20-25 components..
The List of components used in Industry
- 3 Phase AC Motors
- 1 Phase AC Motors
- AC Brake Motors
- AC Crane Duty Motors
- Star Connected AC Motors
- Delta Connected AC Motors
- DC Motors
- Gear Motors
- Gear Boxes
- Worm Gear Boxes
- Helical Gear Boxes
- Planetary Gear Boxes
- Pulleys and belts
- Timing Belts
- AC Drives
- DC Drives
- Dynamic Braking Resistors
- Programmable Logic Controllers
- Human Machine Interface
- Displays
- Multimeters
- Analog Voltmeter
- Analog Ammeter
- Analog Power Factor Meter
- Digital Meters
- Energy Meters
- Meters with communication capability
- Transformers
- Chokes
- Rectifers
- Transducers
- Contactors
- Over Load Relays
- MCBs
- MCCBs
- ACBs
- SFUs
- Current Transformers
- Proximity Switches
- Optical Sensors
- Color Sensors
- Limit Switches
- Encoders
- Load Cells
- Lugs
- Wires & Cables
- Manual Change Over Switches.
- Motorized Change Over switches.
- Push Buttons
- Selector Switches
- Power Supplies
- Power Factor Controllers
- Power Factor Capacitors
- Temperature Controllers
- Pressure Transmitters
- Counters
- Timers
- Sleeves
- Bus Bars
- Insulators
- Buzzers
- Mimics
- MCC Panels
- PCC Panels
- Distriution Panels
- APFC Panels
- Relays
- Protection Relays
For easy understanding we divide
the components in various Categories as follows.
- Electrical Power Distribution Products.
- Electro-Mechanical Transmission, Actuator Products.
- Electrical System Protection Products.
- Metering Products.
- Sensors, Transmitters, Transducers.
- Control & Monitoring Products.
Please
understand the above categories and as soon as you come across any product, you
should be able to immediately relate that product with the category.
- Electrical
Power Distribution Products.
MCB, MCCB, Air
Circuit Breaker, Vaccuum Circuit Breaker, Oil Circuit Breaker, Switch Fuse
Unit, Change-Over Switch, Power Transformers, Isolators, Fuses, Cables &
Conductors, Bus Bars,
[What is the
utility of these products?]. These products are required to
distribute the power from one point to another, circuit breakers act as
isolators also. They are power products, as their size and capacity will depend
on the level of current required to be transmitted. For example MCBs can be
from 2 Amps to 100 Amps in various combinations, MCCBs can be from 32 Amps to
1000 Amps in various comninations, ACBs can be from 400 Amps to 6300 Amps in
various combinations.
- Electro-Mechanical
Transmission, Actuator Products.
AC Motors, DC
Motors, Servo Motors, Hydraulic Motors, Gear Boxes, Worm Gear Box, Helical Gear
Box, Multi Stage Gear Box, Planetory Gear Box, Couplings, Pulleys, V Belts,
Clutch Brake, Magnetic Coupling, Fluid Coupling, Conveyors, Solenoid Valves,
Proportional Valves, Servo Valves, Pneumatic Actuators.
[What is the utility
of these products?]. Motors are generally required to convert
electrical energy into mechanical energy, thus giving motion to the systems.
Gear Boxes help in providing suitable speed and torques, Valves are required to
allow/block fluid flow, conveyors as driven by motors help in transporting
material from one place to another.
- Electrical
System Protection Products.
Over Current
Protection Relay, Under Voltage Protection Relay, Over Voltage Protection
Relay, Earth Fault Relay, Earth Leakage Relay, Over Temperature Protection
Relay, Reverse Power Protection Relay, Over Load Protection Relay, Phase Loss
Relay, Over Frequency Protection Relay, Under Frequency Relay.
[What is the
utility of these products?]. These products are required to protect
the Electrical System in case of any abnormality. They detect the abnormality
and generally take preventive steps like switching off/on the device etc.
- Metering
Products
Voltmeter, Ammeter,
Power Factor Meter, Frequency Meter, Energy Meter, Multi Function Meter, Flow
Meter, Tongue Tester, Humidity Meter, Conductivity Meter, pH Meter, Temperature
Meter, Pressure Meter, RPM Meter, Lux Meter.
[What is the
utility of these products?]. It helps to know the values of various
parameters like voltage, ampere, pressure, temperature etc on a display.
- Sensors,
Transmitters, Transducers.
