VFD rather than VSD

[maypot]

Hi,

I have seen many posts using the term VSD rather than VFD.A variable frequency drive varies the frequency which is a vector quantity rather than speed which has got magnitude only and no direction.

Bob

 

[jraef]

Well, we accept that the term VFD can only refer to AC motor controls, so frequency is speed when implemented in the motor. The VFD also has to change voltage at the same time, and of couse the output pattern determines direction of rotation, but none of those can exist without the other. So VFD (as related to motor control) always means variable speed even if not stated. AFD means the same thing, but VFD is a more popular term.

VSD (as well as ASD) is actually a more generic term. It can mean a DC drive, an eddy current drive, a fluid drive or a mechanical variable pulley system such as a VariDrive or Variator. People use VSD quite often, but they really should probably be more specific since it can and does mean many things.

Inverter is another problematic term used a lot for VFDs. Technically, all VFDs have an inverter in them because that is the heart of the technology, but there is also a converter at the front end, and there are also plain inverters that are NOT VFDs. So again, it is technically too vague.

Side note:
To make matters worse, especially when searching the internet, VFD also means Vacuum Fluorescent Display, Voluteer Fire Department, Variable Field Data and a host of other non-motor related terms. Makes life interesting.

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[PowerfulStuff]

Hi,
Just one more from a long time ago - many older units were called VVVF drivess - Variable Voltage Variable Frequency. Probably more correct but I haven't seen it used for ages.

Regards,
Martin

 

[aolalde]

Hello Maypot:

The regional uses must influence the terminology. It depends on how generic or specific the drive description is intended. Some other examples are; AFC for Adjustable Frequency Controller, VVI for Variable Voltage Input driver, CSI for Current Source Input Inverter, PWM for Pulse Width Modulated Inverter, etc.
BTW (not a driver, but by the way) I do not consider frequency a “Vector” since vector quantities must have magnitude, direction and obey the parallelogram law of addition; like force, magnetic field, voltage differential, electric current, including velocity, etc.