Let me start by saying pardon my ignorance on the topic. I have knowledge in electrical wiring but not so much in the technical engineering aspects of motors and micro-controllers.

I just purchased a Lincoln conveyor oven for a startup I'm working on. (They're are no electronics on the motor). The oven has a conveyor that has a slow and fast speed. I want to put a speed control on the motor to achieve a conveyor speed in between the two factory speeds. Basically set the motor to high and then have a separate control to slow down the motor (Not looking to double or triple motor speed).

This is the specs on the motor:

Brother Motor

6 Wire harness to motor

Gry | Red | Blk
Brn | Wht | Wht

I've been digging around the internet but I wan't to make sure I'm doing this in the way that will ensure the full life of the equipment. I know voltage control is not a good method with a 3 phase motor. Any suggestion on how I could achieve the preferable with some type of rotary pot switch for granular control over the speed and no electronics.

Any help is greatly appreciated.


closed as off-topic by Chris Stratton, uint128_t, Voltage Spike, Daniel Grillo, brhans Jan 9 '17 at 22:05

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Chris Stratton, uint128_t, Voltage Spike, Daniel Grillo, brhans
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  • 1
    \$\begingroup\$ That is a single phase motor with either a start or run capacitor, not a 3 phase motor. In theory some severe software change of a typical 3-phase VFD might be able to run it (ie, drive its main and start winding without the capacitor), but you are probably better off swapping out the motor. Unless you plan to try to engineer a motor drive from scratch, this question isn't really on topic here. \$\endgroup\$ – Chris Stratton Jan 2 '17 at 0:40
  • \$\begingroup\$ @ChrisStratton Hi Chris thanks for the reply but can you clarify a little bit for me ? If it's a one phase moter can't I just put a potentiometer on the hot leg to lower the voltage and then slow the motor speed or is here something I'm missing ? \$\endgroup\$ – bumble_bee_tuna Jan 2 '17 at 0:52
  • \$\begingroup\$ No, induction motors really aren't designed for that. Electronic speed control of 3 phase ones is done by synthesizing an AC waveform at a custom line frequency, but your motor doesn't support that. You will probably need to replace it with a different motor type or add mechanical reduction (it looks like it's probably a 1725 RPM motor with 50x reduction already). This isn't really the forum for practical advice on any of those issues... you are more in garage/farm mechanic territory. Something like roller chain might work, but you'd need shielding, to fabricate a new mount, etc. \$\endgroup\$ – Chris Stratton Jan 2 '17 at 0:54
  • \$\begingroup\$ @ChrisStratton I'm sorry for posting in the wrong forum could you point me in the direction of a forum that would help me solve this problem. Also by mechanical reduction would that involve change the gear set going from the motor to the drive shaft ? Is that a possible fix ? \$\endgroup\$ – bumble_bee_tuna Jan 2 '17 at 1:07
  • 1
    \$\begingroup\$ If all you need is a single speed that is between the two speeds you have, the best thing to do is to change the ratio between the motor and the final driven shaft. The simplest and least expensive method would be to change or insert a ratio between the output of the gear you have and the conveyor drive shaft. You could also buy a new motor/gearhead (gear motor) assembly similar to the one you have. \$\endgroup\$ – Charles Cowie Jan 2 '17 at 2:34

There are commercial units that will do your speed control task very well. They allow you to increase and decrease speed of the motor. Typically they are VFD (variable frequency drives) that can alter both voltage and frequency. Here are some great ones I've seen used in production environments, though not cheap.

If you have the skills you can hack together speed control of PFC motors, but only within a small range. If you are looking to drop the speed by only 10% or so then that may be possible using a Triac speed controller or a Zero Crossing SSR, but it's not for the feint of heart to implement. You can read this to get clues on how to implement.

The other technique I have seen used to lower the speed of PSC's is to do cycle dropping with an SSR. If you drop 1 cycle in 20, then 2 cycles in 20 and so on, your speed will drop. Range is typically limited to about -20%. You must be careful that the speed does not drop to the point where the Start capacitor switches back into circuit (if you have one).

  • \$\begingroup\$ I believe that Optidrive used to recommend against using the single-phase motor unit for constant-torque loads (ie conveyors). Now they say "Optidrive E2 single phase output can be used to provide energy efficient, accurate speed control of single phase motors in a variety of applications, especially fans and pumps which typically do not require high starting torque." I would also worry about overheating with such a small motor. However VFD will be better than voltage reduction. Any kind of voltage reduction will be much less likely to work acceptably for a conveyor rather than a fan or pump. \$\endgroup\$ – Charles Cowie Jan 2 '17 at 11:12

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