An induction motor develops torque by inducing current to the rotor, which is proportional to the differential speed of the rotor and the rotating magnetic field in the stator. For NEMA design B motors the differential speed (called slip) is between 1% and 2% at full load.
What is torque in an induction motor?
Torque is the turning force through a radius – with the units Nm in the SI-system and the units lb ft in the imperial system. The torque developed by an asynchronous induction motor varies when the motor accelerates from zero to maximum operating speed.
How do you increase the torque of an electric motor?
To increase the torque … that a bit harder. All you can do, electrically (as you can do it mechanically via gears), is to reduce the source impedance to maximise the current that can be delivered for a given stator impedance. Rewind it with more turns of thinner wire.
How the starting torque can be increased in squirrel cage motors?
Abstract. There were many attempts to design the rotor bar shape to increase the starting torque in squirrel cage induction motor, and it is well known that deep slot of rotor bar increases the starting torque. However, this deep slot increases the leakage flux so that it hurts the running efficiencies.
Why does the speed of an induction motor fall as the load torque is increased?
The speed of the motor is directly proportional to the EMF induces across the rotor terminal. This EMF causes flow of current in the rotor bars which causes torque over the rotor shaft . … As the load torque increases the electromagnetic torque decreases and vice versa..
What is motor torque formula?
As you see this equation torque is the product of the force and the distance between the force and the center of rotation. For example, if you want to hold the force acting on the end of pulley, T = F x r.
What is maximum torque in induction motor?
The developed torque is maximum when the rotor resistance per phase is equal to the rotor reactance per phase under running conditions. By putting the value of sX20 = R2 in the equation (1) we get the equation for maximum torque.
Does more torque mean faster acceleration?
Basically, the faster the crankshaft spins with the same amount of force, the more power an engine will make. A car with more hp than torque will always be quicker since this gives a car acceleration and speed. … Higher torque doesn’t mean one vehicle will necessarily be faster than another, though.
Can you increase torque without increasing horsepower?
To answer your question, yes, torque can be increased in a car without changing the horsepower through gearing. Torque = A measurable a twisting force. It’s measured in an instance with no regard to time. Horsepower = (RPM x Torque) / 5252.
How do you check motor torque?
A relatively simple method to estimate torque on the output shaft of an electrical motor is to measure its electrical power input via an electrical power meter. The meter calculates the power input by measuring the current and voltage in the line driving the motor.
How do you increase starting torque?
There are three ways to improve the starting torque of induction Motor
- Internal Rotor Resistance. The across the line starting torque at low speed can be increased by increasing the rotor resistance. …
- External Rotor Resistance. …
- Variable Voltage/Frequency.
What is low starting torque?
Abstract: Large single-phase motors (15-50 hp) have been developed. They are designed with very low inrush current and have low starting torque. … Breakdown torque and full-load (FL) performance are normal for single-phase motors.
Which type of motor has high starting torque?
DC Series motor has high starting torque. We can not start the Induction motor and Synchronous motors on load, but can not start the DC series motor without load. DC motor has high starting torque.In a series motor the same current flows through the armature and the field winding.
How does an induction motor start?
When the supply is connected to the stator of a three-phase induction motor, a rotating magnetic field is produced, and the rotor starts rotating and the induction motor starts. … At the time of starting, the motor slip is unity, and the starting current is very large.
Does plugging torque give zero speed?
Torque is developed in the opposite direction of the motor’s rotation, which produces a strong braking effect. … But when plugging is used to brake the motor, a zero-speed switch or plugging contactor is used to disconnect the motor from the supply when its speed reaches zero.
What happens to torque when you increase speed?
If you increase the torque you increase the speed UNLESS you increase the load. The important thing to remember is that with electric motors there is a back-EMF (a motor is a generator too) which increases with speed and that limits the effective voltage and thereby the current and thereby the torque.