Chapter 25, Problem 94A

To determine

To Explain:The way, common tools such as the electric drills, circular saw are constructed using the universal motors and how this type of motor can operate on the AC or DC current.

Explanation of Solution

Introduction:

The universal motor is one of a type of electric motor. It can operate on boththe AC and DC power. The universal motor makes use of electromagnet as it is a stator and can create the magnetic field.

The universal motor is called as an AC series of motor. The construction of the universal motor

is same as the DC series motor but it has some modification done on it in order to operate the universal motor on AC.

It can operate effectively on the AC because the current in both of the fields including the coil and the polarity will be reversed by the armature at the same time with the supply of current.

The motor works on either the AC or DC supply. As soon as the motor is given a DC supply it starts working on the DC series motor.

When a conductor which is carrying a current is placed in the magnetic field a mechanical force is applied on the conductor. Due to the mechanical force, the rotor starts its rotation.Its direction is given by Fleming’s Left hand rule.

The AC motor produces unidirectional torque. The reason is that the windings of the armature are in series and they are in same phase. Due to this, the polarity of the AC changes from the time to time and the direction of the current and the armature are reversed simultaneously.

Conclusion:

Hence, a series of DC current has the use of both the components an armature and a coil. When it is operated on an AC current there is change in the polarity at both the fields at the same time. The polarity of the magnetic field does not change so the direction of the rotation is constant.