Quick Answer: Which Motor Cannot Be Started On No Load?

Which motor has highest no load speed?

DC series motorExplanation: 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..

Which power is zero at no load?

An adapter is considered zero-power if its no-load power is measured to be less than 5mW when measured with an input voltage of 230Vac. Achieving less than 5mW of no-load power isn’t an easy task, as it involves compromises with other design targets.

Which motor is always started with load?

d.C. Series motorAt no load, it will rotate at dangerously high speed 2. It will fail to start 3.

Why starter is used in DC shunt motor?

Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor’s armature winding and restricts the current to an acceptable level.

What should be the no load current of an induction motor?

The I2R losses on the primary side is neglected as they vary with the square of the current as we know that the no load current is 20-30% of the full load current, As the motor is running at no load, the total input power is equal to the constant iron loss, friction and windage losses of the motor.

Why DC shunt motor is used in lathe?

The shunt motors are used where constant speed is required and starting conditions are not severe. The various applications of DC shunt motor are in Lathe Machines, Centrifugal Pumps, Fans, Blowers, Conveyors, Lifts, Weaving Machine, Spinning machines, etc.

Why is the DC motor preferred over AC motor?

DC motors have the advantage of: higher starting torque, quick starting and stopping, reversing, variable speeds with voltage input and they are easier and cheaper to control than AC. AC motor advantages include: lower power demand on start and minimal maintenance.

When load current is zero the zener current will be?

Answer. Answer: When load current is zero, the zener current will be 0.

Why DC shunt motor is started on no load?

For DC shunt motor the field resistance is high and armature resistance is low so the variation of flux is very less when rated voltage is applied to the motor and motor speed does not exceeds rated speed at no load. So we can start the DC shunt motor with no load.

Can you start a series motor without load if no why?

A series motor should never be started at no load. With no mechanical load on the series motor, the current is low, the counter-EMF produced by the field winding is weak, and so the armature must turn faster to produce sufficient counter-EMF to balance the supply voltage. The motor can be damaged by overspeed.

Why DC shunt motor is constant speed?

In a shunt motor, the shunt field current Ish is always a constant since the field winding is connected in parallel to the armature winding and the supply voltage. … If load change is not considered since a DC shunt motor has a constant flux φ and a constant supply voltage the speed of the motor remains constant.

What will happen when the DC motor is connected to AC supply then?

1. What will happen if DC shunt motor is connected across AC supply? Explanation: In case of parallel field connection, it won’t rotate at all and will start humming and will create vibrations, as a torque produced by positive and negative cycle will cancel out each other. DC motor will be heated up and it may burn.

What is back emf in dc motor?

When the armature of the DC motor rotates under the influence of driving torque, the armature of the conductors moves through a magnetic field inducing an emf in them. The induced emf is in the opposite direction to the applied voltage and is known as the back emf.

What is no load current?

While primary winding carries a small current I0 called no-load current which is 2 to 10% of the rated current. … This current is responsible for supplying the iron losses (hysteresis and eddy current losses) in the core and a very small amount of copper losses in the primary winding.

Why must the series motor be started with load?

Consider when starting a series motor the current flowing will be high, but the flux that the motor produces will be moderate since the series winding has less number of turns. … But if you start the motor with the load, you are actually reducing the starting speed hence the motor runs safely.

What are the applications of DC shunt motor?

The applications of shunt DC motor include the following.These motors are used wherever stable speed is required.This kind of DC motor can be used in Centrifugal Pumps, Lifts, Weaving Machine, Lathe Machines, Blowers, Fans, Conveyors, Spinning machines, etc.

What is no load speed of a motor?

The motor runs at the no-load speed when there is no load on the shaft. The maximum possible Torque is produced by the motor when the shaft is fully loaded and not allowed to move.

Which DC motor has got maximum self relieving property?

5. Which DC motor has got maximum self-relieving property? Explanation: DC series motor develops large starting torque initially and slow down with increase in load and so get automatically relived from heavy excessive load. Thus, DC series motor is called as self-reliving machine.

What is load current?

Load current in this context is simply the current thru the wire. As you say, a load consumes power. That power is delivered electrically, which means it is the product of voltage and current. The load current is just that current.

What is the principle of DC shunt motor?

A shunt DC motor has a feedback mechanism that controls its speed. As the armature rotates in a magnetic field, it induces electricity. This EMF is generated in a reverse direction, thus limiting the armature current. So the current through the armature is decreased and speed of the motor is self-regulated.

What will happen if DC motor is used without starter?

What will happen if DC motor is used without starter? Explanation: It would cause intolerably heavy sparking at the brushes which may destroy the commutator and brush-gear. Sudden development of large torque will cause mechanical shock to the shaft, reducing its life.