In Industry, Angle grinder plays a very important role. Many tasks such as cutting, grinding, polishing can be done easily with this small hand held comfortable machine.
Maximum industrial motors are Induction motors which run at a maximum speed of 2800 rpm at line voltage of 400V AC at 50Hz frequency. But these small hand held angle grinders can run from 5000 to 12000 rpm which is high, Very High.
In this post, We are going to explain the working & configuration of Angle Grinders.
ANGLE GRINDER
” Angle grinder is also known as ‘disc grinder’ or ‘hand grinder’. Through this hand held machine cutting, grinding & polishing can be done by just changing the working wheel. Angle Grinder is a type of series motor which can run on both AC & DC voltage. That’s why these motors are known as universal motors. “
This machine comes in different shapes, sizes & power ratings. There are different sizes of angle grinders are available such as 4″,4.5″,5″,6″& 7″(inches). This size is actually the diameter size of the wheel running on angle grinder.
An image of 4″ & 5″ angle grinders is shown below :
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PARTS OF ANGLE GRINDER
This Machine is actually an AC/DC powered series motor in which field winding works in series with armature winding. A same current flows through the both field winding & armature winding.
Next, We are going to discuss the parts of the machine one by one !
Field winding
Field winding is the stationary part places around the rotating armature rotor. In this winding; two coils with equal turns; are arranged opposite to each other & rotor rotates in between the field windings.
While running, This field winding produces a lot of heat due to the core loss(eddy current loss & hysteresis loss) that’s why field winding is fully insulated K7 laminated to minimize the loss.
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Armature (Simply can say a ROTOR)
It is the rotating part of the grinder Which also carries winding. The winding ends of armature are connected to the commutator.
(Commutator is round arrangement of copper strips on which armature wires are soldered.)
To hold the armature freely in the center, Bearings are installed on both the sides of armature. A special laminated insulation is layered up on the armature winding due to which full armature seems like a single solid piece.
A cooling fan & small gear is also fitted on top of the armature. That fitted small gear transmit the mechanical power to connected wheel.
Armature block is been shown through images below:
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Carbon brush
Since armature is rotating part. To pass the current through the armature & to connect field winding with armature winding, A carbon brush mechanism is adopted. In this carbon brush rub against the commutator strips.
Carbon brushes are made up of soft graphite material so that no harm happens to commutator. These carbon brushes are highly resistive & provides high resistance to the circuit. Over the time, due to continue running , these carbon brushes get rubbed Which need to be replaced.
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DPST Switch (Double pole single through Switch)
For ON- OFF, DPST switch is provided. This switch contains 2 poles, Both the poles; phase & neutral; are been operated through a single switch.
Grinder works when DPST switch is pressed. For continuous operation, A switch lock is also provided to lock the DPST switch.
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Gear head assembly
A gear assembly is connected on the head of angle grinder at which working wheel is mounted.
A small gear which is mounted on the armature shaft which transmit the rotating power to gear head assembly.
For changing the working wheel, A lock is provided on gear head assembly which is used to dismantle the working wheel easily.
Gear head assembly is shown below:
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WORKING PRINCIPLE OF ANGLE GRINDER
“Whenever a current carrying conductor get placed in magnetic field; torque get produced. That is working principle behind the working of angle grinder.”
Armature which is placed in between the field windings. When power supply is get applied, Both the windings; field winding & armature winding becomes electromagnet. In this arrangement armature behave as current carrying conductor placed in a magnetic field of field winding. Which results torque get produced on armature.
This torque rotates the grinder in a fixed direction. The direction of rotation always remains the same because same current flows through the both field & armature windings. Even in case of supply reversal, rotation remains the same because change of supply occurs in both the windings simultaneously.
WIRING DIAGRAM OF ANGLE GRINDER
Phase & neutral both passes through DPST (Double pole single through – A Single switch Which can operate the both phase & neutral ).
Both the wires are connected to each end of both the field windings & another terminal of field winding connected to carbon brushes. At last, Armature is placed between the carbon brushes.
This whole wiring constitute a series connection. First current passes through one of the field winding, then through one of the carbon brush, motor’s armature, then through another carbon brush & at last through the another field winding.
Clearly shown & explained in a next image.
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Applications of angle grinder
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Cutting metal rods and pipes
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Grinding weld joints
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Polishing metal surfaces
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Cutting tiles and concrete
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Removing rust and paint
Advantages of angle grinder
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Easy to use
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Portable tool
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High-speed operation
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Multiple uses with different discs
Limitations
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Produces sparks and noise
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Risk of injury if not handled properly
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Not suitable for accurate cutting
Safety precautions
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Wear safety goggles and gloves
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Use the correct disc
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Do not remove the safety guard
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Hold the grinder with both hands
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Switch OFF power before changing disc
FREQUENTLY ASKED QUESTIONS (FAQ)
Q1. Which motor is used in an angle grinder?
A. A universal motor is commonly used in angle grinders.
Q2. What is the RPM of an angle grinder?
A. The RPM usually ranges from 6,000 to 12,000.
Q3. Can an angle grinder cut concrete?
A. Yes, with a diamond cutting disc, it can cut concrete.
SUMMARY OF ANGLE GRINDER
- Angle grinders are compact powerful high speed machines with running speed ranges from 5000rpm to 12000rpm.
- Angle grinder is basically a AC series motor that are also known as universal motor.
- The rotor(armature) rotates in between the field windings.
- Rotor of this machine also contains winding which is known as ‘Armature‘.
- To pass the power through the rotor, carbon brush & commutator method is adopted. Carbon brushes have been pressed against the commutator with the help springs.
- After long run, Carbon brushes get deteriorated which further needs a replacement.
Hope you like the post! If you have any doubt or suggestion please do comments. Your comments are valuable to us.
Can an Angle Grinder Cut Concrete?
Technically No !It is not safe & easy to use angle grinder on concrete.For concrete cutting there are concrete cutters available which are safe & easily to use.
Can you change the direction of turn by exchanging the carbon brush end with polarity end on both the two field windings ?
No, Direction of rotation will not change by changing the carbon brush ends.
Motor rating is 0.6 KW. The motor which is used in this; is series induction motor. Which is specially designed for these type of applications.