Skip to main content

Dynamic Breaking


Application – Motors, especially ones attached with fly wheel, de-energized upon pressing the stop button will still rotate due to inertial energy stored in the rotors. This motor condition is quite dangerous in some application. Many person loss their fingers after they stop motor thinking that there is no longer any effect to the machine which the motor drives. See figure below (A) and (B).

Theory of Application


Consider Figure below (A). Rotor R due to the rotating north and south poles at poles A, B, C and D. The Rotating north and south poles A, B, C, and D rotates because of AC voltage is remove from lines L1 and L2, the rotating poles at poles stops rotating because of inertia, the rotor R remains rotating. The rotor may rotate few seconds or even minutes depending upon the load it carries.


 (A) Rotor R will still rotate even if the AC voltage at lines L1 and L2 is removed.



Motor Control circuits- Dynamic Braking

(B) Rotor R come to stop immediately if the AC voltage at lines L1 and L2 is substituted by a DC voltage.



Motor Control circuits- Dynamic Braking

If after removing the AC voltage at lines L1 and L2 is immediately substituted by DC voltage, a steady (none  rotating) north and south poles stays at poles A, B, C, and D. See figure above (B). These steady north and south poles at poles A, B, C, and D will lock the rotor R and will cause it to stop immediately.


Diode

A Diode is a device that allows  the flow of current in one direction but blocks the current in the opposite direction. See Figure below (b) and (c).  


(a) An actual and schematic diagram of a diode.

(b) A half wave rectifier where the diode is conducting

(c) A half wave rectifier where the diode is not conducting.


Motor Control circuits- Dynamic Braking

(d) A full wave bridge rectifier using 4 diodes.


Motor Control circuits- Dynamic Braking

Full Wave Bridge Rectifier

The full wave rectifier shown in figure above (d) converts the AC voltage at input L1 and L2 to DC voltage at the output load L.


Operation of full wave rectifier

During the positive half cycle, current flows in line L1, D1 down to load L, D3, and line L2. This give a positive current (downward Direction) in the load L. During the negative half cycle, current flows from D2 down to load L, D4, and line L1.This also give a positive current (downward direction) in the load L. Notice since the direction at the load L1 is always downward, the Ac input at lines L1 and L2 is converted to pulsating Dc output in the load L

Circuit Operation of a Dynamic Braking


Figures below (A) and (B) illustrate the power and control circuit of a “Dynamic Braking”. Note the contactor C has 2 normally closed auxiliary contacts C (11-12) and C (21-22).

Pressing the start push button will energize contactor C. Contact C (13-14) will closed to maintain the control circuit. Contacts C (1-2,3-4,5-6) will close to energize motor M to lines L1, L2, and L3. Contacts C (11-12) and C (21-22) will open to ensure that no DC current from the bridge rectifier can enter the motor windings at terminals T2 and T3 while the motor is operating under an AC source.

(A) Control circuit of the Dynamic Braking.





Pressing the stop push button will de-energize contactor C. Contactor C (14-15) will open and release the control circuit from maintained condition. Contact C (1-2,3-4,5-6) will open to de-energize the motor M. Contacts C (11-12) and C (21-23) will return to close position. At This condition the motor may still run some several rounds.

(B) Power circuit of the Dynamic Braking.


Using the dynamic brake (DB) push button for stopping the motor instead of the ordinary push button. If the DB push button is pressed instead of the stop push button, contactor C will also de-energized. Contact C (13-14) will open. Also contact C (1-2,3-4,5-6) will open to disconnect the motors for lines L1, L2 and L3. Contact (11-12) and C (21-23) will return to close position. If the DB push button is pressed further to short its contacts DB (3-4), the dynamic brake contactor DB is energized. Contact DB (11-12) will open to ensure the contactor C will not be energized. Contacts DB (1-2) and DB (3-4) will close to permit the DC current from the bridge rectifier B to enter the motor windings at terminals T2 and T3. This will bring about the sudden stopping of motor M.
 

Comments

Popular posts from this blog

Build a 3000W Stereo Power Amplifier Circuit Diagram

How to Build a 3000W Stereo Power Amplifier Circuit Diagram? Lets start first we define 3000wstereo power amplifier circuit diagram this circuit has a power output of up to 1500W RMS power amplifier circuit is often used to power sound systems spelunker for outdor. In the final image can be seen a series of power amplifiers using 10 sets of power transistors for the ending. This power amplifier circuit using a transistor amplifier from the front, signal splitter, driver and power amplifier. Current consumption required is quite large power amplifier that is 15-20 A 1500W power amplifier circuits for this. Supply voltage needed by the power of this amplifier is the optimal working order symmetrical 130VDC (130VDC-130VDC ground). 1500W amplifier circuit below is a picture series of mono, stereo if you want to make it necessary to make two copies of the circuit. For more details can be viewed directly image the following 1500W power amplifier circuit. The series of High Power Amplifier 15...

Build a Key Operated Gate Locking System Circuit

This simple key-operated gate locking system allows only those persons who know the preset code to open the gate. The code is to be entered from the keypad within the preset time to operate the motor fitted in the gate. If anyone trying to open the gate presses a wrong key in the keypad, the system is disabled and, at the same time, sounds an alarm to alert you of an unauthorized entry. Figs 1 and 2 show the block and circuit diagrams of the key-operated code locking system, respectively. Connect points A, B, C, D, E, F and ground of the circuit to the respective points of the keypad. Keys S7, S16, S14 and S3 are used here for code entry, and the remaining keys are used for disabling the system. It is very important to press the keys in that order to form the code. To start the motor of the gate, press switches S7, S16, S14 and S3 sequentially. If the keys are pressed in a different order from the preset order, the system will lock automatically and the motor will not start. Fig. 1: Bl...

A basic Arduino Solar PV Monitor

I have just recently had solar pv installed, mainly to future proof my energy costs, I do not expect it to be like drilling for oil in my back garden, however the return looks to be encouraging. The install gives you another single unit meter, from this you will see the total amount the panels produce, but that is about it. I wanted to know how much the production was as it was happening, I discovered the light blinks on the front of the meter will flash 1000 times for each kWh of electricity which passes through. The rate of the flashing of the LED tells you how much power is currently passing through the meter. [ ]