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Using resistor and DC motor acting as generator as a brake

by Ry122
Tags: acting, brake, generator, motor, resistor
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Ry122
#1
Apr27-14, 06:26 PM
P: 517
how would you calculate the resistance required for a resistor which is in series with a generator (DC motor in reverse) to achieve a certain torque from the generator?
Eg, theres a torque of 30kN acting on a 100kW generator while it moves at 50RPM.
The is the same mechanism as electric diesel locomotives use to brake that employ rheostatic braking.
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Simon Bridge
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Apr27-14, 08:27 PM
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You have to ask yourself how much work is being done to run the generator circuit.
sophiecentaur
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Apr28-14, 06:34 AM
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Quote Quote by Ry122 View Post
how would you calculate the resistance required for a resistor which is in series with a generator (DC motor in reverse) to achieve a certain torque from the generator?
Eg, theres a torque of 30kN acting on a 100kW generator while it moves at 50RPM.
The is the same mechanism as electric diesel locomotives use to brake that employ rheostatic braking.
If this is a real, practical problem then the motor would need to be a suitable one. Many motors will not work as generators, particularly not high power motors, with field windings.
Your suggested 100kW generator is quite a meaty piece of kit.

Note. If you want to calculate power (in Watts), as Simon B suggests, you will need to convert your RPM to angular velocity (and get your Torque in the right units, too - do you mean kNm?)


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