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- 17 May 2010
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Hi just doing a mock exam at the minute and have a few questions I cant answer. Can anyone telll us the answers
1 - All cable connections should be accessible for inspection exept cables
a- swimming pools
b- overhead lines
c- enclosed in non flammable material
d- sheathed in asbestos
2 - In a star connected motor the supply voltage is connected
a- to all 6 connections
b- across 2 windings in series
c- across 2 winding in paralell
d- across 3 windings in series
3 - In a delta connected motor
a- the supply is connected across each winding
b- the supply is connected to one end of each winding
c- the neutral point of the windings is at zero voltage
d- the neutral point of the windings are connected to the neutral of the supply
4 - Which of the following statments is correct
a- When a motor is single phasing the current and torque is low
b- In a star connected motor 1 winding will burn out if the motor is left single phasing
c- In a delta connected motor on winding will burn out and the other 2 windings over heat if the motor is left single phasing
d- Once a motor attains its rated speed single phasing will not cause any damage to the motor windings
5 - When a motor is operated through a star/delta starter
a- The starting current and torque is reduced
b- The starting torque and current is increased
c- The starting current is reduced and the tourque is incresed
d- The starting current is doubled and the starting torque is halved
6 - A single phase motor hums but the shaft does not rotate. This could be due to
a- One of the windings open circuit
b- The switched siezed in the on position
c- Both of the windings open circuit
d- No load being present on the motor
7 - When a motor is connected in delta and the resistance of each winding is 6R what reading will you get if you measure accross U1 and W1
a- 6R
b- 12R
c- 4R
d- 3R
1 - All cable connections should be accessible for inspection exept cables
a- swimming pools
b- overhead lines
c- enclosed in non flammable material
d- sheathed in asbestos
2 - In a star connected motor the supply voltage is connected
a- to all 6 connections
b- across 2 windings in series
c- across 2 winding in paralell
d- across 3 windings in series
3 - In a delta connected motor
a- the supply is connected across each winding
b- the supply is connected to one end of each winding
c- the neutral point of the windings is at zero voltage
d- the neutral point of the windings are connected to the neutral of the supply
4 - Which of the following statments is correct
a- When a motor is single phasing the current and torque is low
b- In a star connected motor 1 winding will burn out if the motor is left single phasing
c- In a delta connected motor on winding will burn out and the other 2 windings over heat if the motor is left single phasing
d- Once a motor attains its rated speed single phasing will not cause any damage to the motor windings
5 - When a motor is operated through a star/delta starter
a- The starting current and torque is reduced
b- The starting torque and current is increased
c- The starting current is reduced and the tourque is incresed
d- The starting current is doubled and the starting torque is halved
6 - A single phase motor hums but the shaft does not rotate. This could be due to
a- One of the windings open circuit
b- The switched siezed in the on position
c- Both of the windings open circuit
d- No load being present on the motor
7 - When a motor is connected in delta and the resistance of each winding is 6R what reading will you get if you measure accross U1 and W1
a- 6R
b- 12R
c- 4R
d- 3R