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# Tag Info

39

I have to start with some terminology -- sorry if it's esoteric, but this will bring things into line with how folks talk about this subject. When you turn a permanent-magnet DC machine*, the armature generates a voltage internally. This is called the "EMF"** of the armature, or the "back EMF" if the machine is running as a motor. This EMF is always ...

31

It is true that it's only the volume and the power fed to the winding that matters for magnetic field, in electromagnets and motors. Therefore, you could have a single turn winding. Unfortunately, a single turn would (generally) require a very high current and a very low voltage. This is true on the scales we tend to work at, and the values that physical ...

15

This diode is to surpress any back-EMF caused when the motor is switched off. In general, when one has an inductive load such as a motor, or an electromagnet's solenoid, when you switch it on, there will be an initial drop in current, as some of the current will act to form a magnetic field around the coil. Inversely, when switching off, this magnetic field ...

15

Recently, I bought the H-Bridge VNH7070BAS from ST because it would drive up to 15A It will not drive anything like this level of current for anything more than a few micro seconds before the automatic current limit circuit operated. The internal transistors together contribute circa 0.1 ohm impedance in the current path and, at (say) 10 amps continuous, ...

15

No. You don't match rotations per second to PWM frequency. It needs to be much higher. You want it high enough so the motor runs smoothly (motor inertia smooths out motion and motor inductance helps smooth out current), but not so high the switching losses in your electronics is excessive. Often at least 8-10kHz, but you might want >20kHz if audible noise is ...

14

You want the motor inductance to result in reasonably low ripple in current during the PWM cycle. Here is one drive maker's rule of thumb: $f_{PWM} \ge \frac {0.6V_{SUPPLY} }{L_{MOTOR}\cdot I_{NOMINAL}}$ This formula results in quite a bit of ripple, around 40% peak at the limit and D=50%, so a bit higher frequency might be desirable, especially if the ...

13

Sounds like you have low frequency conducted EMI. An X-capacitor straight over the motor would be the first order of business, but I've included the steps I would have taken down the line (litterally). simulate this circuit – Schematic created using CircuitLab Couldn't find a symbol for you motor, nor lines to draw a correct CM choke. More luck with ...

13

simulate this circuit – Schematic created using CircuitLab Figure 1. Two connection methods. The windings on your motor can take 220 V between their terminals. On a 220 V 3-phase supply you connect as shown in Figure 1b. On a 380 V 3-phase supply you connect as shown in Figure 1a. Note that in each case the voltage across each winding is 220 V ...

13

Air has a much higher reluctance (the magnetic equivalent of resistance) than the magnetic materials used in the motor. The smaller the air gap is, the lower that reluctance, and thus the higher the magnetic flux (which is the magnetic analog of current), allowing the motor to work more efficiently and at a higher power. Smaller air gaps also minimize ...

12

This component is a undervoltage protection device. When the voltage is high enough the device will close a make contact so current can flow. When the voltage is to low the contact will open or stay open. This is a over voltage-relay, but imagine it with the smaller than(<) character. Link to image

11

This is a 3-phase permanent magnet (PM) servomotor. Induction motors do not have permanent magnets, therefore it is a synchronous motor. If any two phase connections between the motor and controller are swapped, the motor will reverse. Since the controller can reverse the motor electronically, it may make no difference how the motor is wired during ...

11

A normal DC motor has 3 poles instead of just 2. This solves a couple of problems: the commutator doesn’t short out as it crosses from one pole to the other. the energized poles are always phased with the field magnets such that they never get in a place where they’re ‘stuck’. This Quora link has an animated illustration that shows the idea: https://www....

10

Why can't I just have one big wire or threaded wire on a motor? No problem with this - check out the rotor on most induction motors: There is no insulation on the aluminium (squirrel) cage and it is, in effect, one shorted turn. What is it about having multiple coils that enables the magnetic field? A magnetic field is produced by current AND turns ...

9

Motor is free on a table and shaft is not connected to anything. It's most likely an imbalance in the motor plus a mechanical resonance in the "mounting". Try clamping it down to a nice solidly built table or bench, and repeat your test. Chances are that the problem will go away, or at least be minimized and shifted in frequency.

8

The reason you need it to be insulated is to ensure that the current goes around each loop when you coil it. If it weren't it could just go "straight". You can have one big wire indeed, but you would need more current to produce the same results. That is what the number of turns N actually gives in all the magnetic field formulas. It actually lets you have ...

