How low can you go.

It depends on the type of motor, a TENV and TEBC are rated down to 0 speed, a TEFC which is the usual style of mill motor, around 15 Hz for any length of time. Below that point there is a higher chance of insufficient cooling. Depends a lot on the motor design, mass, type of load, duration, ambient temperature, etc. Since you loose Hp in a linear fashion below your base speed and you loose the mechanical advantage, turning down the VFD below 20 Hz you are operating with a significant reduction in power. So OK for light tapping/drilling, but less ideal if you are hogging out a lot pf metal.

Inverter/vector TENV motors and some TEFC motors often have temperature sensors in the motor that can be wired into the VFD to shut down if the motor overheats. A TENV typically barely gets warm at any speed, installed in manual mills and lathes.

Motor Temperature vs. freqiency.jpg
 
Permanent magnet AC motors will happily do zero speed. Word of warning: many vfd's DO NOT like these motors!!! They act rather differently from squirrel cage! If you are asking for.much.torque you should add an external fan for really low speed operation.

Sent from my SM-G892A using Tapatalk
 
Thank you everyone. I think I am happy with all the responses. I am posting pics of the motor and vfd specifications for interest sake,both are brand new.
20210517_113404.jpg

20210517_113638.jpg


Thanks guys
Michael
 
I read that your motor is 400v so in our world i would think that it is 380v. but most motors or many motors have the ability to be wired from star to delta. Your vfd is not clear in its output. At least i havent picked it up. Is it asingle phase 240v in 3ph 380v out or is it 240v in and 240v out. ? I see most bigger vendors in S Africa dont seem to supply the 3ph 380v out version.
 
plunger said:
I read that your motor is 400v so in our world i would think that it is 380v. but most motors or many motors have the ability to be wired from star to delta. Your vfd is not clear in its output. At least i havent picked it up. Is it asingle phase 240v in 3ph 380v out or is it 240v in and 240v out. ? I see most bigger vendors in S Africa dont seem to supply the 3ph 380v out version.
Click to expand...
I read the VFD nameplate as saying the output can be up to but not over the input voltage. So with 240V in, you can get no more than 240V out. As a former VFD design engineer, this is consistent with my experience. The circuitry inside a VFD can only reduce the voltage, unless they add a special "voltage doubler" input circuit. Traditionally this is only done for products that are intended to run on 120V single phase (mostly in the USA) and produce up to 240V output. Not saying someone couldn't put a voltage doubling front-end on a 240V single phase drive so that it could make 400 (or even 480) volts out. But I've never seen one.
 
You can get 240v single phase in to 380v three phase out vfds.
 
plunger said:
I read that your motor is 400v so in our world i would think that it is 380v. but most motors or many motors have the ability to be wired from star to delta. Your vfd is not clear in its output. At least i havent picked it up. Is it asingle phase 240v in 3ph 380v out or is it 240v in and 240v out. ? I see most bigger vendors in S Africa dont seem to supply the 3ph 380v out version.
Click to expand...
It's single phase 220V in and 380V three phase out. The motor is configured in Delta.
 
There is an outfit in the UK the sells step-up VFD's, that are 240V single phase in and 415V 3 phase out. Tend to be expensive, I have also seen some through Aliexpress, but do not know how well they work. The Alpha-Drive Micro VFD-A-E6-20022 above states that the voltage in (240V) = voltage out, so it will not output 380VAC 3 phase.

Drives Direct - Digital Phase Converters - Home Page

www.drivesdirect.co.uk
 
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