Can VFD be set for 3 different speeds with 3 different time & load cycles in a full duty cycle? 6

[edison123]

Can a VFD be set for 3 different speeds and 3 different time & load cycles of

x1 RPM/t1 sec/a1 amps

x2 RPM/t2 sec/a2 amps

x3 RPM/t3 sec/a3 amps in a full duty cycle?

Motor capacity is 5 KW, 6 pole, 50 Hz with external blower for cooling.

Muthu

http://www.edison.co.in

 

[iop95]

Hi edison,

There are input data as torque and speeds.
For direct motor drive (no gear), need to choose best motor design that cover these data.
As original motor has very low efficiency at low speed (about 5%)... output power was limited by lack of cooling with such high input current.

With VFD at same low speed and same torque, current will be much lower.

If want to avoid any forced cooling (I don't think will be needed, but must check loses and fan airflow at low speed), may increase pole number as Lionel suggested.

Also, if is possible/customer accept, may increase VFD/motor operating frequency (with or without motor base frequency) and use a fixed gear; in this way motor will run at higher speed (double for example), cooling is better and may reduce cooper wire diameter... or increase operating temp condition.

 

[edison123]

The 3 speed motor already has an external axial blower but given the size of the motor (270 mm dia) and poor cramped design of frame, air velocity not great.

I have pitched the idea to the client, who promised to get back to me. Meanwhile, I will talk to local VFD vendors to see if they are willing to do this exercise. (My part is simple and easy while theirs is more arduous)

Thank you again all for your great inputs.

Muthu

http://www.edison.co.in

 

[CelsoSC]

If multi-step speed selection on a VFD is not enough to select fixed speed settings for the motor and you need to define special conditions for each speed step, then a VFD with Parameter Sets can be used.
Where each set can be configured as a different motor, up to four different sets, some brands can have eight different sets. A lot of German VFD brands have Parameter sets.
This is used, for example, in some Edge banding machines, where groups of motors are switched on in different combinations, so current limits and speeds can be adjusted for each different combination.
And you can use just one Vfd for all different motors.