BEE 1961,
Test venue for each section as below:
E11: Industrial electronic lab (F8)
E12: Industrial electronic lab (F8)
E13: Machine control lab (F13)
Reminder: Test schedule as below
Date: 15-April-2011(Friday)
Time: 2.30 pm
Wednesday, April 13, 2011
Industrial application of Star Delta starter
Star Delta is categorize as a reduce voltage method
Reduced voltage methods are intended to reduce the impact of motor starting current on the power system by controlling the voltage that the motor sees at the terminals.
Common applications which require controlling the starting current or torque can be found in many industries including material handling, HVAC, mining, and waste water treatment where the main applications are fans, pumps, conveyors, and compressors.
This circuit allows the motor starter to initially connect the leads in a star connection for starting, and then reconnect them in the delta configuration for running
This method is usually employed on motors rated below 600V. Motors rated 2.3kV and higher are usually not suitable for Star-Delta starting. In term of power, it is suitable for motor rated above 7.5 Hp (5.5 kW)
Fans can be either directly connected to the motor or belted. The fans that are belted usually require torque control during starting to eliminate or reduce excessive belt wear as a result of slippage during across the line starting.
Pumps have low starting torque profiles. The initial torque and acceleration torque can be critical in some pumping applications and is usually determined by the design of the pump. Some pumps such as those with long shafts connecting the motor to the pump, may be damaged if the starting toque is too high.
some types of compressors need low torque to accelerate to full speed. Reciprocation compressors require high starting torque especially when starting under load. Other types such as centrifugal and axial vane type require low starting torque because of the design characteristics.
The need to limit the inrush current may be due to government mandates, power company restrictions, distribution system limitations, or operation in areas that are adjacent to or within a residential area may need to limit current during starting to eliminate voltage drops that cause light flicker.
A good example of this is on pumps for hydraulic elevators in an apartment complex. These pumps have low starting torque requirements, so limiting current during starting minimizes any line sags that would have occurred if the pump was started direct on line.
Reduced voltage methods are intended to reduce the impact of motor starting current on the power system by controlling the voltage that the motor sees at the terminals.
Common applications which require controlling the starting current or torque can be found in many industries including material handling, HVAC, mining, and waste water treatment where the main applications are fans, pumps, conveyors, and compressors.
This circuit allows the motor starter to initially connect the leads in a star connection for starting, and then reconnect them in the delta configuration for running
This method is usually employed on motors rated below 600V. Motors rated 2.3kV and higher are usually not suitable for Star-Delta starting. In term of power, it is suitable for motor rated above 7.5 Hp (5.5 kW)
Fans can be either directly connected to the motor or belted. The fans that are belted usually require torque control during starting to eliminate or reduce excessive belt wear as a result of slippage during across the line starting.
Pumps have low starting torque profiles. The initial torque and acceleration torque can be critical in some pumping applications and is usually determined by the design of the pump. Some pumps such as those with long shafts connecting the motor to the pump, may be damaged if the starting toque is too high.
some types of compressors need low torque to accelerate to full speed. Reciprocation compressors require high starting torque especially when starting under load. Other types such as centrifugal and axial vane type require low starting torque because of the design characteristics.
The need to limit the inrush current may be due to government mandates, power company restrictions, distribution system limitations, or operation in areas that are adjacent to or within a residential area may need to limit current during starting to eliminate voltage drops that cause light flicker.
A good example of this is on pumps for hydraulic elevators in an apartment complex. These pumps have low starting torque requirements, so limiting current during starting minimizes any line sags that would have occurred if the pump was started direct on line.
Thursday, March 3, 2011
Leakage current detector (RCCB)
The Fault current overloads and short circuits
can be detected by circuit breakers like MCB’s
MCCB’s & HRC Fuses etc. But, Circuit
breakers don’t detect leakage currents, which
are dangerous for humans and livestock and if
not detected can lead to fire hazards. We need
a solution that detects such leakages currents
and disconnects the circuits from the power
supply. Here comes the solution in the form of
RCCB (Residual Current Circuit Breaker) also
known as ELCB (Earth Leakage Circuit
Breaker) which provides protection against
direct and indirect contact of personnel or
livestock and against probable fires.
RCCB works on the principle that in an electrical circuit the incoming current is the same as out
going current as shown in the Diagram. RCCB incorporates a core balance transformer having
primary and secondary windings and a sensitive relay for instantaneous detection of fault signal.
The primary winding lies in series with the supply mains and load. Secondary winding is
Connected to a very sensitive relay. In a faultless situation, the magnetizing effects of the current
carrying conductors cancel each other out. There is no residual magnetic field that could Induce a
voltage in the secondary. During flow of leakage current in the circuit an imbalance is created in
the circuit which gives Rise to leakage flux in the core. This leakage flux generates an electrical
signal that is sensed by the relay and it trips the Mechanism thereby disconnecting the supply.
can be detected by circuit breakers like MCB’s
MCCB’s & HRC Fuses etc. But, Circuit
breakers don’t detect leakage currents, which
are dangerous for humans and livestock and if
not detected can lead to fire hazards. We need
a solution that detects such leakages currents
and disconnects the circuits from the power
supply. Here comes the solution in the form of
RCCB (Residual Current Circuit Breaker) also
known as ELCB (Earth Leakage Circuit
Breaker) which provides protection against
direct and indirect contact of personnel or
livestock and against probable fires.
RCCB works on the principle that in an electrical circuit the incoming current is the same as out
going current as shown in the Diagram. RCCB incorporates a core balance transformer having
primary and secondary windings and a sensitive relay for instantaneous detection of fault signal.
The primary winding lies in series with the supply mains and load. Secondary winding is
Connected to a very sensitive relay. In a faultless situation, the magnetizing effects of the current
carrying conductors cancel each other out. There is no residual magnetic field that could Induce a
voltage in the secondary. During flow of leakage current in the circuit an imbalance is created in
the circuit which gives Rise to leakage flux in the core. This leakage flux generates an electrical
signal that is sensed by the relay and it trips the Mechanism thereby disconnecting the supply.
Wednesday, March 2, 2011
BEE 1961 Motor Control: Venue for test
Venue for test 1 as below:
1) Section E11BB & E12BB: F7 (Lab Analogue)
2) Section E13BB: F8 (Lab Electronic Industry)
Please be punctual.
Good luck
note:
1) study on PPE
2) motor name plate
2) Current transformer
3) etc
1) Section E11BB & E12BB: F7 (Lab Analogue)
2) Section E13BB: F8 (Lab Electronic Industry)
Please be punctual.
Good luck
note:
1) study on PPE
2) motor name plate
2) Current transformer
3) etc
Sunday, February 27, 2011
BEE 1961 Motor Control _Test 1
Test will be held on:
Date: 4-March-2011 (Friday)
Time: 2.30 pm
Venue: will be announced later
Which will cover:
1) Safety
2) Chapter 1: Motor Control ystem
3) Chapter 2: Devices & Component
Date: 4-March-2011 (Friday)
Time: 2.30 pm
Venue: will be announced later
Which will cover:
1) Safety
2) Chapter 1: Motor Control ystem
3) Chapter 2: Devices & Component
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