DC Motors

[SLM]

Going DC seems like a lot of trouble for not much benefit over a 3 phase AC with VFD.
I have never found it necessary to have the ability for small changes in speed for a drill.
Because of torque limitations at low frequency and motor specs at the high end - I usually only run VFD between 25 and 80 Hz
And yes, DC will be noisier.

Well I have 4 Meddings drills to mess about with, so it’s as much an experiment as a search for the easiest or best solution.

 

[Spectric]

Going DC seems like a lot of trouble for not much benefit over a 3 phase AC with VFD.

Having worked in many engineering firms the speed of the drills was not something that got changed that often, if a large morse taper drill was being used then the speed would be reduced by just moving the belt which was not time consuming but most of the time nothing was changed. My current drill is a very old Ajax and essentially I only drop the speed right down when using large flycutters otherwise it remains a fair bit higher. I always like to keep things simple and uncomplicated as you get less issues and more time to do what you want to.

 

[gcusick]

I’ve been toying with a similar idea, having read about some lathe conversions to brushless dc motors on one of the model engineering forums. There are some kits comprising a brushless motor and 230V controller, intended for industrial sewing machines. There are versions rated at 550 and 750W, with a 20:1 speed range (~200-4000rpm) that look as if they would fit the bill.

I’d be interested in any experience with these.

 

[pe2dave]

See if this helps:

This guy has lots on calculating motor needed for given speed / torque, excellent channel.
Also explains different types of motors.

 

[MorrisWoodman12]

I've mended a couple of wood lathe motor controllers, not that I have a lathe, and was a little surprised to find they were a DC motor. It's wired directly into a bridge rectified and the speed control is a phase controller so the motor is fed with larger or smaller chunks of the ac waveform. Can't remember what the power ratings were now so not sure if that technique is good enough for a drill press motor.
Have fun
Martin

 

[Myfordman]

I've mended a couple of wood lathe motor controllers, not that I have a lathe, and was a little surprised to find they were a DC motor. It's wired directly into a bridge rectified and the speed control is a phase controller so the motor is fed with larger or smaller chunks of the ac waveform. Can't remember what the power ratings were now so not sure if that technique is good enough for a drill press motor.
Have fun
Martin

They use a similar scheme on some toy milling machines and quite often see users having problems with the controllers.
I feel that if the OP wants to experiment with DC motors then fine but the sure fire easy way to get reversing and variable speed with good torque is a vector (or sensorless) inverter and a cheap 3 phase motor discarded by someone making the reverse conversion to single phase.

 

[SLM]

This guy has lots on calculating motor needed for given speed / torque, excellent channel.
Also explains different types of motors.

Great! Thanks for the link

 

[SLM]

They use a similar scheme on some toy milling machines and quite often see users having problems with the controllers.
I feel that if the OP wants to experiment with DC motors then fine but the sure fire easy way to get reversing and variable speed with good torque is a vector (or sensorless) inverter and a cheap 3 phase motor discarded by someone making the reverse conversion to single phase.

Yep, I think that’s agreed; it’s as much an itch to scratch, having seen commercially available drills (eg from Axminster), boasting a DC motor.

 

[Spectric]

Give this a read, Microchip make some very good products in this field and take a look at Brushless DC (BLDC) Motor Control | Microchip Technology

 

[SLM]

Give this a read, Microchip make some very good products in this field and take a look at Brushless DC (BLDC) Motor Control | Microchip Technology

Thank you! That looks an informative read