1
\$\begingroup\$

I am currently having an issue with an induction motor driving a conveyor belt too fast. It the connected to a Frequency inverter which is connected to a plc. The inverter is sat to output 50 hz. But i need it to run in 4 hz or less.

Would it do any harm running it so low? Anything i should be aware of before i change it?

This is the ratings on the Motor :

enter image description here

\$\endgroup\$
1
  • \$\begingroup\$ You'll burn out the motor at low RPM and 5x the rated current if full voltage , get a big pulley set or suitable chain reduction \$\endgroup\$ – Tony Stewart EE75 Nov 24 '16 at 20:28
1
\$\begingroup\$

A current design inverter designed to control the speed of an induction motor will be able to operate the motor at rated torque at nearly zero speed. The problem will be keeping the motor from overheating without the motion of the rotor moving air though and over the motor. You can operate the conveyor very briefly at the speed you want, but not continuously.

If the motor makes a lot of noise, the inverter may not be adjusted properly, but some additional noise is normal. You can check the current, but many ammeters will not work properly with the inverter waveform and frequency. The inverter may have a motor current display. The inverter manual should help with getting it running properly.

\$\endgroup\$
2
  • \$\begingroup\$ I will be turning it on and off.. It will not run continously \$\endgroup\$ – Carlton Banks Nov 24 '16 at 20:01
  • \$\begingroup\$ With a short enough duty cycle, you should be able to operate ok. \$\endgroup\$ – Charles Cowie Nov 24 '16 at 20:06
1
\$\begingroup\$

An induction motor is a bit like a transformer, drop the frequency, and you have to drop the voltage, or it will saturate and draw damaging current. Running the motor at <10% of its rated voltage, you'd be unlikely to get anything like adequate torque from it.

\$\endgroup\$
3
  • \$\begingroup\$ ...Yeah i thought something like that would be the case... The frecuency converter which it is connected to, make it move around 2.5 hz, but it makes a lot noise.. I need the motor to be barely moving. But i guess motors like these aren't made for barely moving?... \$\endgroup\$ – Carlton Banks Nov 24 '16 at 19:58
  • \$\begingroup\$ It's not a bit of a transformer, it is a transformer. There are induction motors out there with rotor coils and collector ring contacts. When you stop them mechanically you have a transformer with selectable phase shift. \$\endgroup\$ – Janka Nov 24 '16 at 23:36
  • \$\begingroup\$ @Carlton Banks: "Barely moving" is a problem for any motor because the reactance of the coils is connected to frequency. And they are usually rated for rather "high" frequencies as 50Hz. It's even true for a DC motor, though that one creates the AC needed to run it itself through the commutator. For continous running at low speeds, you always need a heavily overdimensioned rotor coil – or a gear. \$\endgroup\$ – Janka Nov 24 '16 at 23:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.