Adding a Switch for Direction Reversal in 12v DC Motor W/ PWM Controller System

Figure 1. Modifications required.You can reverse the motor with a double-pole, double-throw (DPDT) switch.Be careful with this. Reversing the motor while at speed will cause high currents to flow as the momentum of the motor must be overcome to reverse it

1. How diodes protect H-bridge DC motor driver?

To supplement Anindo's fine answer, specifically, the voltage across the inductor (i.e., in this case the motor) is $$ L fracdidt $$Thus, when current is cut off suddenly (exactly what an h-bridge wants to do, especially when controlled as a PWM), $fracdidt$ gets extremely large and there is an associated very large spike in voltage. The diodes protect the MOSFETs from these spikes.

2. Can a DC motor be of specification 320Watts, 3A, 24 V?

Sure, they can print anything they want on the sticker. As you noticed, $24:mathrm V cdot 3:mathrm A = 72:mathrm W$. To get 320W in any sense (mechanical, electrical, or thermal power) would require more voltage, more current, or both, or a violation of the law of conservation of energy. One then wonders, how do they get 320W?My guess (since the sticker is too brief to say): "320W" is the maximum theoretical mechanical power this motor could produce.A DC motor driven by a fixed voltage has a maximum no-load speed, and a maximum torque which is developed at zero speed. That maximum no-load speed is limited by the battery voltage (here, 24V), and the maximum torque is limited by the stall current, which is not specified but which is probably (a lot) more than 3A. You can get a rough idea by measuring the winding resistance with an ohmmeter, then calculating what the current would be into that resistance at 24V with Ohm's law. Sometimes you have to jiggle the rotor to get the commutator to line up.A linear function then describes the torque vs. speed relationship for a given motor, at a given voltage. From Understanding D.C. Motor Characteristics:Mechanical power is the product of torque and speed, and thus, the motor develops maximal mechanical power at the midpoint of this line, where the motor is running at half its maximum speed and delivering half its maximum torque."320W" likely refers to this maximum theoretical mechanical power. Of course, the motor will overheat if you actually run it under those conditions for very long. Briefly however, it will be fine, as long as you do not generate more heat than would be generated by 3A continuously, or generate so much torque as to damage the motor mechanically

3. i want to make a dc motor which should run on 10v.?

I would use thirteen.5v at 1.Zero amp. I might location a resistor in sequence in line between the source voltage and the three fans wired in parallel. You are going to need the series resistor to drop 1.5 volts throughout it. The present flowing via the resistor should be (a hundred thirty ma one hundred thirty ma 130 ma) or 390 ma (0. 390 amps). For that reason, 1. 5 v / 0. 390 amps = 3. 85 ohms (use 4. Zero ohms) rated at I^2 x R (0. 390 amps ^2 x 4. 0 ohms) = 0. 600 watts (use 1. 5 watts). The in line resistor must then be 4. 0 ohms at 1. 5 watts. The adapter should force the three parallel lovers just best

4. Strongest DC motor I can find in the 1-1.5 pound range?

Power is speed times torque, so you need either high speed or high torque. If you use a high speed motor, then you need a high speed gear box, which wo not be cheap. Anyway, the most powerful motor will be one that uses Neo permanent magnets, but its not real cheap. For this small size a DC machine will probably be the best choice

5. PID control at small PWM values for a DC motor

You have backlash in the gear train which is like electrical hysteresis. That is causing "hunting". You can minimize the backlash by preloading as in anti-backlash gears. You can adopt a simpler control scheme such as P (perhaps with some control deadband) or PD. The integral term, if present, will integrate any remaining error until motion occurs (unless the I term has deliberate or accidental deadband itself - say due to low ADC resolution).You might want to read this paper by Tim Wescott. Tim does a lot of work with precision electromechanical systems used in military and similar applications.

