Motor choice for VFD convertion?

umnik

umnik

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Guys,
I have a question about motor choice for converting machinery to variable speed.
My story. I have 16-speed (belt changes) drill press, which I love but HATE belt changes. Read a lot about VFDs. Went ahead and bought TECO L510 vfd and RELIANCE AC MOTOR 3/4 HP 3PH. When everything was done I was excited with results though still left with one big BUT! Lower speed torque is pretty weak and if I use large whole saws or fostner bits the drill press bogs down and I have to bump up the speed to keep it going. That is pretty frustrating. I strated to look if anything can be improved and found stories about inverter rated motors. My current motor is relatively old basic motor without any fanciness. My question is If I will swap it out for let say Baldor IDNM or similar inverter rated motor will it improve low speed torque noticeably?
 
Try setting parameter 00_00 to 1. This puts the VFD into sensorless vector mode (SLV mode). This should give you 100% torque at near zero RPM. This will require some additional setup in the parameters to auto tune the VFD to the motor. See the instructions in the 02 parameter group.
 
Jim,
thank you for the hint. Yes, it's already in slv mode, but still weak. Putting in slv mode improved performance just a little bit though unnoticeable.
 
Changing the motor for the same HP won't help. Look at the torque boost for SLV mode. Also double check the general motor parameters. Another thought is that the motor could wired for high volts rather than low volts, might be worth checking that.

Or it could be that the motor is just under powered for what you are trying to do with it. :) The 3 HP on my mill runs out of power when tapping 1/2-13 holes in steel, when not in back gear.
 
I tried every option in my VFD to boost torque but no luck. The motor is dual voltage and I wired it accordingly. My drill press had 3/4HP motor which never felt weak, so I picked up 3PH motor with similar power rating. Probably only higher powered motor only the option.
 
For more Torque go for more poles on the motor..
8 pole motor is 750rpm @ 50Hz /1500 rpm @ 100Hz

0.75kW 3PH motor spec.

8 pole motor 5.05Nm - 0.04kW (0.05HP) x 71 RPM at 5 Hz

6 pole motor 3.87Nm - 0.04kW (0.05HP) x 93 RPM at 5 Hz

4 pole motor 2.5Nm - 0.037kW (0.05HP) x 141PM at 5Hz

2 pole motor 1.26Nm - 0.0375kW ( 0.05HP) x 284 RPM at 5 Hz
 
umnik said:
I tried every option in my VFD to boost torque but no luck. The motor is dual voltage and I wired it accordingly. My drill press had 3/4HP motor which never felt weak, so I picked up 3PH motor with similar power rating. Probably only higher powered motor only the option.
Click to expand...


Did you buy a 1800 (4 pole) or 3600 (2 pole) RPM motor? You may have to try a different pulley ratio to get the performance you want.
 
I guess I would set the belt speeds to a mid range and see what difference that makes.
 
I put a 6 pole (1140 rpm) motor on my drill press. It brought the overall rpm down usefully and definitely makes more torque than the original motor. VFD's are great, but there's a limit to what you can expect from them.
There's still some belt changing in your future. :)

Some folks use variable speed D.C. motors for that sort of thing.
 
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