Three phase AC motor model problem...

Hello, is there a way to use the 3PH_Motor from the family OUTPUT_DEVICES located in the group Electro_Mechanical but with a modified Spice model that uses only the data printed on the nameplate? I ask this question because I have to simulate power factor correction using a field of 10 motors rated at 110 kW each for my thesis, but I need the R and L of the windings in order to use the default model and I cannot find these values in catalogues.
Thank you in advance and I hope there is a way to solve this problem...
Multisim 12.0.0
Solved!
Go to Solution.

I am assuming you're looking for an induction motor.
It would be an oversimplification to model an induction motor using a fixed R,L load (In V12 of Multisim, we actually removed the 3PH_Motor and instead added a more realistic dynamic model based on a more realistic parameter set). An induction motor is in many ways like a transformer. Therefore you need the magnetising inductance, rotor and stator leakage inductances, and rotor and stator resistances. You may be able to contact the manufacturer to obtain, but I doubt you can accurately deduce them just from the name plate.
This link goes over a simple steady-state model: http://www.scribd.com/doc/13311930/Induction-Motor-Modeling-steady-State
Thanks,
Max
National Instruments

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Hi everyone,
I'm trying to measure the phase and the power factor for a three-phase motor. The problemn is that the motor is running with 480V and the SCXI module that I have can only handles until 300Vrms. I'm thinking about using some voltage transformers to step down the voltage and then connect it to the SCXI module. If I do that, will it affect my phase angle and power factor?
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Just want to emphasise Lynn's point about 480 nominal volts and what you might actually have.
Get your design and wiring checked by someone certified to do so before connecting.
Some further points:
How is the motor being fed?
a. If fed by a Direct On-Line starter or a Star-Delta starter, there will be a big spike when the contacts open to turn the motor off, or during the star-delta transition.
b. If fed by a PWM inverter, then the inverter synthesises the AC 50 or 60 Hz wave form by chopping DC very fast, and relying on the motor windings to act as the low pass filter. Good luck trying to instrument that.
Fault Level: You must have fuses as close to the instrumentation pick-off point as possible. That way, if there is a fault in your wiring the instrumentation fuse pops, and you do not have the full fault current flowing through your instrumentation wiring. Fault current will probably be about 4 times motor start current if the motor is fused correctly, and if it is an induction motor.
I would use isolation amplifiers on the voltage inputs. That way you can use a simple potential divider on the input to scale to the voltage you want, but make sure that the isolation amplifier has a suitable frequency range.
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How can I calculate the frequency of a 2-4Hz three phase sine wave in 50msec?

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Three-Phase Power Analyzer, Etc.

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diarmaede wrote:
Hi All,
I'm not sure if this is the right board for this question, or if I should ask it on one of the hardware boards. Let me know if I should move it, please.
I need to set up a LabVIEW-based system to monitor the following:
1. Output from three-phase power analyzer (480VAC, 0-100AAC) - this could involved monitoring formatted power-quality data from a power analyzer OR monitoring voltage and current on all phases, then doing the power quality calcs in LabVIEW
2. DC output current (0-200ADC) - This needs to be relatively fast (2000 samples/sec), but not very precise (0.1A resolution would be fine).
3. DC output voltage (0-600VDC) - Again, this needs to be fast but not very precise. See current specs, above.
4. CAN bus - I'll be monitoring a CAN bus and processing CAN data, probably using an NI USB-8473. I have much of the CAN code written already.
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Many thanks in advance.
Hmm... I have used a few three phase power analyzers from Voltech, Valhalla, and Yokogawa with LabView.
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How to acquire correctly three-phase signals (Problem with the gap between signals)

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Duplicate Post
Cory K

A/C three Phase motor control using 1/4 bridge Load Cell output and a USB 9172 Daq

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Should I use Case Structures and then place them in a while loop?
I setup a drawing in Word to visually define the task.
Signed,
Patrick Murphy
Attachments:
Layout for Testing Spars.docx ‏15 KB

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Three phase AC motor model problem...

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