Motors Flashcards
What is the rule for the developed force for the motors?
F=(l*ß)*i
What is the eqn for the induced torque in the motors?
Tind=(i*L*ß)*r
Describe the theory of operation of the DC motor?
- A DC supply is applied to the field winding(stator) this inuces a magnetic field
- A DC supply is applied to the rotor through the comutator and the brushes causing a DC current to pass in the rotor circuit
- Therfore a torque will be produced on the armature winding
What is the Eqn for the developed torque?
Td=Ka*Ø*IA
Ka=(2P/2a)*Z/2π
Z is number of conductors
Td=K*If*IA
Draw the power flow diagram of the DC motor and label it and state the EQNS?
What are the types of DC motors?
Self excited:
- DC shunt
- DC series
- DC compound
Seperatly excited motors
Draw the separatly excited DC motor?
Draw the DC shunt motor?
Draw the speed torque charcatristics of separtely and shunt DC motors and derive the eqn of the slope?
What are the applications of the DC shunt motors?
- It is used when the speed needs to be constant from no load to full load
- belt driven applications
- Drills
- Machine tools
- Spinning and weaving machines
Draw the series DC motor?
Draw the torque speed charactristics of series DC motors and derive the slope?
What are the applications of series DC motors?
- Elevators
- Electric cars
Draw the DC short compund motor?
Draw the DC long compund motor?
What are the advantages and disadvantages of armature voltage speed control?
Advantages:
- Wide range of speeds
- No resistance losses
Disadvantages:
- Expensive
- Only used for values below base speeds
What are the advantages and disadvantages of field current speed control?
Increasing field resistance leads to decrease in field current and decrease in the flux and so the speed increases
Advanatges:
- Cheap
- Low power loss
Disadvantages:
- Only for speeds below base speed
What are the advantages and disadvantages of armarure resistance speed control?
Avantages:
Disadvantages:
- High losses
- Poor regulation
- low effciency
Not commenly used
