Advice on VFD and other electrical questions get a Delta Rockwell 34-395 saw running

[James Goodman]

I’m a recently retired carpenter / builder and I’m in the process of setting up my workshop. Years ago a bought a Delta Rockwell 34-395 12”/14” table saw that was not running and was in a state of partial disassembly. I have never seen it run had it running. I want to set it up as a dedicated rip saw with a stock feeder (as yet unpurchased). I have a 3-car, freestanding garage with a 1-bedroom apartment over it on my property and I’m going to use the 3-car garage as my workshop. I have 200-amp, 1-phase service in the building and it’s on its own meter. The guy I bought the property from had set up the garage nicely with lots of receptacles at workbench height around the perimeter walls on several 20-amp circuits I also have 2 receptacles on the ceiling for 2 overhead garage door openings and 8 other switched receptacles on the ceiling for shop lights, My current significant power draws in the building are an electric dryer circuit, a heat pump to heat and cool the apartment, and an electric water heater. So, there’s a good amount of room still in the panel for additional loads.

Before I get into some details, I want to say that while I’ve done some wiring, in the course of building houses, and have wired a couple of my own houses, it was all basic stuff. I’ve never connected high-voltage equipment and never wired machine controls of any kind. The biggest point I want to mention is that while I can do some wiring, I do not fully understand electricity. I’m fine with 120 volts, but 208 and up, and 3-phase are way out of my comfort zone. I’m So, I can follow instructions, but when we start getting into more advanced electrical ‘jargon’ and terminology, there’s a good chance I won’t know what you’re talking about if you can’t dumb it down to the 1^st-grader level that my pea-sized brain can handle. My intention is to run all the conduit and conductors and have an electrician in to do the panel connections and machine controls connections.

The motor on the saw is not the original and it looks pretty new. It’s 5hp, 3 phase. I’ve attached a photo of the motor plate and photos of the saw. When I bought the saw, it had the following items mounted to the pedestal.
· A fused disconnect with 3 fuses and throw-handle to open and close the circuit.
· A magnetic starter that did NOT have an integral on/off switch
· A separate push-button on/off switch that was connected to the magnetic starter via a 3-conductor-plus-ground cable.

QUESTIONS:
I briefly considered getting a RPC, but I might end up with just one more 3-phase machine (band saw) so I want to go the VFD route. Here is my first set of questions about the VFD:
1. When using a VFD, do you still have a magnetic starter?
a. If you do still need a magnetic starter, can they be had with integral on /off buttons or do you need a separate starter and separate on/off switch like the saw had when I bought it?
2. When using a VFD, if you do not need a magnetic starter, do you still need an on/off switch? In looking at photos of VFDs, the buttons look quite small and I’m concerned from a safety standpoint, that if you don’t need an on/off switch, that the kill button on the VFD will be hard to find.
3. Since the machine will be fed with single phase power, and the VFD is converting it to 3-phase, is the amperage draw of the motor still the same as if it were being powered by native 3-phase power or is there a loss of power with the conversion?
4. I have read in other forums that the VFD should be rated at 2X the horsepower of the motor. So, following that recommendation, I’d be looking for a 10 hp VFD. Is this correct? Do you need a VFD rated at twice the horsepower of the motor that it’s running?
5. I don’t want to spend a gazillion dollars on this project but I’m also not sure I should buy a VFD from Amazon. I have looked at Automation Direct https://www.automationdirect.com/adc...20desc&start=0
and they have the following 2 categories of drives on their website:
· General Purpose AC Drives
o Several speed control modes available: standard V/Hz with pulse input feedback, sensorless vector control (SVC), and ultra precise Field Oriented Vector control (FOC).
· High-Performance AC Drives
o Closed-loop flux vector and torque control modes available in sizes up to 60 hp
I’m guessing that since this isn’t a CNC machine we’re talking about, the ‘General Purpose AC Drive’ is all I need, is that correct?
6. I am putting the saw on casters and need to be able to roll it out of the way. Can I use flexible cord with twist-lock connector to connect the VFD to power?

Thanks for taking the time to read this

[Marc Fenneuff]

1. No mag starter, the VFD replaces that function.

2. You can use the VFD control panel as the on/off control, but it’s easier to wire a momentary switch for that purpose.

3. Amps are amps. You configure the VFD to provide, at maximum, the full load amps the motor is capable of drawing.

4. That is incorrect, you should size the VFD for the HP of the motor.

5. I highly recommend Automation Direct. They are not the cheapest but they will help you select the correct VFD for your application.

