Ok, so it's just a REAL little thing on my PM-1228 lathe...

[woodchucker]

I can't actually tell you what the facts are concerning the motor in my machine. The label on the motor itself doesn't say AC or DC, and obviously the manual would be of no help since I don't know what "version" of the 1228 it is referencing.

You have an 1100 watt DC brushless servomotor.

how did you tell that? I was thinking it was a 3phase 230volt ac motor. Was it because of the "CONTROL SUPPLY"?

 

[verbotenwhisky]

I can't actually tell you what the facts are concerning the motor in my machine. The label on the motor itself doesn't say AC or DC, and obviously the manual would be of no help since I don't know what "version" of the 1228 it is referencing.

I went and looked, that unit does come with a DC motor, it just surprised me, please forgive for my reaction. When I bought my lathe I purposefully made certain it was an AC motor, they have more torque at lower RPM.

 

[mksj]

The motor is a BLDC, they have maximum torque at 0 speed, most 3 phase motors the torque falls off at lower speeds. It is also a factor of the mechanical drive ratio.

 

[woodchucker]

I went and looked, that unit does come with a DC motor, it just surprised me, please forgive for my reaction. When I bought my lathe I purposefully made certain it was an AC motor, they have more torque at lower RPM.

I thought DC had more torque at low rpm than AC.

 

[Dabbler]

1. there is no reason to describe polarity for a 3PH motor - and the line supply is found centre bottom.
2. 3500 rpm (nominal) is unusual for 3ph motors, but common top end for servo motors.
3. on the left side, not there are only 2 connections to the motor, not 3.

- it is a very safe bet this is a PWM DC motor, which means you will get bugger all torque at slow speeds. So DC Servo, or PWM DC motor, your choice.

 

[verbotenwhisky]

I thought DC had more torque at low rpm than AC.

In most cases, if you get the RPM up they are relatively comparable; but, at lower RPM the AC motor has more guts. NOW, does that apply to all? Not certain and I know there are those who disagree with me so all I can tell you is what my personal research found, I bought a lathe with an AC motor.

 

[Dabbler]

In most cases, if you get the RPM up they are relatively comparable; but, at lower RPM the AC motor has more guts. NOW, does that apply to all? Not certain and I know there are those who disagree with me so all I can tell you is what my personal research found, I bought a lathe with an AC motor.

Like just about everything, it depends. the high torque on a monarch 10ee is *because* of the DC motor... It depends on how the motor is wound, and how you supply current to it. If you are using a DC stepper motor, the torque is substantial at vey low speeds, and very little at max RPM. An AC motor torque drops off as slip increases - even with a boost in current. So when using a VFD, the torque falls off somewhat at slower speeds - in my experience about 1/3 is lost at speeds below 20 Hz..

 

[verbotenwhisky]

Like just about everything, it depends. the high torque on a monarch 10ee is *because* of the DC motor... It depends on how the motor is wound, and how you supply current to it. If you are using a DC stepper motor, the torque is substantial at vey low speeds, and very little at max RPM. An AC motor torque drops off as slip increases - even with a boost in current. So when using a VFD, the torque falls off somewhat at slower speeds - in my experience about 1/3 is lost at speeds below 20 Hz..

Hey Dabbler, I am not a sparky, I am more mechanical, Your comments on the AC fall in line with what I have researched, I knew there were better DC motors but made some assumptions based on cost. I did not realize that there were 3 Phase DC motors although I guess it makes sense that there would be. As I previously stated I did some research before I bought the lathe I have and although there were a number of reasons I chose the one I have the AC motor was part of it.

 

[verbotenwhisky]

Like just about everything, it depends. the high torque on a monarch 10ee is *because* of the DC motor... It depends on how the motor is wound, and how you supply current to it. If you are using a DC stepper motor, the torque is substantial at vey low speeds, and very little at max RPM. An AC motor torque drops off as slip increases - even with a boost in current. So when using a VFD, the torque falls off somewhat at slower speeds - in my experience about 1/3 is lost at speeds below 20 Hz..

Ran across the article which is pretty good for any that are interested, it supports Dabbler's comment: https://www.controleng.com/articles...of-pwm-when-controlling-a-brushless-dc-motor/

 

[Tired&Retired]

You have an 1100 watt DC brushless servomotor.

If that label were missing, is there any easy way to verify that?