What are the 3 ways to increase the speed at which the electric motor changes ?

Explanation:

1.By increasing the applied voltage: Though this method is the easiest and cheapest, it is rarely used because a large change is supply voltage is required for relatively small change in speed. Also, large change is supply voltage disturbs the magnetic conditions of the motor.

2.By increasing the supply frequency: Increasing the supply frequency will increase the speed too. However, if the frequency is increase beyond the rated value, the developed torque falls while the speed rises.

3. Constant V/f control method: In this method, V/f ratio is kept constant when varying frequency for speed control. Keeping V/f ratio constant will also keep the stator flux constant and also keeping the torque approximately constant.

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation: