# Inductor dc motor

Although SPICE does not provide explicit models for electro-mechanical devices, like a DC motor, creating one is fairly straightforward. You just need to remember that most physical behaviors, whether mechanical or electrical, can be described by a set of equations. So for a desired mechanical behavior inertia, friction, etc. Then assign the mechanical parameters to the appropriate electrical component values and you're ready to simulate.

The motor converts the electrical armature current into a mechanical torque applied to the shaft. Components LJ and RB act as the motors mechanical inertia and friction. What is the back emf? It's the voltage generated across the motor's terminals as the windings move through the motor's magnetic field.

The back emf actually opposes the drive voltage and is proportional to the motor's velocity. Before we start up the motor, here's a recap of the circuit variables :. You can watch the back emf voltage grow as velocity increases by plotting V 3 in the original plot window. How much torque is required to achieve this speed?

Plot V 6 to see the Nm required. Look what happens when the 10V voltage is driven down to 0V. The motor slows down. But why should the motor current reverse, there's no voltage applied. Yes, that's true! But, with 0V applied to the motor, all of the back emf now appears across RM and LM causing the current and torque to reverse!

This reverse-torque action is referred to as dynamic braking. What about the angular position of the shaft? Open a new plot window and plot V 11 to see the shaft's position in rad. What do you expect it to look like? As the 10V is initially applied, the position should change slowly at first, then change increasingly faster until it hits full speed where the change in position is constant versus time.

When the 10V is removed, the change in position slows down until its stopped. You can simulate this by increasing the inertia LJ. How much longer does it take to reach full speed? Want to reach full speed quicker? Buy a motor with a higher torque constant. You should see a couple of nice effects: First, the motor gets to full speed in less time and second, the duration of the inrush current decreases!

You can sense current using any independent voltage source. Typically set to 0V, this source has no effect on the circuit. Applied Torque. Terminal Resistance.The Web This site. In a circuit which contains inductance Las well as resistance Rsuch as the one shown in Fig. The back EMF is produced because the changing current in the inductor causes a changing magnetic field around it and the changing magnetic field causes, in turn, an EMF to be induced back into the inductor.

Because the back EMF opposes the rapid change in current taking place in the inductor, the rate of change of current is reduced and what would be a vertical line on the graph Fig. The rate of change of current through the inductor is now less, so a smaller back EMF is produced. This allows the current to increase further. The relationship between the changing current and back EMF produces a curve which always follows a mathematical law to produce a particular shape of curve i.

Electronic Basics #12: Coils / Inductors (Part 1)

When the switch is opened, the current decays in a similar exponential manner towards zero. Looking at Fig. This is because a voltage is being applied to the circuit and little or no current is flowing because L is effectively for a very short time a very high resistance due to the back EMF effect caused by the rapidly changing expanding magnetic field around the inductor inducing a voltage a back EMF back into the inductor, which is in opposite polarity to the applied voltage from the supply, and so initially opposes the increase in current through the inductor.

Because of this opposition caused by the back EMF it appears initially that the inductor has a very high resistance. As current through L begins to build however, the rate of change of the magnetic field reduces, the oppostion due to the back EMF reduces and the apparent 'resistance' of the inductor falls to a low value the real resistance of the wire coil and the voltage V L decreases until a point is reached where the whole of the battery voltage is being developed across the resistor R; the voltage or potential difference pd across L is practically zero and energy is now stored in the magnetic field around the inductor.

When the current is switched off the magnetic field is now collapses instead of growing as it did at switch on. This collapsing magnetic field now returns its energy into the inductor coil and induces a voltage a back EMF into the inductor, but because the change in magnetic field strenth is in the opposite direction to the expanding field at switch on, the induced voltage is now in the opposite polarity, as shown in Fig.

The induced back EMF now opposes the reduction in current cause by switch off, slowing down the decay of current as can be seen in Fig. The rapid collapse of the magnetic field as the switch opens can cause very large voltage spikes, because the amount of voltage induced is dependent on the rate of change of the magenetic field. The high voltages produced can lead to arcing at the switch contacts, as the voltage jumps the gap between the contacts.

These large voltage spikes can also damage other components in a circuit, especially semiconductors, so care must be taken in the design of circuits containing inductors, or driving inductive loads, to prevent these spikes. In some circuits however, where high voltages are required, this effect can also be used to advantage, by applying a square wave to an inductor.

### Is a DC-motor an inductive load?

The very large voltage spikes produced can then be rectified by special high voltage diodes to produce DC voltages of thousands of volts. Hons All rights reserved. Revision Learn about Electronics - AC Theory. AC Theory Modules 2. Capacitors 3.The year has seen a great deal of success for the market sales of electric vehicles EV in the United States. The demand is expected to continue to rise in the coming years.

The success though should rightfully be credited to the motors of the EV. Behind the massive demand and great success of electric vehicles, future car owners are also looking into the performance of the motors. Two of the most innovative and best-performing motors to choose from are AC induction motor and DC brushless motor permanent magnet AC synchronous.

Both motors share the same purpose of elevating EVs and creating a healthier planet. Due to the exceptional wide speed range of the motors, EVs have acquired an impressive capability of running with just a single-speed gearbox.