Position Sensor,
Temperature Sensor, Pressure Sensor, Proximity Sensor, Limit Switch, Pressure
Switch, Temperature Switch, Encoder, Humidity Sensor, Current Sensor, pH
Sensor, Voltage Sensor, Power Sensor, Light Sensor, Mark Sensor, Distance
Sensor, LVDT, Thickness Sensor.
[What is the
utility of these products?]. Well, these are the probes, we know
about the physical conditions from them. They convert the physical parameters
into electrical signals for further use by controllers. Imagine, can we read
the temperature directly ? No we need thermocouple or RTD for that. Canw e read
the pressure directly ? No we need a diaphragm which when pressed will give
electrical signal.
- Control &
Monitoring Products.
Contactors,
Relays, MCBs, Temperature Controller, Pressure Controller, Humidity Controller,
Programmable Logic Controller, AMF Controller, Scanners, Data Acquisition
Systems, HMI, Supervisory Control & Data Acquisition System.
[What is the
utility of these products?]. They are the brain. They collect
information from the sensor products and control the physical parameters or
just display them for monitoring purpose.
a. What is the function of each device.
b. How does it work.
c. What input it requires to function
d. What output it gives and how to use this output.
If we analyse all these devices based on four questions above, then we will see how simple and quick it is to learn about these products. So we take one by one and restricts ourselves to less theory and more of practical understanding.
1. Motors:
Are two types; AC and DC.
AC Motors are two types : 1 Phase and 3 Phase.
Both the motors have stators and rotors
Stator would have stator windings which are connected to terminals for power connections.
For 3 Phase Motors there will be 3 windings and for 1 Phase Motors there will be 2 windings. Please understand the various parts as shown in the picture and also refer to the complete motor image as shown in the right side product list.
The idea is you make the connection to stator winding, it induces rotating magnetic field in the air gap between stator and rotor, and rotor starts moving as per Electro-Magnetic Induction principle. The load is connected to the rotor shaft by pulleys or gear boxes.
Now as made clear that a 3 - Phase motor has 3 windings, so it is important to understand what that means. There are two possible connections Star connection (Y) or Delta Connections.
The windings are u1u2, v1v2 and w1w2. They are self explanatory with their connection details to be done in terminal box of the motor. Where L1,L2 and L3 represents the power connections (R Y B ).
We can run the motor in star connections as well as Delta connections depending on what is written on the name plate of the motor, name plate of the motor is the specification sheet and if we understand we are through.
This is a very simple name plate sufficient to give some idea. It shows that if winding is connected in Delta then 3 Phase 400 VAC to be given, but if winding is connected in Star then 690 Volts to be given
[Can you analyse the circuit as given in the windings above to understand this 690 from 400 ?]
Then it gives the full rated current as 29/17 Amps, it talks of Kw and RPM as 1430 U/Min.
[Q. Now what is U/Min or RPM ?]
It is basically the rotor rotations per minute. How do you calculate it ? You must have studied a simple formula that is RPM = 120 * f / p where f is the frequency of the power supply and p is number of poles. In our case f = 50 Hz and the number of pole is as per design of the motors. It could be 2P, 4P, 6P and 8 P etc. So for we can calculate as follows..
2P = 3000 RPM
4P = 1500 RPM
6P = 1000 RPM
8P = 750 RPM
Now the rotor will not move exactly at these values, it will move at less RPM due to slip and that is what creates the torque. So 1430 RPM of above name plate suggests that it is a 4 Pole motor.
[Now how do we calculate the Amp ?]
So, lets take a thumb rule for 415 VAC 3 Phase Motors
Rated Current = 1.5 * HP
This is the approximation and good enough for various selection as required for design of motor starters.
At the end of this you should know
[Stator, rotor, terminal connections, Star Connections, Delta Connections, RPM, Amp, Voltage, HP / Kw]
2. Gear Box
[Do we need speed reduction, if yes, why ?]
Gear Box is a mechanical device, generally used for speed reduction. They look as follows.
Gear Box Internal Cut Out, for a very simple gear box
So you can figure out that smaller wheel will rotate faster as compared to the bigger wheel depending on the number of teeth or diameter ration. So if motor is connected to smaller wheel, and load is connected to bigger wheel then you will get speed reduction.
[Q. In the Gear Box picture you see one shaft of smaller diameter then the other shaft. Why ?]
3. Gear Motor
The Motor is same, only thing is Gear Box comes factory fitted with the motor.
