Page 274 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Precaution
i The agitator should be stopped during the drain period, because if it were to continue operating
without water in the tub, the required force on the agitator to rotate the clothes in the absence of
water would be many times more causing motor to overload.
ii The bottom cable should be protected from the damage by the rats by using a rust proof
welded mesh.
The drive motor: The most popular type of motor used in a washing machine is a single phase 240 volts 50 Hz.
capacitor start squirrel cage induction motor. These motors may range from 1/3 to 1/2 HP rating. These motors
are normally protected from overload and overheating conditions by means of a bimetallic overload relay or a
thermal switch. The motor is located in such a way that water leakages do not fall on to these motors.
Locating the machine: The machine should be so located that soft water is freely available, and outlet or water
drain arrangement is also easily available. The supply board should have the rated 3 pin socket arrangement with
proper earth brought to the 3 pin plug point. The flooring should be in level such that the machine rests properly
to avoid unnecessary loading on the machine drum and vibrations.

Induction Heater

Objectives: At the end of this lesson you shall be able to:
• explain induction heater
• explain construction, advantages and disadvantages of induction heater.

An induction heater uses an electromagnetic field to heat food. When the heater is turned on, an electric current
passes through a coil of metal, creating a magnetic field. This magnetic field then penetrates the metal of a
cooking pan, inducing a current in the pan. The current then dissipates energy in the form of heat, cooking the
food in the pan. (Fig 1)
What is induction?

Electromagnetic induction, which is often referred to simply as induction, signifies the production of an electric
current across an electric conductor, caused by a changing magnetic field. Electricity and magnetism are not two
disjointed things; they are two entities originating from the same underlying phenomenon - electromagnetism.
Due to this, a change in a magnetic field leads to the generation of electric current. Similarly, a change in the
electric field across a conductor produces a magnetic field. The latter is the working principle behind induction
heater, which is pretty much all you need to know to understand the working of induction cooktops.

Fig 1 Fig 2
Fig 1

Induction heater
Inside view of an induction heater (Fig 2)

261
CITS : Power - Electrician & Wireman - Lesson 101-103