Speed controller VS Frequency inverter ?

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"A frequency inverter changes output voltage frequency and magnitude to vary the speed, power, and torque of a connected induction motor to meet load conditions. A typical frequency inverter consists of three primary sections...

Frequency inverter also called frequency converter, it is a power control conversion device to convert normal power supply (50Hz or60Hz) to another frequency ...

An electronic speed control or ESC is an electronic circuit with the purpose to vary an electric motor's speed, its direction and possibly also to act as a dynamic brake. ESCs are often used on electrically powered radio controlled models, with the variety most often used for brushless motors essentially providing an electronically generated three phase electric power low voltage source of energy for the motor.

An ESC can be a stand-alone unit which plugs into the receiver's throttle control channel or incorporated into the receiver itself, as is the case in most toy-grade R/C vehicles. Some R/C manufacturers that install proprietary hobby-grade electronics in their entry-level vehicles, vessels or aircraft use on board electronics that combine the two on a single circuit board."

One changes the speed and one changes the frequency (50 to60 Hz)

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with answer of ...

 Elke Woofter

The Speed Controller may be using AC or DC Motors but function remains the same that is to vary speed of motor with maximum available torque

Frequency inverter control’s the Frequency in Hz w.r.t to voltage to achieve variable speed of an induction motor without compromising its maximum torque

We Know that F=PN/120   this3 phase motor speed control formula is a very important formula for speed control of a motor

The Function of both the VSD and VFD is almost the same but VFD is more superior in some respects and is the latest technology available 

I endorse MS.elke answer 

Thanks

Speed controller control the voltage but in frequency inverter drive control v/f ratio.

In the market of speed control units for fan drives, it is self-evident that they must work efficiently and without noise emissions. To fulfil these requirements, and to be able to offer an ideal system consisting of motors and frequency inverters, ZIEHL-ABEGG SE in Kuenzelsau, Germany, has developed the range of Fcontrol frequency inverters. These frequency inverters with an integrated all-pole effective sinusoidal filter, enable the motor to run efficiently and free of electro-magnetic noise.

Thanks for the invitation. But I do not have any idea to answer this question.