The advantage here is that, you can ask for your required rating and required RPM at the final output shaft from the manufacturer itself.
There are various types of Gear Boxes, helical Gear Box, Worm Gear Box, Multi stage Gear Box, Planetary Gear Box, Multi output Gear Box, Cast Iron Body Gear Box, Aluminium Frame Gear Box. Please google and know about them. The idea is to get different RPM at output shaft as per application / load requirement.
[ Q. Do you know the relationship between Power, Torque and RPM ? Are you aware of P=2pi*N*T ?]
Example - 1. Motor Connected with Load with Pulleys and V - Belt.
3. AC Brake Motor
The normal AC Motor shaft will have a brake, there is a manual release lever also as shown above. This brake is Electrically actuated, and separate connection is provided for the same. If you do not want Brake Motor then you can install Brake on the motor shaft also, as normally done in case of Elevator and Crane vertical motion motors.
[Q. What will happen to elevator or crane of Brake is not applied ?]
4. Motor Starters for 3 Phase 415 VAC Class AC Motor
This will cover many many items as listed below and will help you understand the Electrical Aspect of starting an AC Motor.
[DOL Starter, Star Delta Starter, AC Drive, Softstarter, MCB, MCCB, Contactor, OverLoad Relay, Push Buttons, Indication Lamps, Wire Size Selection, Contactor Selection, OverLoadrelay Selection, MCB Selection]
Starter is a circuit basically used to start a motor. The idea is to give 3 Phase 415 VAC supply (3 wires) to connect to the motor terminals. As soon as power supply is made on to these terminals, the motor would start rotating. So how do we give supply to these terminals.
Simplest of all is DOL starter, it requires an MCB (isolator) and a contactor and few Buttons. So we learn about these components..
MCBs
Generally used for protection and isolation. They are available from 2 Amps to 63 Amps, in 1P, 2P, 3P and 4P combinations. For 3 Phase AC motor we need 3P MCB of suitable rating. As discussed above a 3 Phase AC motor approximately takes 1.5 * Motor HP as the current, so if we have to start at 10 HP motor, we would need an MCB which can carry 1.5 * 10 = 15 Amps current, so we choose an MCB of around 25 Amps.
for example, in a 3P MCB (Bottom right), you see three terminals below and 3 terminals above, you can connect power to bottom 3 Terminals (R Y B) and when MCB is on the power comes on to upper 3 terminals. In case of any short circuit or fault MCB trips and power is isolated from the upper terminals.
The MCB tripping is based on thermal principle, bimetallic strips get heated up when more than specified current passes through them and the lever mechanism trips the MCB in such case.
[Q. What are the standard MCB current ratings ? Where do we use 1P or 2P or 4P MCBs ?]
Contactors
These are required to start stop the motors. In general they are available from 6 Amps to 1000 Amps in 3P and 4P configuration. For AC motors 3P are used of suitable rating, as discussed above a 10 HP motor would take around 15 Amps Current so we have to choose a contactor which is more than 15 Amps rating, let us say 18 Amps or 26 Amps.
Above are the typical images of a contactor. It has a power circuit and a control circuit, Power Circuit is for main motor Ampere / current flow, for example above contactor is of 110 Amps (See A110), Control part is required to actuate the contactor (A1 and A2 terminals as shown above).
The idea is you make the connection to stator winding, it induces rotating magnetic field in the air gap between stator and rotor, and rotor starts moving as per Electro-Magnetic Induction principle. The load is connected to the rotor shaft by pulleys or gear boxes.
Now as made clear that a 3 - Phase motor has 3 windings, so it is important to understand what that means. There are two possible connections Star connection (Y) or Delta Connections.
The windings are u1u2, v1v2 and w1w2. They are self explanatory with their connection details to be done in terminal box of the motor. Where L1,L2 and L3 represents the power connections (R Y B ).
We can run the motor in star connections as well as Delta connections depending on what is written on the name plate of the motor, name plate of the motor is the specification sheet and if we understand we are through.
This is a very simple name plate sufficient to give some idea. It shows that if winding is connected in Delta then 3 Phase 400 VAC to be given, but if winding is connected in Star then 690 Volts to be given
[Can you analyse the circuit as given in the windings above to understand this 690 from 400 ?]
Then it gives the full rated current as 29/17 Amps, it talks of Kw and RPM as 1430 U/Min.
[Q. Now what is U/Min or RPM ?]
