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# Re: [femm] complex torque

- To: femm@yahoogroups.com
- Subject: Re: [femm] complex torque
- From: David Meeker <dmeeker@ieee.org>
- Date: Thu, 02 May 2002 21:33:02 -0400
- References: <20020430085135.97625.qmail@web11002.mail.yahoo.com>
- User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.0rc1) Gecko/20020417

smaïl mezani wrote:

> `Hello folks,
> When calculating a torque from stress tensor of an
> induction motor, two values are displayed :
> - a DC torque
> - a double frequency torque in complex form
> So, what is the meaning of the complex torque and how
> is it cmputed?
> Thank you for any comment.
> `

All of the elements of the stress tensor contain flux density squared. When you do a harmonic analysis, you are the flux density varies sinusoidally at a frequency of w. When you square a sinusoidally varying quantity, you get one component at DC, and another component at 2W. The program is just computing both of these component. The 2x part of the torque is a complex value--the abs of the 2x force represents the amplitude of the 2x force, and the arg of the 2x force represents the phasing of the force. If F2x is the complex-valued 2x force, you'd represent it in terms of time as Re[F2X (Cos[2Wt]+j*Sin[2Wt])]
Anyhow, also check out:
http://groups.yahoo.com/group/femm/message/994
Also, you'd asked, in msg 1207:
`> Of course, it is easy to model the induction motor
> when imposing source currents.
> But, the motor is generally supplied by a sinusoidal
> voltage. So, what is "gradV" to be imposed to take
> into account a voltage source?
`
The voltage gradient only works with solid conductors, not wound coils. What you have to do is apply some currents and solve the problem. Then, evaluate the flux linkage of a phase and multiply by the frequency to back out voltage that was required to drive the current.
Arrgh. I really need to make an example of a 3-phase induction motor.
Dave.
--
David Meeker

- References:
  - complex torque
    - From: smaïl mezani <s_mezani@yahoo.fr>

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