This motor combines a power on activated type clutch and brake with an induction motor. It is ideal for high-frequency starting and stopping. Suitable for applications where the motor is operated starting, stopping and reversing repeatedly and the motor is operated at synchronous speed regardless of load torque.
What is meant by constant speed motor?
The American Institute of Electrical Engineers has defined the constant-speed motor as one the speed of which is either constant or does not materially vary; such motors are the synchronous motor, the induction motor with small slip, and the direct-current shunt motor.
Is DC series motor a constant speed motor?
The DC shunt motors are self-regulatory i.e. there is no much change in both speed and flux across them. So, in a shunt DC motor speed remains constant, while in DC series motor speed is variable.
Are AC motors constant speed?
The speed of an AC induction motor is a function of the AC frequency, the number of poles in the motor, and the load on the motor. Under no-load conditions, the speed is quite constant. Under load, the speed will vary since the motor torque comes from the lag in the phase current.
What is the difference between a constant speed motor and a synchronous motor?
Even on loading, the speed is always constant but the torque angle (between stator and rotor magnetic poles) may vary. If load increased beyond certain limit, the rotor may fall out of synchronism and motor to haul. A synchronous motor runs at synchronous speed only because it is meant to run like that .
What is constant speed?
Definition: When the speed of an object remains the same – it does not increase or decrease – we say it is moving at a constant speed.
Which motor is used for constant speed application?
Both ac and dc motors are suitable for constant speed applications. DC motors provide full torque at zero speed and have a large installed base. AC motors are also a good choice because they have a high power factor and require little maintenance.
Why is the DC motor preferred over AC motor?
Because DC motors have higher starting torque compared to AC motors, they are preferred for applications like electrical traction. They are considered ideal for dealing with heavy loads for starting conditions in machines such as locomotives and cranes.
Which motor has the poorest speed control?
Which of the following DC motor has the poorest speed control? Explanation: DC series motor at no load condition gives infinite speed ideally. Practically it will damage all the armature circuit. Thus, as the load is reduced speed of the motor will go on increasing rapidly.
Which motor has highest no load speed?
Explanation: At no load, armature current tends to zero, flux φ tends to zero, where speed is inversely proportional to the flux, speed will tend to infinity. Thus, no load speed of DC series motor is highest.
What happens when the AC motor is turned on?
As the coils are energized, the magnetic field they produce between them induces an electric current in the rotor. This current produces its own magnetic field that tries to oppose the thing that caused it (the magnetic field from the outer coils). The interaction between the two fields causes the rotor to turn.
How do you control the speed of an AC motor?
Although they are constant speed devices, AC motor speeds can vary if the frequency, input voltage, or the windings that make the motor rotate are changed. A common and efficient means of changing a motor’s speed is to vary the frequency by use of an inverter as the power source.
What is the main disadvantage of synchronous motors?
Disadvantages or Demerits:
Synchronous motors requires dc excitation which must be supplied from external sources. Synchronous motors are inherently not self starting motors and needs some arrangement for its starting and synchronizing. The cost per kW output is generally higher than that of induction motors.
What are the advantages of synchronous motor?
The advantages of the synchronous motor are the ease with which the power factor can be controlled and the constant rotational speed of the machine, irrespective of the applied load. Synchronous motors, however, are generally more expensive and a d.c. supply is a necessary feature of the rotor excitation.