8

The spikes seem to have a few common heights that are roughly related by factors of 2, which strongly suggests that they are noise-induced single-bit errors in the binary data. One good way to address this is to take the standard deviation of all the data, and then simply throw away any samples that are more than, say, 2σ from the mean. Another ...

7

The motor is an INDUCTIVE LOAD. Due to Faraday's Law of Induction stating that a time varying/changing current creates a magnetic field with a magnitude directly proportional to the change in the current through the conductor over time and ( as much symmetry exists in physics) a changing magnetic field creates an electric field (a voltage difference) ...

7

This answer was given prior to the op changing the question. Originally, the question referred to the motor as being a squirrel cage type. Subsequently, after several comments, the op changed it to a brushless motor. You just can’t get the staff any more! When you stall a 3 phase motor it becomes a transformer and, because the rotor is the secondary AND is ...

7

Turn to the 'drawings' tab on the data sheet you linked to. You'll see that the boss around the output shaft is threaded M5.5x0.5. Drill a 5mm diameter hole in your plate, tap it M5.5, and screw the motor in. You've done the right thing by choosing a motor with a data sheet (many don't). But you have to read it for it to work.

6

One easy way would be to put a toroid or ferrite on the cable, they increase the inductance on the cable for high frequency signals and prevent conducted emissions. I've had success with a radio and blocking emissions from a PC with the mains cable from the radio wrapped around a ferrite toroid. You can also get clamp on ferrites almost everywhere. This ...

6

Brushless DC motors (BLDC) or permanent-magnet synchronous motors (PMSM) are pretty much the same thing and are the best to use as generators. They generate AC, so they require a rectifier on the output. There is no way to regulate the generated voltage except to regulate the speed. You will need a charge controller or other electronic power converter to ...

6

The number of turns is irrelevant. All changing the number of turns does, assuming you also change the wire diameter so that the resulting winding fills the space available, is to change the impedance of the winding, the voltage/current ratio, not the efficiency. Consider the space filled with two identical windings, running at the same current, voltage, ...

6

If you take the ratio of line voltage to the phase voltage for a 3 phase system supply you get $\sqrt3$ = 1.732. Now 380 divided by 220 is 1.727 (about 0.3% off from perfect) so this informs that if the windings are Y connected, each winding receives 220 volts from a 380 volt 3 phase supply. Try this picture of a 120 volts/208 volt set-up: -

6

Edit: Following the suggestion of Chris Stratton and lucasgbc, I tried to remove an inaccuracy I did due to a too quick reading of the datasheet and to emphasize the reasons of the results the asker found in his measure of the maximum output current. I hope I succeeded in providing a nicer answer. The maximum output current stated customarily in datasheets ...

6

There are many 12v fuel pumps that are designed to run submerged in gasoline, like this one for example https://www.amazon.com/WALBRO-255LPH-PRESSURE-GSS342-Authentic/dp/B0098MC3GU You should look into pumps specifically designed to be used with fuels; there may be ones specifically rated for kerosene.

6

Difficult to say without seeing the switches and wiring, but I would suspect a bad connection or wiring fault somewhere. You do not say if it has always been like this or if the fault has developed recently. One of the wire terminals on the switches may be lose or corroded, or maybe at the lamp, motor or distribution board. I would very much doubt that the ...

5

It's an single phase BLDC (Brush less dc) motor. the circuit is an hall effect sensor to detect the rotor position. Some thing similar to this follow this link for more information on control and working of an single phase BLDC motor

5

You can also tear down the machine and make sure the commutator and brushes are tip-top. The source of the EMI may not be the machine itself, but defects or wear in the machine.

5

It is actually quite simple. It the nameplate states Δ/Y 220/380 this means that this motor is designed and can be connected in delta, if the line voltage is 220 volts. If the line voltage is 380 V then the motor can be connected in star. This comes from the fact, that the the max allowed voltage per motor winding is 220 volts. In either case the the ...

5

Most of what is written about induction motors is about 3-phase motors. In a 3-phase motor, the magnetic fields rotate smoothly in one direction. Single-phase motors accomplish the same thing with two windings that, in effect, are energized as a two-phase system. There are several schemes to accomplish that.

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