VFD - variable frequency drive. They are more efficient than mains powered motors and are used in HVAC applications.
> ---------- > From: Matthias R. Heinze[SMTP:[email protected]] > Reply To: Matthias R. Heinze > Sent: Saturday, July 25, 1998 3:51 PM > To: Pryor McGinnis; [email protected] > Cc: Vitaly Gorodetsky; Emiko Parise; Charles Goertz; Chan Wang; Wilfried > Beyer; Phillip Hatton; Udo Heinz; Larry Fry; Klaus Ehrlich; Thomas > Dickten; Merwan Sukhadwalla; Andras Szende > Subject: Machinery Stop Modes > > I wish I knew what a VFD is. > However I can assume that you want to create a Category 1 a controlled > stop > (terms per IEC204, check also EN418). This is perfectly ok with most > machinery standards if the operation (and safety requirements) dictate the > use of such stop. The validation of this could for example be done using > EN1050. Just remember that Category 0 (uncontrolled stop or removal of > energy to hazard) stop must be implemented after the controlled stop. > For machinery safety I would look at ANSI or NFPA standards (NFPA79 is > generally the best choice, it is also somewhat aligned with IEC204) > standards. > > Matthias R. Heinze > Industrial Machinery Division > TUV Rheinland > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Pryor McGinnis > Sent: Friday, June 19, 1998 11:37 AM > To: [email protected] > Subject: Machinery Stop Modes > > > I have a client with the following question on stop modes for machinery. > > I have a VFD which has a RUN input which when closed is configured to > command the VFD to follow the DAC speed reference. When open, the VFD is > configured to ramp stop. I have this input tied to my overload circuit > such > that a mechanical overload will open the circuit and cause the motor to > ramp > stop. I have a sharp deceleration such that the motor will stop in the > shortest distance possible. > > When I E-Stop the machine, power is removed from the VFD. The motor (due > to > inertia) will coast some distance when power is removed from the drive in > and E-Stop condition. The drive control is lost in this mode thereby > eliminating the possibility of ramp stopping the drive. > > I want to design in a delay so that I can open the RUN input before > removing > power from the VFD in an E-Stop or overload condition. My thinking is that > I > can then ramp the drive down faster than just removing power from the > drive. > > I have a time delay module which can be fitted to the main drive > contactor. > This module gives me a .3 - 3 sec adjustable time delay. My thinking is > that > when the safety or overload string drops out, the control power (switched > 24 > vdc) is lost thereby dropping out the power to the run relay and power > contactor. Since the run relay drops out first, the drive will ramp down > before the power contactor drops out. > > My question to you is: Is this allowable in CE and U/L? > > I believe that this approach is acceptable as long as a risk assessment is > performed in accordance with EN 1050. > > Does anyone out there have a perspective on this issue? > > > RCIC - http://www.rcic.com > Regulatory Compliance Information Center > > > >
