Maintopik5

E4102- DC MOTOR CONTROL
FADZILAH BINTI HASHIM
E4102- DC MOTOR CONTROLLED
(KAWALAN MOTOR AT)
TOPIK 5 – ELECTRIC BRAKING
LECTURER : FADZILAH BT HASHIM
012-5469607

REGENERATIVE DYNAMIC
PLUGGING
ELECTRIC
BRAKING

5.0 Introduction
Slow or stop a motor and load pacuannya as important as the beginning of
many applications such as cranes and traction(tarikan) on a slope to prevent
excessive speed.
Method based on friction braking, electromechanical response, eddy currents
and so forth.
It does not depend on the motor, but sometimes electric braking (electrical
braking) is better, especially in terms of economy and the absence of wear on
the brakes (brake wear).
DC motors are widely used as a means of holding or braking.

5.0 Introduction
DC motors are widely used as a means of holding or braking.
One reason for this is a good braking characteristics and the ability to change
(transition) the motor current from the generator mode (mod penjana) and vice
versa.
During the period of braking, the motor berkendali sbg generator and energy
(potential energy) the kinetic (kinetik) or gravity (Gravitational) degenerative
(dissipated) to the resistance (plugging) or returned to the supply (regenerative
braking).
Electromechanical braking is a process to stop the motor. Braking can be done
to stop the rotation of the motor armature.
For larger motors there is inertia load (armature rotates) on the motor.
Therefore it can not be dismissed so quickly.

There are three types of braking
method;
Dynamic braking.
Plugging braking.
Regeneration braking.

5.1 Dynamic braking
Braking is more popular.
It is a way to stop the rotation of the motor armature where armature
disconnected from the supply source but connected to the external resistance.
When the external resistance is connected, the current,Ia will change
direction, the torque will happen with the fight against the direction of rotation.
The opposite direction of this torque causes the motor to stop. In this way also
the armature current can be limited during the braking process.
This method can be briefly described as figure 5.1

Figure 5.1 The block diagram of the dynamic braking method
Referring to figure 5.1 before the braking output voltage dynamics are as follows;
Eo = Va - IaRa
After the dynamic braking???
5.1 Dynamic braking

Selepas pembrekan dinamik.
Power during the initial braking is ;
5.1 Dynamic braking

Referring to figure 5.2 the armature is separated from the supply
and a braking resistor, Rb directly connected merintanginya. In
this way the motor acts as a generator, driven by the stored kinetic
energy to generate power to the Rb .
5.1 Dynamic braking

This is a simple method of bringing the motor close to stop conditions.
Braking time is dependent on the system inertia, load torque and motor rating.
When the braking circuit is connected to left field to supply the input. One danger
is that if supply fails, the braking will also fail.
If the field is left connected across the armature, resulting in braking torque is the
same but start falling with the the high rate of slope which propotional to speed,
then the problem arises once the speed falls below the critical imperative of self
(self-excitation).
For the series motor, it is necessary to reverse the continued braking whether the
field winding or armature winding to produce the emf in the armature.
Rb values must be (Rb + Ra + RSE) is less than the critical resistance to the
speed at which braking is made.
5.1 Dynamic braking

Example calculation of dynamic braking:
1. A DC series motor with the supply 240V using a chopper with a
duty cycle 75% motor speed in the eddy current 15A and
armature resistance 0.15Ω is 1000rpm. If the motor stopped by
dynamic braking of the external resistance 0.35Ω and moment of
inertia 95kgm2
. Calculate:
- Initial braking power
- Mechanical time constant
-Time the motor to reach 25% initial speed .

5.2 Plugging braking
In this method of supply to the armature will be disconnected from the
supply source and reconnected to the opposite polarity.
Change of polarity will cause the torque generated in opposite
directions, and against the direction of rotation.
These changes cause the motor to stop immediately. This method is
shown in Figure 5.3.
Faster than the dynamics of 2Tm.

Power when Initial braking, P = (Va + Eo)Ia.
Time to stop the motor Tb = 2Tm.

Referring to figure 5.4 this braking method involves the exchange and at the same
connection on the field winding (field) or the armature coil (armature) while the motor
is berkendali. A powerful braking torque is obtained by setting the same voltage
supply with armature while the connections is inverted.

Armature voltage is used (Ea + V) is in ≈ 2V, thus the limiting braking resistor (also
can resistor starters) should be placed on the circuit. Kinetic energy caused by the
movement of the system is removed (dissipated) to the armature and braking
resistance
Whichever method is electrical braking will become less effective as speed is
reduced due to a reduction in braking torque of the supply shall be disconnected
at a speed close to 0 (except to change the motor rotation direction) by means of
a current relay or router speed and wear a mechanical or hydraulic brakes for
cause the motor is stationary. High starting currents and mechanical stress could
limit the application of the method of plugging, especially to a small motor.

Tm = time for the motor speed decreased by 50% of actual speed.
J - moment of inertia at the motor shaft rotation (kg/m2
)
W1 - the actual speed when you start braking (rpm)
P1 = the actual power received by the braking resistance of the armature

Contoh pengiraan Pembrekan plugging:
1 A series of DC motor with a 240V supply using the chopper 75% duty cycle in the
15A eddy current motor and 0.15Ω armature resistance when speed is 1000rpm. If
the motor stopped by braking plugging using a series resistance of 2.23Ω. Calculate;
- Current and power during the initial braking.
- Time to stop the motor.

5.3 Regenerative Braking(Pembrekan penjanaan semula)
In this process of braking the motor will function as a generator. Motor is fed
energy from the supply. Chopper is used to rise and reduce the voltage. Referring
to figure 5.5 :

When the chopper Ch1 work, the machine will function as a motor and the chopper
Ch2 off, the energy stored in the motor will be discharged through the diode D1,
thereby reducing current flow. When the chopper CH2 work, the motor voltage to be
generated. Opposite currents will flow through the chopper and the energy stored in
the motor. When the chopper CH2 off, energy will be released in the form of current
through the diode D2 to supply.

Referring to figure 5.4 chopper voltage;
Vch = (I – D)Vs (where D is the duty
cycle )
Power generated
Pg =
IaVs(I - D)
= IaVch
The voltage generated when the motor acts as generator
Eo = Kv.IaW
Eo = Vch + IaRm
= (I – D)Vs + IaRm

THANK YOU……THANK YOU……

Maintopik5

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