What is the effect of a reduced voltage on motor torque?
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What is the effect of a reduced voltage on motor torque?
When you have a voltage reduction, the current would rise to a new value, which may exceed the full-load rated amps. Low voltage can lead to overheating, shortened life, reduced starting ability, and reduced pull-up and pullout torque.
Why do we apply reduced voltage at the beginning of three phase induction motor?
The motor can also be started by applying a reduced voltage to the motor. The torque of the induction motor is proportional to the square of the applied voltage. Thus, greater torque is exerted by a motor when it is started on full voltage than when it is started on the reduced voltage.
How can we decrease the starting torque of an induction motor?
Adding more resistance will reduce the available torque, as the slip begins again to decrease. You can run Wound Rotor motors in a variable speed mode, if you can control the resistance, but that is generally very inefficient.
How does the supply voltage impact the torque of an induction motor?
∴ Maximum torque is directly proportional to supply voltage & maximum torque is inversely proportional to rotor reactance. Hence, the maximum torque is dependent on the supply voltage & reactance of the rotor and is independent of the rotor resistance. Hence maximum torque decreases by 20\%.
What is the effect of low voltage?
If the voltage is too low, the amperage increases, which may result in the components melting down or causing the appliance to malfunction. If the voltage is too high, this will cause appliances to run ‘too fast and too high’ which will shorten their service life. Leads, cables, cords and power lines are not at risk.
Why is it necessary to reduce the voltage to a motor when the frequency is reduced?
Why is it necessary to reduce the voltage to a motor when the frequency is reduced? A reduction in frequency causes a corresponding reduction of inductive reactance. The voltage must be decreased to prevent the motor from being damaged by excessive current.
What is the purpose of reduced voltage starting?
Reduced voltage starters are devices that start motors by reducing the power supplied at start-up. Reducing the power in turn reduces potentially damaging electrical and mechanical shocks on the system.
What is the main goal of using a reduced voltage starting with electric motors?
Reduced Voltage Starter is a device that starts motors with reduced power supplied at start-up. Reducing the power reduces potentially damaging electrical and mechanical shocks on the system. As the name implies, starters “start” motors. They can also stop, reverse, accelerate and protect them.
What are the methods of reduced voltage starting?
Types of Reduced Voltage Starters
- Primary Resistor.
- Auto Transformer.
- Part Winding.
- Wye Delta.
- Solid State.
How do you decrease starting current?
Some of the techniques used to reduce the starting current of a squirrel induction motor:
- Soft starting (voltage control)
- Variable Frequency Drives (Voltage and frequency control)
- Star/Delta Starting.
- Stator impedance and/or resistance starting.
- Autotransformer Starting.
Why do we have to reduce the motor voltage of an induction motor?
When motor operates at lower V/Hz than rated, the magnetic flux is reduced. Reduced flux reduces the torque capability and affects the motor ability to handle the load. Lower voltage while supply frequency is constant means lower V/Hz ratio and lower flux which affects the torque.
When the supply voltage to an induction motor is reduced by10\% the maximum torque will decrease by approximately?
When supply voltage reduces by 10\%, it becomes 0.9 times, therefore torque becomes 0.9^2 times i.e. 0.81 times i.e. 19\% less.