A two-phase motor is a system that has two voltages 90 degrees apart, which is no longer in use nowadays. The alternator is composed of two windings placed at 90 degrees from each other. They require 2 live and one ground wire that work in two phases.
Three-phase motors are motors designed to run on the three-phase alternating current (AC) power used in many industrial applications. AC electricity changes direction from negative to positive and back many times a second.
The stator is made up of a number of stampings in which different slots are cut to receive 3 phase winding circuit which is connected to 3 phase AC supply. The three-phase windings are arranged in such a manner in the slots, that they produce a rotating magnetic field after AC supply is given to them.
Single-phase induction motors are used extensively for smaller loads, such as household appliances like fans. Although traditionally used in fixed-speed service, induction motors are increasingly being used with variable-frequency drives (VFD) in variable-speed service.
Variable frequency drive VFD is the best way to
control the speed
of three phase motor.
The speed control of three phase induction motor from stator side are further classified as :
- V / f control or frequency control.
- Changing the number of stator poles.
- Controlling supply voltage.
- Adding rheostat in the stator circuit.
Slip in Induction Motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. When a three phase power supply is connected to the three phase stator winding of induction motor, a rotating magnetic field is produced in the air gap.
At high speed, this motor provides more power than a same-size induction motor but is not maintenance-free. The AC line is directly connected to the stator of a repulsion motor with the commutator shorted by the brushes. Retractable shorted brushes may start a wound rotor induction motor.
In AC induction motor, two windings in stator create a rotating magnetic field, which makes the rotor rotate. So there is no need of supply to rotor and hence no commutator. However, in series motor, available for both AC and DC supply, commutators are used to supply current to rotor windings.
AC induction motors have no brushes and have a much longer life expectancy. DC motor speed is controlled by varying the armature current, while AC motor speed control is achieved by varying the frequency of the alternating current, often with a variable frequency drive(VFD).
The types are: 1. Resistance-Start Single-Phase Induction Motor 2. Capacitor-Start Single-Phase Induction Motor 3. Capacitor-Start Capacitor-Run Single-Phase Induction Motor 4.
A synchronous motor is a doubly excited machine, whereas an induction motor is a single excited machine. In case of Synchronous motor its armature winding is energized from an AC source and its field winding from a DC source, whereas in case of Induction motor its stator winding is energized from an AC source.
An AC motor works by applying alternating current to stator windings, which produce a rotating magnetic field. Because the magnetic field rotates in this way, an AC motor does not need power or mechanical aid to be applied to the rotor.
Set your multimeter to Ohms. Start by completely disconnecting the spindle motor from all power sources. Check each wire, including T1, T2, T3 and the ground wire. If the reading is infinite, your motor should be fine.
In AC induction motor, two windings in stator create a rotating magnetic field, which makes the rotor rotate. So there is no need of supply to rotor and hence no commutator. However, in series motor, available for both AC and DC supply, commutators are used to supply current to rotor windings.
AC motors are constant speed devices but their speed can vary if you change the input voltage or frequency or the windings that make the motor rotate. The most common and efficient way of changing the speed is to vary the frequency by using an inverter as the power supply.
A couple of things you can do:
- Use gears to change ratio of speed, which is what you're going to do.
- Use a stepper motor, which are commonly used for high-torque, low RPM applications.
- Find some sort of PWM control circuit to slow it down, although you probably won't be able to get it down to 5-10RPM.
If you want to reduce rpm without compromising speed regulation then use a voltage regulator or PWM controller to lower the motor voltage. If you also want higher torque then use a gearbox (which increases torque by the same proportion as it reduces shaft rpm).
There are several ways to control the speed of an induction motor.
- Reduce the voltage applied to the motor.
- Control the current to the motor.
- Use a wound-rotor motor and control the resistance applied to the rotor windings.
- Control the frequency and voltage applied to the motor.
Speed of an electric motor can be decreased reducing current, it can be done either introducing a resistance or an inductance(choke coil) in series with the circuit but it will decrease it's power. If you need less speed in an outer circuit then use a gear system, it will not decrease it's power.
Three Ways to Control a Single-Phase Induction Motor :
Either by adding extra windings, external relays and switches, or by adding gear mechanisms, the direction of rotation can be changed. Using microcontroller-based control systems, one can add speed variation to the system.Increasing the voltage above the rated voltage increases the speed only slightly and is also much affected by the load. Increasing the voltage by much more than 5% will cause excessive current and overheat the motor. Increasing voltage increases magnetizing current thus increasing magnetic flux.