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Shunt DC Motor Controller Improvement
Shunt DC motor controller improvementSo this looks as if the circuit controls armature current?It controls armature voltage.would it be better if the winding current was controlled?Controlling armature current with an outer voltage or speed control loop would be better, but more complex.By "winding current" I suspect you mean field winding current as apposed to armature winding current. Controlling the field winding current would make the minimum operating speed about equivalent to the present maximum speed. Reducing the field current will increase the speed and reduce the torque capability. I doubt very much that is what you want.The above seem to be the only actual questions asked. The question seems to imply that you wish to improve the control scheme because the motor " runs slightly erratically." You have not actually described what aspect of motor performance is undesirable.Speed decrease with increased load is normal for a simple armature voltage control. Random speed variation with a steady load could be due to line voltage variation, other power quality issues, motor brush problems or a loose connection. Failure to start relably would like be a brush problem— — — — — —Can you use an AC switch with a DC motor?Just follow the ratings of the switch. Typically, the DC voltage rating is less than the AC voltage rating. Current ratings are normally the same— — — — — —What is an interpole in a DC motor?Thanks for A2A.Purpose of Interpole in DC MachineFor understanding the role of Interpoles, we need to understand the effect of armature reaction in the DC Machine. The effect of armature mmf on the main field flux is to distort the main field flux and to reduce the net main field flux. The figure below, shows the effect of armature mmf on the main field flux. It is quite clear from the above figure that the flux at the location of Carbon Brush i.e. A, B and A are not zero and therefore an EMF will be induced in the coils undergoing commutation and will lead to the sparking. As we know that for better commutation, the coils short circuited by the brushes should have zero EMF induced in them. As the zero crossing of field flux is shifted due to armature reaction, the coils undergoing the commutation will have a net EMF induced in them. This induced EMF in the short circuited coil will delay the reversal of current in the short circuited coils and will result into poor commutation and sparking at the carbon brushes.The question arises how to resolve this issue?If we see the figure above, we observe that there is a net shift of zero crossing of net flux in the air gap by an angle Ɵ in the direction of rotation for Generator and opposite to the direction of rotation for Motor. So the cheap and easy solution shall be to shift the Carbon Brush at Zero Crossing of the air gap flux.Thus carbon Brush need to be shifted by an angle Ɵ from Geometrical Neutral Axis (GNA) in the direction of rotation for Generator and opposite to the direction of rotation for Motor.But this method of shifting the Carbon brush has a big disadvantage. What is that?As the Armature Reaction depends on the current flowing through the armature winding which in turn depends on the load current. Therefore as the loading of the DC Machine varies the angle Ɵ will also vary and therefore we need to continuously shift the Carbon Brushes. So we need to find a smart way.Again, looking back to the figure, if it could be possible to make the resultant or net air gap flux zero at GNA, then there would not have been any detrimental effect of armature reaction on commutation. Also, the existing flux at the GNA (at point C) is due to North Pole so we could use a South Pole (opposite of the pole which produced the imbalance at C) at C so that the net flux at C becomes Zero. Similarly at C' we can use a North Pole to make net flux Zero there. Okay, this will work fine but how t change the magnitude field strength of this newly installed poles at C and C'? Hmmmm. .We can use a winding on the newly installed poles at C and C' and connect that winding in series with armature winding so that the strength of field due to newly installed poles at C and C' varies proportionally will the loading of machine. Yes, this will work fine.So we can conclude our solution as,We will use Poles same as that of Main Poles ahead of GNA or Carbon Brush for Generator at the location of GNA or Carbon Brush and Poles same as Main Pole that of behind the GNA or carbon Brush for Motor at the location of GNA or Carbon Brush and will use winding on them and connect them in series with the armature winding as shown in figure below.The Poles used in our smart solution is called the Interpole. Interpoles are narrow poles placed at the GNA and fitted to the Yoke and also known as Commutating Poles or Compoles. For generator, the polarity of Interpoles must be same as that of main Pole ahead of it in the direction of rotation. For Motor, the polarity of Interpole must be same as that of Main Pole behind it. So I expect that you understand the purpose of Interpoles as you only designed it. But there is one more interesting role of Interpole.Interpole do not only nullify the effect of armature reaction but in addition, produces some extra mmf in the interpolar zone. This extra mmf in the interpolar zone induces rotational EMF in the short circuited coil undergoing commutation in such a direction to oppose the reactance voltage in the coil. Thus the resultant the resultant voltage in the short circuited coil becomes zero and the commutation is spark less.What is an interpole in a DC motor?
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