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I am trying to learn about the torque profile of two coupled machines. I believe that if a DC motor is driving a DC generator of identical ratings, the generator will exert rated torque on the motor if it is supplying rated load current. Moreover, the torque profile will be constant.

Suppose that the DC generator is replaced by a synchronous generator, and the generator drives a three phase resistive load (Y or delta).

(1) Will the generator exert sinusoidal torque on the DC motor's shaft?

(2) What will be the torque profile if the load is unbalanced?

(3) What will be the answer to (1) and (2) above, if the synchronous generator is replaced by a 3-phase BLDC machine?

Thank you very much for your helpful inputs!

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  • \$\begingroup\$ I built a simulation with a 15W BLDC motor driving an identical BLDC machine (slave), and hooked up three 5 ohm resistors in series with the slave BLDC winding. I changed one of those resistor values to 1 ohm, resulting in a huge torque ripple by the slave machine had a huge ripple. I guess this was primarily because of unbalanced phase currents flowing in the machines. \$\endgroup\$ – Adeel May 5 '15 at 12:01
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  1. theoritcally there is always a hormonic torque exerted by AC generator but very small upto 4% at 6 th horminic for 3 ph. suply however, the inertia of the system tales care of such fluctuation..whereas, resiprocating compressors exert fluctuating torque and one has to have flywheel.
  2. if load is unbalace such fluctuating torque would increase..i.e. negative sequence.
  3. BLDC is generally ref. to a Motor.. VTIngole
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  • \$\begingroup\$ and BLDC machines can be used as a generator. All they are a magnetically shaped Permanent Magnet Sync Machines. All electrical machines can be used as either a motor or a generator. \$\endgroup\$ – JonRB Aug 16 '15 at 12:24
  • \$\begingroup\$ Yes, it can work as a generator..a three phase depending on the winding profile.. Vtingole \$\endgroup\$ – vijay ingole Aug 18 '15 at 14:51
  • \$\begingroup\$ not at all. if you can operate it as a motor you can operate it as a generator. \$\endgroup\$ – JonRB Aug 18 '15 at 15:06

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