How Can I calculate bank of resistor to eletric motor whit winding rotor???
How Can I calculate bank of resistor to eletric motor whit winding rotor???
(OP)
I don´t know, How Can I Calculate bank Of resistor to electric motor whit winding rotor
Can you help me????
Thanks.





RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
Eugene C. Lister's "Electric Circuits and Machines," Sixth Edition, McGraw-Hill, C. 1984, pgs. 398-399, gives a general description of how industrial electronics can be harnessed to provide smooth wound-rotor motor starting while incorporating highly efficient slip power recovery and regenerative speed control.
In other words, it's been more than 25 years since starting resistors became obsolete; it's time to move on.
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
How does... one calculate the resistance required?
There is... indeed... a trend to retire slip-ring motor applications... and yet... they are still out "here".
Is there a "boiler plate" answer to this post?
Always enjoying this forum,
John
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
However! We are derailing the OP's post and he's clearly struggling with the English language so let's not make things more difficult for him than they already are.
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
The hard way is to use these 2 facts and and calculate them yourself. The rotor voltage is inversely proportional to speed or proportional to slip. The rotor current is proportional to torque output. Pick the number of steps and then calculate the resistor needed to bring the motor to the maximum speed for each step.
The EASA Technical Manual has a section on calculating the rotor resistors to start a motor. The basics are to take the secondary phase voltage and divide by phase current to calculate the total rotor resistance. Don't use the phase-to-phase voltage that is typically given on the nameplate - divide that by sqrt(3) first. Use the following table to calculate the starting resistance steps as percentages of this total resistance.
2 steps - 70 & 30
3 steps - 55 & 30 & 15
4 steps - 40 & 30 & 20 & 10
5 steps - 34 & 26 & 19 & 13 & 8
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
these are the details of my electric Motors:
Electric Motor with winding rotor
3 Phases
KW: 15 Kw
stator Voltage : 440 Volts
Stator Amperes: 33 Amperes
Frecuency: 60 Hz
855 RPM
Voltaje Rotor : 187 Volts
Amperes Rotor: 55 Amperes
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
Don't worry, neither can I - not without digging in to some very old texts to help.
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
I posed how to calculate the resistors for motor starting. It's rather simple to do. I'm not providing resistor numbers to the original poster unless he understands what they are for. At that point, he can calculate them himself.
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
If rpm[mec]=855 wsync=900 then sn=0.05
Since , Pgap=3*Irotor^2*Rrotor/s then Rrotor=Pgap*sn/3/Irotor^2
Pgap=Pmec/(1-sn)=15789 w
Irotor=55 A will get Rrotor=0.08699 ohm.
But Irotor=Erot*sn/sqrt(Rrotor^2+Xrotor^2*sn^2) then Xrotor=sqrt(Vrot^2*sn^2/3/Irot^2-Rrot^2)/sn=0.9089 ohm
This wound rotor resistance and reactance usually does not present big difference from start up to rated rpm. Then for each step the rotor current will be:
Irotor=s*Vrot/sqrt(3)/sqrt((Rrot+Rext)^2+Xrot^2*s^2)
Pgap=3*Irot^2*(Rrot+Rext)/s
Let's take Rext total=1.7 ohm and let's take 5 steps as follows:
rotor current will be:
Irotor=s*Vrot/sqrt(3)/sqrt((Rrot+Rext)^2+Xrot^2*s^2)
Pgap=3*Irot^2*(Rrot+Rext)/s
Let's take Rext total=1.7 ohm and let's take 5 steps as follows:
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
7anoter4.
Ok thanks, the most important is your intention
Thanks
Best Regards
RE: How Can I calculate bank of resistor to eletric motor whit winding rotor???
Personally, I have achieved what I needed to achieve (not necessarily what you need to, though it sounds somewhat similar) through creating an equivalent circuit of the motor and adjusting the "R" of "R2/s" as required / observing the impact on the key parameters.
Regards,
Lyle