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because N=(120*f)/P where N= speed in rpm f= frequency in Hz P= no. of poles as the relations shows above it is cleare that speed of machine inversly proportional to no. of poles.. so as the poles increses, speed of the machine decreses
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Why is motor current draw lower at full speed?
Because full speed is unloaded. As you load the motor, speed decreases, and slip increases, with an accompanying increase in current.
As a motor armature turns faster and faster net current in the motor windings decreases or increases or remains unchanged?
as a motor armature speed increases,the net current in the motor windings decreases due to MAGNETIC DRAG. which is a common phenomenon in the ac machines.
How speed of a squirrel cage induction motor can be varied?
There are two ways of changing the speed of AC motors,by altering the frequency or the number of poles in the motor. An increase in frequency of the supply voltage to the motor will cause it's speed to increase while reducing the frequency will causes the motor speed to drop. This is the method exploited by Variable Speed/Frequency Drive. The second method of changing the number of motor's stator poles is the difficult. The manufacture must design the motor such that the number of the motor's pole in operation can be increased or reduced. Increasing the number of poles increases the stator flux density which decreases the speed. Decreasing the number of poles does the opposite. This method is typically found in two speed motors and it's rarely used compared to VSDs.
If you increase or decrease the frequency what effect on electrical machin?
If you're talking about an electric motor, increasing the frequency will increase the speed of rotation of the motor, and decreasing the frequency will decrease the speed of rotation of the motor. The other way of controlling a motor is to control the current; increasing the current increases speed, decreasing current decreases speed.
Does the motor speed double when the armature voltage is doubled?
Yes, because as the armature voltage increases, the speed also increases so they are proportional.
What is the effect of increasing number of poles on the speed of an induction motor?
As the number of poles (P) increases, the speed of an induction motor (N) decreases. As seen by the formula: N=(120*f)/P
Why is motor current draw lower at full speed?
Because full speed is unloaded. As you load the motor, speed decreases, and slip increases, with an accompanying increase in current.
As a motor armature turns faster and faster net current in the motor windings decreases or increases or remains unchanged?
as a motor armature speed increases,the net current in the motor windings decreases due to MAGNETIC DRAG. which is a common phenomenon in the ac machines.
How speed of a squirrel cage induction motor can be varied?
There are two ways of changing the speed of AC motors,by altering the frequency or the number of poles in the motor. An increase in frequency of the supply voltage to the motor will cause it's speed to increase while reducing the frequency will causes the motor speed to drop. This is the method exploited by Variable Speed/Frequency Drive. The second method of changing the number of motor's stator poles is the difficult. The manufacture must design the motor such that the number of the motor's pole in operation can be increased or reduced. Increasing the number of poles increases the stator flux density which decreases the speed. Decreasing the number of poles does the opposite. This method is typically found in two speed motors and it's rarely used compared to VSDs.
What increases when a wave period decreases.?
When a wave period decreases, speed increases.
How does speed affect Power?
Speed is directly related to power. As speed increases, power also increases. And as speed decreases, power also decreases.
Why induction motor current increase when load increase?
The slip is proportional to the load torque in an induction motor. This can also be seen as a reduction in speed causing extra current to be induced in the rotor to supply the increased torque.
Why speed increases if its acceleration decreases?
stamina
Why should a series motor always start with a load?
In any DC motor the speed depends inversely on the flux. 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. If u start the motor without load the speed will increase. as speed increases the back emf increases. this decreases the current through the series winding and hence flux decreases and the speed further increases. Theoretically speaking the speed becomes infinite. But practically the motor will accelerate to very high speed , which will damage the motor. But if you start the motor with the load, you are actually reducing the starting speed hence the motor runs safely. Since series motors has this property it is used in trains to pull high load.
What happens to the speed of a wave if the frequency decreases and the waveleNgth increases?
the wave decreases.
If the waves speed stays the same what decreases as the frequency increases?
The wavelength decreases.
Single phase motor speed is determined by the?
Motor's number of poles.
