VFD questions

[yota]

I assume this is the correct forum to discuss VFD's. please correct me if I'm mistaken.

thinking about converting my 1940's Delta 17" drill press to a 3-phase motor with a VFD to control RPM's. I have absolutely no skills with electronics so have a couple of questions to start.
1. is the 1.5hp motor pictured a good candidate for this? my understanding is that you want more HP than originally as the VFD can cost power or torque. my current original Delta repulsion-induction motor is 3/4hp. the motor pictured may be more power than needed but is available locally at a great price.

2. I have done some reading on VFD's and see some that some are 115v single phase input and some are 220V single phase input. I have both 115 and 220V receps next to my drill press currently so can use either. is there any advantage or disadvantage to using 220V input?

thanks for any insight you can provide.

 

[markba633csi]

220 volts is definitely preferred since the input current to the vfd is reduced by half
There is some risk of overheating the motor when running at very low speed for extended periods
as the cooling is less than optimum
Pulley reduction has it's advantages since you get both speed reduction and torque multiplication
You lose torque with a VFD and motor combo so that's why the motor must be oversized

 

[yota]

220 volts is definitely preferred since the input current to the vfd is reduced by half
There is some risk of overheating the motor when running at very low speed for extended periods
as the cooling is less than optimum

thanks. I have read of people adding small fans to mitigate this. is overheating less with 115V input or is the overheating because of trying to go slow with a 1.5HP motor. or is it the motor type?

 

[markba633csi]

It's because the slower motor speed slows its internal fan as well, so adding an external fan is a good approach
220 volts reduces the supply current to the VFD which is beneficial for your house wiring and breaker box, less voltage loss
in the supply wiring means more power delivered to the VFD and to the motor

 

[mksj]

A TEFC motor that you have is probably good down to 20Hz and not over heat and also going below 20 Hz the although the motor torque remains the same the mechanical advantage is reduced by 1/3 vs. changing the belt ration and running the motor at 60Hz. By over sizing the motor, you somewhat compensate for this, and that is one of the reasons for up sizing the motor. The workload on the motor will also be reduced. A 4 pole motor run off a VFD usually can be run up to 120 Hz in this type of application without significant loss of Hp. Torque does fall off above the motor base speed of 60 Hz but you gain the mechanical advantage so mostly a wash. You still may need a low speed and high speed pulley setting.

The other consideration is the size Hp/amps of the motor, there are very few VFD's that will run off 120VAC and output 230VAC for a 1.5 Hp motor, they use a voltage doubler. You also would need a minimum of a 20A 120V circuit, the manufacturer recommends 30A.

 

[yota]

not totally enclosed. does this help?

 

[yota]

well, crap. waited too long and they sold it.

 

[MikeInOr]

not totally enclosed. does this help?

View attachment 502221

That looks like a TEFC (Totally Enclosed Fan Cooled) motor to me. To bad you missed it. It would have done a good job if it mated to your drill press well.

I don't know about your shop but in my shop I might use my drill press for 3 hours on a rare occasion and not at all on most days. I would not worry about heat build up in a home shop setting, it is really a non issue.

 

[yota]

agreed, no marathon shop drilling sessions going on here. don't think I've ever been on the drill press continuously for hours. the mill, yes. thanks.