What Happens If the Series Field of a Cumulative Compound DC Motor Is Short-circuited?

Total MMF created in Cumulative Compound motor is due to series field MMF and Shunt Field MMF.MMF = MMF(sh)MMF(se)As the series field is short circuited, current through series field is zero and MMF due to series field becomes zero.Hence total MMF in motor becomes less than previous case, which results in total decrease in the Flux created. As Electromagnetic Torque (Te) is proportional to armature current and total Flux, the Te by motor will be reduced.Edit:Also, as flux decreases, the new operating speed will be more than its operating speed.What happens if the series field of a cumulative compound DC motor is short-circuited?.

1. how to program a dc motor using PIC18F452 to move 30 degree evrey 2 hour until 180 degree and then return?

if u can switch this to a synchronous AC motor i can probably help you

2. In the brushed DC motor, what is the term brushed means ?

Each segment is soldered to a loop of copper wire. A circuit is thus formed via the I/P -through the 'brushes',- to the commutator, then to the motor windings, thus creating an ELECTRO-MAGNETIC field in the motor windings. This reacts with the motor's surrounding permanent (static) magnets causing rotation of the armature. Should a bad circuit be formed by a badly worn brush, sparking will occur causing failure of the inevitable motor. failure.

3. Why can't I vary the speed of a dc motor with only a potentiometer?

You CAN vary the speed with a simple potentiometer. BUT you must use a pot of a resistance value appropriate for the circuit. In your example you use a power source with a low impedance, and your motor has a low impedance. But you are using a pot with such a high impedance that it wo not let enough current through to turn the motor unless it is essentially at the top of its range.Note, however, that if you DO use an appropriately low impedance pot, you will be burning up most of your power in the pot which will not only kill your battery quickly, but may even be dangerous to the pot, causing overheating and premature failure.Furthermore, controlling the speed of something like a DC motor by varying the voltage (even in an efficient way) is a poor technique. It limits the motor to low torque at lower speeds because of limited power. That is why it is more common to see PWM (Pulse-Width Modulation) used to control motors (and lights/LEDs as well). PWM allows motors to have more torque at low speeds. And it is also much more efficient (less wasteful of power) because the controlling element (typically a transistor) is either full-on, or full-off. So very little of the power is wasted as heat in the control element. This is the common method used with microcontrollers like Arduino, et. al.

4. where can I find a speed controller for a DC motor?

A general pace controller with no trouble needs the PWM supply, a switching device and something to manipulate the motor again emf. Mostly character bipolar transistors are not rated at a lot present, and vigor is misplaced within the switching, because the beta may just most effective be 10 or so. The IGBT is more suitable and available in larger sizes. So are energy MOSFETS, so it depends what you select. It could be crucial to have two or three contraptions in parallel for warmth causes. All three contraptions mentioned can with no trouble perform this venture. Bear in mind the peak current in the course of motor starting may be so much greater, depending how you function the process. To get regulated speed there desires to be a feedback manage and a tachometer. This works very similar to the governor on a diesel engine. You desire a three time period controller (PID controller) for best operation. There can also be inner and outer control loops to control current and acceleration too, so it makes sense to purchase a pace controller. Should you best want to differ the pace manually just like the throttle on a petroleum engine, the circuit would be as simple as a 555 timer (or 2 of them) to generate adjustable PWM, with proper drivers for the gate circuits which can be high capacitance. The switching speed handiest needs to be a few hundred Hz, but must be chosen so it would not rationale mechanical resonances in windings and many others. Be conscious that the motor can get overheated if it has a fan and runs at low velocity high torque. There are pace controllers for RC electrical model planes that switch these form of currents or more, utilising a variable width pulse to control the velocity. The pulse varies from 1 to 2ms width for velocity control, and needs to be repeated every 20ms or so. Maybe this fits your want

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Maximum Value of Back Emf in Dc Motor?
The back EMF is proportional to speed. As the load increases, the speed will decrease. That will cause the back EMF to decrease. Note that there is a voltage drop across the armature resistance. That voltage drop plus the back EMF is equal to the supply voltage1. DC motor speed is too low while interfacing with L293D motor driver and ATmega8Here's what the L293D spec says: -In red I've extrapolated what this means for a 6V battery supply. So, in a H bridge you can not really expect to put more than 3 or 4 volts onto your motor from a 6V supply. The device is not modern and it is not geared up for driving 6V motors from a 6V supply. Also note the current drive capability of the device is 0.6A which is poor for driving any decent mechanical load2. If carbon is non-metal, then how do carbon brushes in a DC motor transmit electric current?Actually carbon brushes of DC motor are made from a weak conductor of electricity, called graphite. It is an allotrope of carbon. This material has a smooth planar lattice arrangement and has a lot of "valence" electrons or free electrons in the lattice. These electrons can move when an electric potential is applied to the sides of a graphite plate.3. How can I obtain the torque of DC motor knowing that I have the voltage signal?If it has a nameplate, find the part as listed by a distributor. Look over the specs supplied by the distributor4. What is the difference between 24v-20 Amps DC motor and 230v -2 amps DC motor?When you connect load to the generator, the motor needs more Torque to drive the generator shaft.... For a DC motor, the torque generated is directly proportional to the current taken & Inversely proportional to speed ----------->Thats why the second motor is able to drive the the generator.5. DC Motor's don't stop immediatelyWhile I totally agree with the other answers on the issue of using a non-blocking timer, I would like to add another factor about motor braking from a purely "electrical" point of view.......To "brake" a running DC motor, you need to short the two terminals. This will generate a back current in the coil which will reverse the magnetic field and stop the motor much faster than by just cutting off power to the terminals. This is not possible to implement using a Bi-polar H bridge motor driver like L293D. You need to use a MOSFET type H-bridge6. Can you use an AC switch with a DC motor?Hi, . . . Usually NO.. . For low voltages 12V DC should be OK, even 24V might be OK, if it is a big switch.. . But depends on the switch design and how it physically works. . . But generally NO7. Pull away voltage (energy) from a DC motor driver board when it does regenerative brakingThe obvious solution is a clamp that conducts if the voltage tries to go above 50 V. Something like this:-simulate this circuit - Schematic created using CircuitLabYou can not do that because the voltage at that point is a mains frequency sine wave going from 0 V to 50 V. To feed power back into the transformer you would have to convert the DC voltage into AC with the correct voltage and phase.8. Does operating a DC motor at low PWM freq (500 Hz and below) deteriorate the motor performance?there is no rule that applies to all motors, but in general if the frequency is high enough the inductance of it becomes more relevant and it tends to heat up more easily. An advantage is that most humans cannot hear those frequencies so it would make less sound that you can hear at least. Increased heat can damage winding and other parts easily so you can have that in mind. At low frequencies, the ripple of the current is more pronounced, this makes the motor less efficient in general, but I doubt it causes any issues due to stress or anything else, it just runs less efficiently if the frequency is too low9. Current limiter for small 12V DC motorSorry it is now past 1 AM here and I am getting tired. I just wanted to give you a heads-up what the idea was. The bridge rectifier makes sure that the current through the circuit always goes the same way, no matter which way the motor turns. simulate this circuit - Schematic created using CircuitLab
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