It is basically the rotor rotations per minute. How do you calculate it ? You must have studied a simple formula that is RPM = 120 * f / p where f is the frequency of the power supply and p is number of poles. In our case f = 50 Hz and the number of pole is as per design of the motors. It could be 2P, 4P, 6P and 8 P etc. So for we can calculate as follows..
2P = 3000 RPM
4P = 1500 RPM
6P = 1000 RPM
8P = 750 RPM
Now the rotor will not move exactly at these values, it will move at less RPM due to slip and that is what creates the torque. So 1430 RPM of above name plate suggests that it is a 4 Pole motor.
[Now how do we calculate the Amp ?]
So, lets take a thumb rule for 415 VAC 3 Phase Motors
Rated Current = 1.5 * HP
This is the approximation and good enough for various selection as required for design of motor starters.
At the end of this you should know
[Stator, rotor, terminal connections, Star Connections, Delta Connections, RPM, Amp, Voltage, HP / Kw]
2. Gear Box
[Do we need speed reduction, if yes, why ?]
Gear Box is a mechanical device, generally used for speed reduction. They look as follows.
Gear Box Internal Cut Out, for a very simple gear box
So you can figure out that smaller wheel will rotate faster as compared to the bigger wheel depending on the number of teeth or diameter ration. So if motor is connected to smaller wheel, and load is connected to bigger wheel then you will get speed reduction.
[Q. In the Gear Box picture you see one shaft of smaller diameter then the other shaft. Why ?]
3. Gear Motor
The Motor is same, only thing is Gear Box comes factory fitted with the motor.
The advantage here is that, you can ask for your required rating and required RPM at the final output shaft from the manufacturer itself.
There are various types of Gear Boxes, helical Gear Box, Worm Gear Box, Multi stage Gear Box, Planetary Gear Box, Multi output Gear Box, Cast Iron Body Gear Box, Aluminium Frame Gear Box. Please google and know about them. The idea is to get different RPM at output shaft as per application / load requirement.
[ Q. Do you know the relationship between Power, Torque and RPM ? Are you aware of P=2pi*N*T ?]
Example - 1. Motor Connected with Load with Pulleys and V - Belt.
3. AC Brake Motor
The normal AC Motor shaft will have a brake, there is a manual release lever also as shown above. This brake is Electrically actuated, and separate connection is provided for the same. If you do not want Brake Motor then you can install Brake on the motor shaft also, as normally done in case of Elevator and Crane vertical motion motors.
[Q. What will happen to elevator or crane of Brake is not applied ?]
4. Motor Starters for 3 Phase 415 VAC Class AC Motor
This will cover many many items as listed below and will help you understand the Electrical Aspect of starting an AC Motor.
[DOL Starter, Star Delta Starter, AC Drive, Softstarter, MCB, MCCB, Contactor, OverLoad Relay, Push Buttons, Indication Lamps, Wire Size Selection, Contactor Selection, OverLoadrelay Selection, MCB Selection]
Starter is a circuit basically used to start a motor. The idea is to give 3 Phase 415 VAC supply (3 wires) to connect to the motor terminals. As soon as power supply is made on to these terminals, the motor would start rotating. So how do we give supply to these terminals.
Simplest of all is DOL starter, it requires an MCB (isolator) and a contactor and few Buttons. So we learn about these components..
MCBs
Generally used for protection and isolation. They are available from 2 Amps to 63 Amps, in 1P, 2P, 3P and 4P combinations. For 3 Phase AC motor we need 3P MCB of suitable rating. As discussed above a 3 Phase AC motor approximately takes 1.5 * Motor HP as the current, so if we have to start at 10 HP motor, we would need an MCB which can carry 1.5 * 10 = 15 Amps current, so we choose an MCB of around 25 Amps.
 |
| MCBs of 1P, 2P, 3P and 4P types |
for example, in a 3P MCB (Bottom right), you see three terminals below and 3 terminals above, you can connect power to bottom 3 Terminals (R Y B) and when MCB is on the power comes on to upper 3 terminals. In case of any short circuit or fault MCB trips and power is isolated from the upper terminals.
 |
| MCB Trip Mechanism |
[Q. What are the standard MCB current ratings ? Where do we use 1P or 2P or 4P MCBs ?]
Contactors
Above are the typical images of a contactor. It has a power circuit and a control circuit, Power Circuit is for main motor Ampere / current flow, for example above contactor is of 110 Amps (See A110), Control part is required to actuate the contactor (A1 and A2 terminals as shown above).
