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I want to simulate a motor with a resistor and inductor. It means I want to connect a resistor and inductor to 1-phase or 3-phase instead of a motor.

For achieving this goal I have to measure both active and reactive power and calculate the value of resistor and inductor. Is it possible? I mean is it a right way to consume active and reactive power with resistor and inductor?

And if it is right, how is the connection of resistor and inductor, parallel or in series?

ocrdu
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Hamed P
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  • What about back EMF? – user57037 Feb 17 '19 at 05:55
  • I just want to consume active and reactive power – Hamed P Feb 17 '19 at 06:00
  • The resistor should consume some power. But it is not clear what your goal is. Maybe experimenting with a simulator would help you accomplish your goals. – user57037 Feb 17 '19 at 06:04
  • And how about inductor? I want to test my measuring instrument – Hamed P Feb 17 '19 at 06:05
  • Real inductors consume some power, because they have series resistance and core losses. But ideal inductors do not consume power. They temporarily store energy and release it later. – user57037 Feb 17 '19 at 06:07
  • If I connect a 100uh 10A inductor in series with a 500wat resistor is it possible? – Hamed P Feb 17 '19 at 06:12
  • I am having trouble following you and understanding your intention. Of course you can connect them in series. But how many Ohms is the resistor? What DC or AC voltage will you apply to the inductor and resistor? Why would you do that? You can easily calculate exactly what will happen without actually connecting them using simple math. There is no need to re-discover Ohm's law. – user57037 Feb 17 '19 at 06:15
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    You can put the components in either series or parallel, and calculate how much actual and reactive power they will consume, in order to test your meter. Then having gained confidence in your meter, you can use it to measure your motor. Is that what you want to do. – Neil_UK Feb 17 '19 at 06:15
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    As Neil said I want to test my meter and I wanted to know if it measures the reactive power right or not. And I don't have any motor or other devices that consume reactive power and I thought of using inductor instead of a motor – Hamed P Feb 17 '19 at 06:23
  • sure, an inductor is a good load for testing a meter, any large transofrmer will do. if you have a variac, microwave-oven transformer, or large isolating transformer they would make good test loads, (the microwave oven transformer can produce a few kilovolts so be sure that the secondary terminals are well insulated) – Jasen Слава Україні Feb 17 '19 at 06:51
  • Thank you, Jasen. Do you know a motor inductance value? – Hamed P Feb 17 '19 at 06:55
  • motors aren't like inductors, if you want to test a motor use a motor. eg a drill presses, bench grinders, and pedestal fans typically hae induction motors. – Jasen Слава Україні Feb 17 '19 at 07:25
  • I don't want to test a motor, I want to consume reactive power and measure it with my meter and because of that, I want to use an inductor. Is it possible? – Hamed P Feb 17 '19 at 07:29
  • yes. it's possible. – Jasen Слава Україні Feb 17 '19 at 07:38

2 Answers2

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Since I can not comment, I will post my comment as an answer. I concluded that you do not have a lot of experience since you posted this: "If I connect a 100 μH, 10 A inductor in series with a 500 W resistor is it possible".

From your initial question I deduced that you want to connect the resistor and inductor to the mains voltage, do not do this without knowing the resulting current.

Preferably, do not do this with the mains voltage at all; get a signal generator. Depending on the frequency of the signal you are working with calculate the inductor impendance \$ Z=\omega\cdot L \$, and make sure the inductor is within its limits. Next choose a resistor with approximately the same resistance in ohms as the inductor. Connect them in series or parallel and work with that.

ocrdu
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Ziggy
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  • Thanks for your reply. As you said I don't have enough experience in this field. Is it important that the resistor and inductor be in the same value? – Hamed P Feb 19 '19 at 17:37
  • The resistance of the resistor should be about the same value as the impendance of the inductor at the given frequency. This assures that the voltage across each of them is about the same when they are connected in series, and your measurements will therefore be more accurate. – Ziggy Feb 20 '19 at 09:09
  • Thanks for the useful information. I want to test it with 3-phase and it seems it's a little dangerous! what is your advice for me? – Hamed P Feb 20 '19 at 09:50
  • Get an ac power source with current limiting, or use somthing like this: [link](http://www.farnell.com/datasheets/2305524.pdf), just make sure you dimension the components(the resistor and inductor) so that the resulting current the source provides does not exceed its limit, and the current trough the individual components does not exceed the components limit. – Ziggy Feb 20 '19 at 10:53
  • Thank you, Ziggy. I will test it and share the results. Can I have your email or something else to get in touch with you? This is my Gmail: hpexeph@gmail.com – Hamed P Feb 23 '19 at 07:39
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You are assuming that the motor is equivalent to a resistor and inductor. That is not a given. If you use a three-phase synchronous motor without load, there is an excitation of the rotor where the motor will consume only real power. With underexcitation, the consumption will have an inductive component. With overexcitation, the consumption will have a capacitive component. Large idling synchronous machines are traditionally used for power phase compensation purposes in either direction. The temporary storage of energy necessary for reactive power consumption other than the natural inductivity is done with rotational inertia, so you may need flywheels and good bearings for best results in that capacity.

Rotational inertia makes for a lot of the electrical behavior of motors, so a replacement by static components is only a reasonable approximation for stationary behavior and even then will not be a good model of the harmonics that may occur.

Starting and behavior under changing mechanical loads is not really easy to model with passive circuitry.

user107063
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