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34549Re: [mill_drill] Replacement motor for Enco RF-30

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  • CS Mo
    Nov 6, 2013
      I have a 3hp VFD on my mill - I bought it many years ago from Dealer's Electric for around $4-500. Despite Guenther's misguided assertions, it works great and allows me to control the spindle RPM from Mach which can be very handy. It also allows much simpler on/off/estop circuitry and, as I have it wired up, I can either control it with Mach, or I have a rotary switch which sets 30hz-75hz for manual control.

      I have a 4.0hp VFD on my lathe - I bought it fairly recently from eBay for $130(!). It is 1/3rd the size of the VFD on my mill and has a relatively slow ramp up time..The VFD on the mill goes from off to 60hz in about a 10th of a second, the lathe VFD takes about 2 seconds. For the price differential, I can live with the slower ramp time. (As configured, out of the box, the ramp time was so slow it wouldn't actually turn the motor - 2 seconds is as fast as I've been able to get it to go after spending quite a bit of time configuring it.)

      Since my lathe requires the spindle to be stopped to change speeds, I find the VFD invaluable for changing speeds on-the-fly when turning multi-stepped pieces.

      If you do buy an cheap import VFD from eBay, or elsewhere, I'd buy one that is 50-100% larger than the motor you want to use it with. So, for a 1hp motor, I'd look for a 2hp VFD..etc.

      Also, if you're running a VFD from single phase, over 3hp, you want to de-rate the VFD by 33-50%. So, a 5hp VFD powered from single phase should only run a 3hp motor.

      Keep in mind that if you retrofit a machine with a VFD, you have to make sure that any mechanical switches do NOT switch AFTER the VFD.

      So, for example if your machine has a mechanical on-off switch, you need to wire it like so:


      You do not want:


      Or you'll have all sorts of problems.


      >I replaced my original motor with a VFD and am very happy with it although
      >it took awhile for the sting of the cost to subside. Here are the details:
      >I do have a second option that will be much lower cost and solves the odd
      >ball pulley bore problem. I will sell you my original motor for a reasonable
      >-----Original Message-----
      >From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On
      >Behalf Of Steve M
      >Sent: Wednesday, November 06, 2013 6:58 AM
      >To: mill_drill@yahoogroups.com
      >Subject: [mill_drill] Replacement motor for Enco RF-30
      >I bought an Enco branded RF-30 style mill from the original owner. Motor has
      >a manufacture date of 1987. Machine is in great condition minus the burned
      >up motor. I'm having a time of it trying to sort out what frame/mount would
      >be best for a replacement. I understand I'll have to address the odd ball
      >pulley bore when I get to that part of this.
      >Was thinking I'd like a good quality 2HP 3 phase motor for use with a VFD.
      >Any input much appreciated. I've searched all over the place with little
      >specifics coming up.
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