Today we will discuss about electromagnetic clutch. In my
previous posts we have discussed about types of clutch. We know that according
to the engaging effect, clutch has two types. The first one is positive
displacement clutch and the other one is friction clutch. Every clutch requires
a holding force which takes care of proper engaging and disengaging clutch. This
force is sometimes obtained by spring stored energy and sometimes by other
source of energy. An electromagnetic clutch
is also a friction clutch which uses electromagnetic force to engage and
disengage the clutch.
After reading this paragraph, some questions arises in our mind.
1. What is electromagnetic force?
2. How a clutch uses this force to engage and disengage clutch?
3. How a practical electromagnetic clutch works?
You can find answer of those questions in this
article.
What is Electromagnetic force?
It is a fundamental force associated with electric and
magnetic field. In simple words, two particles attracted towards each other
due to electric charge or magnetism is called electromagnetic force. It is a
stronger than gravity but weaker than nuclear force. This force comes into
action when two electric charges or magnetic particles comes into contact. Any
magnet attracts iron pieces towards it due to electromagnetic force.
Electromagnetic Clutch:
Principle:
Before discussing about electromagnetic clutch first you
should know about basic fundamentals of clutch. Clutch is a device which engage or
disengage two shafts called driving shaft or engine shaft and driven shaft or
gear box shaft. A simple basic clutch consist two pressure plates, one is
connected with engine shaft and other one with gearbox. The pressure force
is applied by the spring arrangement which forced these plates towards each
other when the clutch pedal is not pressed. There is a friction plate between
both of these pressure plates. When the engine shaft rotates, it makes rotate the
gear shaft due to friction force between them. When the driver press the clutch
pedal, both pressure plate loose contact with each other and clutch is in
disengage position.
This is basic of any clutch. All friction clutches work on
same principle. An electromagnetic clutch is also a friction clutch but it
uses magnetic force in place of spring force to engage and disengage the
clutch. It also consist two clutch plates (Rotor and Hub). One of them is connected with the
electric circuit. When the electricity passes through this plate, it converts it
into electromagnet which attract the other plate towards it. There is also
a friction plate between them. The magnetic field apply force to connect both these plates and friction plate transmit torque between them. Thus this clutch is combination
of both electromagnetic effect and mechanical clutch. Now we will discuss construction and working of this clutch.
Construction:
This clutch consists following parts.
Rotor:
Rotor is a major part of this clutch witch is connected
directly to the driving shaft or engine shaft. It continuously rotate along with
the driving shaft.
Winding or Coil:
Winding coil is situated behind the rotor and remains in
stationary position during clutch working. It is shown in figure. A high
voltage DC supply is connected with this winding which transfer a high voltage
current into this winding and convert it into electromagnet.
Armature:
Armature is situated at front of the rotor. It is connected
to the hub or pressure plated with the help or rivet or bolted joint.
Hub:
Hub or pressure plate is bolted with the gear shaft or
driven shaft and rotates with it. It is situated after the armature.
Friction Plate:
Friction plate is inserted between armature and rotor
according to the requirement.
Supply unit:
Supply unit consist clutch switch, battery, wire etc.
Working:
The electromagnetic clutch working can be summarized into
following points.
- In the initial condition the clutch is in disengage position. There is an air gap between rotor and hub.
- First the engine starts which makes rotate the rotor connected with the engine shaft.
- A DC battery supplies DC current into the clutch winding.
- This high voltage DC current converts this winding into an electromagnet which attract armature towards it.
- This armature force friction plate towards the rotor and make rotate the hub.
- Thus the hub rotate and the rotor transmit 100 percent torque during engage position.
- When the clutch switch / pedal is pressed, the battery stops the supply in winding which remove the electromagnetic force, thus the clutch is in disengage position.
Advantages:
- No linkage is required to operate the clutch. So it can be installed any remote location.
- It can be used to achieve automatic transmission.
- Easy to operate.
- Less wear and tear at contact point.
Disadvantages:
- This clutch operating temperature is limited by the temperature rating of the insulating material.
- High initial Cost.
This is all about electromagnetic
clutch principle, working advantages and disadvantages along with its diagram.
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