# PMAC machine regenerative braking question

Discussion in 'Electrical Engineering' started by johnoshea19@gmail.com, Aug 17, 2013.

1. ### Guest

Hi,

I was wondering if you might be able to help me with the following question.

An electric drive operates in regenerative braking mode and has a regenerative torque of -50Nm @ a speed of 4775rpm (500 rad/s.

The electric drive features a three-phase four-pole PMAC machine. This machine can be modelled as Rs (per phase stator resistense = 0.01ohms), Ls (per phase synchronous inductance = 0.1mH) and the machines per phase back emf in series.

The machine constant (k) is 0.07V/rad/s and the no load torque is 5Nm.

The phase current is vector controlled to be 180 degrees out of phase with the back emf when in regenerative mode.

The battery has a no load voltage of 360V and an internal resistence of 0.1 ohms

The inverter is 97% efficient.

How would i get the: (i)per phase voltage and current output by the motor, (ii) moter power factor and efficiency and (iii) battery current and battery power.

any help you could give me would be greatly appreciated especially with how the current being 180 degrees out of phase with the back emf would effect things.

kind regards,
John

, Aug 17, 2013

2. ### Guest

I think to find the per phase current, the following is correct.
Iph = TEM/3k
TEM = TR+TNL = -50+5 = -45Nm
therefore, Iph = 214.29A

, Aug 17, 2013