The only thing that separates the motors from each other is the voltage usage. An AC motor is actually a three-phase motor that has a speed feature of running at volts. Car enthusiasts and experts deem this type of motor is adaptable.

Its regenerative feature can also work as a generator that brings back power to the battery of an EV. When it comes to road performance, electric vehicles with AC motors can get a better grip at rougher terrains and run more smoothly. It also has more acceleration. Even though AC induction motors are more expensive than DC motors, they are still popular to a wider market and automobile manufacturers because it is ideal for high-performance cars.

## Module 4.4

EVs with adaptable motors also last longer. In most cases, a DC motor will run between 96 to volts. The permanent magnet motor utilizes rare-earth elements into its magnets, which makes it unique. More car companies are also beginning to switch from induction motors to permanent magnet motors because it has a size and weight advantage that is more significant as automobiles are becoming relatively smaller.

They are also being used in almost all electric vehicles around the globe. One company that made a big jump in its motor usage is Tesla. A lot of people know that the famous California-based corporation applies an AC induction motor to all its model cars, but when Model 3 EV was showcased, it was discovered that they altered its motor. According to officials, the reason the reason for the change is that it does not need an additional electricity, unlike the AC motor.Wally Rippel is a long-time proponent of electric vehicles.

Wally has also worked for the Jet Propulsion Laboratory on electric vehicle battery research, among other projects. There are flat-heads, Hemis, straight, opposed, and V configurations. And on and on. One would have thought that, years ago, someone would have figured out which was best. That would have ended all the choices and thereafter only the one best engine type would be in production.

Not so. There is no one best engine type, rather there are different types of engines to suit personal requirements, such as price and performance.

## Select Your Market

This is also true for electric vehicle drives. Back when I had hair on my head and carried a slide rulethere were lead acid batteries, DC brush motors, and contactor controllers. Today, none of these remain including my hair. Lead has been replaced by lithium and DC by either DC brushless or induction. Contactors, meanwhile, have given way to modulating inverters. Without a good crystal ball, it is hard to predict the future. Each will have its loyal proponents and religious detractors.

A Closer Look So what are these two technologies? How do they work? What differentiates them? And what do they have in common? With brushless machines, the rotor includes two or more permanent magnets that generate a DC magnetic field as seen from the vantage point of the rotor.

In turn, this magnetic field enters the stator core a core made up of thin, stacked laminations and interacts with currents flowing within the windings to produce a torque interaction between the rotor and stator. As the rotor rotates, it is necessary that the magnitude and polarity of the stator currents be continuously varied — and in just the right way - such that the torque remains constant and the conversion of electrical to mechanical energy is optimally efficient.

The device that provides this current control is called an inverter. Without it, brushless motors are useless motors. A forerunner of the 3-phase induction motor was invented by Nikola Tesla sometime before By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. Adjust the frequency to get same amplitude on both resistor and the motor phase.

The slight rotor movements should not be a problem since it will not achieve any significant speed. I "think" inorder to calculate the inductanceyou have to know the number of turns and wires Gauge and other manufacturing properties of the motorwhich most likely are not available. What's the easy way to measure a DC hobby motor's inductance? You may need to add a small series resistance to measure the current - connect this in the ground supply line to the motor so that you can measure the voltage across it without shorting anything to ground.

And remember to include this resistance value in the time constant calculation. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. How can I calculate the inductance of brushless DC motor? Ask Question. Asked 3 years, 9 months ago. Active 3 years, 9 months ago.

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Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. Forgive me if I am asking something absurd, I really do not understand much about electric motors. No, a DC induction motor is not possible.

Induction implies causing current thru a magnetic field. Only varying magnetic fields can do that. This is also the same reason that transformers don't pass DC. There is no on-going power associated with a fixed magnetic field, just some fixed energy to hold it there.

If this weren't true, you could get ongoing power from a fixed permanent magnet. However, true DC motors are possible. In fact, the first real continuously running electric motor was DC. You can also make a disk spin by pushing DC current thru the disk radially, with a fixed magnetic field perpendicular to the disk.

The reason this is not usually done is because of the difficulty of electrically connecting to the outside edge of a spinning disk. However, it can be done and has been done. The reverse also works. A spinning disk with a fixed magnetic field perpendicular to it will develop a radial potential between axis and outer edge. There have been tachometers based on this principle. All electrical machines need an AC flux to couple the magnetic energy. DC brushed machines produce this via commutators.

Basically these are also AC, just expose a DC accepting connection. If you were to feed the machine with DC you would need some form of commutator to take that DC and alternate it to produce the required AC. Could this AC be enough to excite the rotor with an AC field? Imagine a mains transformer being excited with a squarewave, some energy does get transformed but not as much as if it was AC. Yes: but qualified. If you pound the string "ECM motor" into Google, you can learn how it's done and what the benefits are.

Yes,It's Possible,but not so efficient. You need two commutators to build such a motor. The first commutator receive current from source supply it to the rotating coil and second commutator.

And the second commutator supply current to the stationary coil. The impression of this kind of motor is given in this image. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Are DC induction motors possible?