How do induction motors vary frequency?

Thus, the speed control of an induction motor using a variable-frequency supply requires a variable voltage power source. The variable-frequency supply is obtained by the following converters. An inverter converts a fixed voltage DC to a fixed or variable voltage AC with variable frequency.

What is the frequency of the induced emf in an induction motor?

The induced emf frequency is slip times the frequency of applied voltage. Since emf in induction motor is induced when stator flux cut the rotor conductor so the emf actually is induced only due to their relative speed i.e Ns-Nr (Ns=synchronous speed of stator flux and Nr=rotor speed in RPM) between them.

Why do induction motors vibrate?

In the Vibration in an Induction Motor tutorial model, eddy currents are induced in the rotor by time-harmonic currents in the stator windings and rotation of the rotor. The air gap between the rotor and stator is asymmetric, resulting in vibrations in the motor.

How does the frequency effect change the motor speed?

A frequency higher than the rated frequency usually improves the power factor but decreases locked-rotor torque and increases the speed and friction and windage loss. At a frequency lower than the rated frequency, the speed is decreased, locked-rotor torque is increased, and power factor is decreased.

How do induction motors reduce vibration?

An easy method to reduce vibration is to install a clean damper on the rear shaft of the motor. Clean dampers are basically hermetically sealed plastic cases with an inertia body packed with silicon gel. The extra inertia and silicon gel help absorb the vibration and provides a stable damping effect.

What makes a motor vibrate?

Vibration can be caused by one or more factors at any given time, the most common being imbalance, misalignment, wear and looseness. Misalignment /shaft runout – Vibration can result when machine shafts are out of line. Angular misalignment occurs when the axes of (for example) a motor and pump are not parallel.

What happens if an induction motor runs below its rated frequency?

If the induction motor runs below its rated voltage, the flux will reduce and as a result, the torque delivering capacity of the motor will get reduced. If the motor drives the same load at reduced voltage, it will draw more current and will get overload tripped.

How does frequency control motor speed?

V/Hz control maintains a constant ratio between voltage (V) and frequency (Hz). Varying the voltage frequency affects both the motor speed and the strength of the magnetic field. When the frequency is increased (for higher motor speed), the magnetic field decreases, and lower torque is produced.