Do electric engines(locomotives) have gears for speed control?

Question

do electric engines have gears for speed control.?? if not how do they control the speed in these engines

Answer 1

Electric locos do not use gears for speed control.  This would offer limited power 'steps' and much more mechanical components to go wrong and wear.

There are two ways in which electric locos control their speed:  Voltage regulation for DC motors.  Frequency regulation for 3 phase AC motors.

With the DC motors, voltage can be controlled by using resistors, thyristors and tap changing on the main transformer.

For the AC motors, a DC supply must be used and fed to the motors were an Inverter.  The inverter converts DC into AC and can vary the frequency and thus the speed.

Answer 2

No.  They don't need them.  The electric motors are fully controllable at all speeds and speed is managed electrically.  Most such motors are direct current.

Incidentally, it is correct to refer to an electric locomotive as a "motor" rather than as an "engine."

Diesel electric locomotives typically control the speed by varying the revolutions of the diesel engines which turn generators to make the current for the traction motors.

Many traction motors are geared, but this is for variation between motor speed and wheel speed rather than for speed control.

Answer 3

Found the link - its describing the noise but explains about about the speed control

The noise you hear has nothing to do with physical gear wheels. The torque and speed of an asynchronous motor is governed by the frequency of the alternating current feeding it, which itself is created by switching DC using something like a GTO inverter. As the train picks up speed, the frequency of the AC must increase, and it is parts of the train (I suspect a transformer but it may be the motors themselves) resonating at this frequency which makes the noise like a car acclerating, and at certain speeds/power notches the AC pulse sequences change, it is the change in these that causes the step change in resonance noise that sounds like a car changing gear.

Answer 4

I just need to correct a correction from Warren D..............

Engine : " A unit propelled by 'any form of energy', or multiple units operated from a single control, used in train or yard service. "

Though he is correct electric locomotives are commonly referred to as a "motor", and the person operating them is "a motorman", but these terms usually apply to underground operations.  If you see and electrified passenger train on the surface, such as an Amtrak train, it is being pulled by an engine and an engineer is at the controls.

Answer 5

the electric trains I drive use AC motors and use Thyristors and not gears. The thyristors make a very unusual noise that sounds a lot like gears changing (which they aren't!)