In electric train what type of motor is used whether it's an AC or DC input?
It depends whether or not you are talking Lionel or General Electric. Lionel toy trains are DC. General Electric commercial trains are diesel-electric with modern ones generating on-board AC, converted to DC, converted to AC to drive the motors.
AC motors do not have speed control, so DC motors are used here. Yes the supply is AC, so we have to convert it into DC before connecting the motor to it.
Most modern locomotives use ac and you can get perfectly good speed control. There are still a few legacy dc systems including the London Underground.
An ac supply is usually used as it allows supply of low current.