6. Yes you can

[James Goodman]

1. No mag starter, the VFD replaces that function.

2. You can use the VFD control panel as the on/off control, but it’s easier to wire a momentary switch for that purpose.

3. Amps are amps. You configure the VFD to provide, at maximum, the full load amps the motor is capable of drawing.

4. That is incorrect, you should size the VFD for the HP of the motor.

5. I highly recommend Automation Direct. They are not the cheapest but they will help you select the correct VFD for your application.

6. Yes you can

Thanks very much. Is the wiring of the momentary switch straightforward? Would instructions to do so be part of the instructions for the VFD?

[James Goodman]

One other question: When the VFD is configured, do you have to account for inrush amps when the motor is starting or just regular full load amps? Thanks

[Dan Friedrichs]

You program the VFD with the full-load amps.

The momentary switches are very straightforward - usually 3 wires for start and stop as shown here: https://www.hobby-machinist.com/data...b3ef6198ce.jpg

[James Goodman]

You program the VFD with the full-load amps.

The momentary switches are very straightforward - usually 3 wires for start and stop as shown here: https://www.hobby-machinist.com/data...b3ef6198ce.jpg

Thank you and thanks for the diagram.

[Ron Selzer]

One other question: When the VFD is configured, do you have to account for inrush amps when the motor is starting or just regular full load amps? Thanks

Regular full load amps, IF the VFD is programed correctly (probably factory settings) then it will ramp the motor up to speed instead of drawing high inrush until at speed. One of the major benefits of using a VFD.

adding: Definitely get rid of the motor starter and disconnect switch already on saw, rewire the on/off pushbutton to the vfd as shown in the diagram given already to you. Use a flexible cord sized properly to power the VFD, recommend twist lock cord ends however straight cord ends work well also.

I have a 3 phase band saw, 2 hp motor with a VFD, works great, need to wire a push button start/stop switch to vfd as those little buttons are hard to use. Originally planed on using a rotary phase converter, however took so long to get the panel for it, that I bought a cheap vfd from Amazon to temporarily run the band saw. Like how easy it starts and when the rotary phase converter panel showed up 6 months later have no desire to use it.

Ron

[James Goodman]

Regular full load amps, IF the VFD is programed correctly (probably factory settings) then it will ramp the motor up to speed instead of drawing high inrush until at speed. One of the major benefits of using a VFD.

adding: Definitely get rid of the motor starter and disconnect switch already on saw, rewire the on/off pushbutton to the vfd as shown in the diagram given already to you. Use a flexible cord sized properly to power the VFD, recommend twist lock cord ends however straight cord ends work well also.

I have a 3 phase band saw, 2 hp motor with a VFD, works great, need to wire a push button start/stop switch to vfd as those little buttons are hard to use. Originally planed on using a rotary phase converter, however took so long to get the panel for it, that I bought a cheap vfd from Amazon to temporarily run the band saw. Like how easy it starts and when the rotary phase converter panel showed up 6 months later have no desire to use it.

Ron

Thanks for that info and advice!

[Bill Dufour]

General recommendation is set acceleration to 3 seconds or more. Same for deceleration. Any faster can unscrew blade nuts etc.
Lock out reverse on the VFD.
For a saw you do not need speed/frequency control. Set min/max frequency to 60 hz.
Their is a parameter that needs to be changed to enable remote switches. Until that happens all control is from the panel only
Bill D

[James Goodman]

General recommendation is set acceleration to 3 seconds or more. Same for deceleration. Any faster can unscrew blade nuts etc.
Lock out reverse on the VFD.
For a saw you do not need speed/frequency control. Set min/max frequency to 60 hz.
Their is a parameter that needs to be changed to enable remote switches. Until that happens all control is from the panel only
Bill D

Thanks, Bill.

[Rod Sheridan]

In addition to the good advice given above, keep a disconnect switch on the saw wired to the input of the VFD.

It greatly improves your safety when making adjustments or blade changes…..Regards, Rod

[John K Jordan]

Thank you and thanks for the diagram.

Check the wiring diagram that should be in the manual for the VFD you get. Some use a SPDT or SPST switch for on/off instead of momentary contact switches.

[Jared Sankovich]

4. That is incorrect, you should size the VFD for the HP of the motor.

That's only correct on a single phase input rated vfd. If it's a 3p input vfd you need to de-rate.

[James Goodman]

In addition to the good advice given above, keep a disconnect switch on the saw wired to the input of the VFD.

It greatly improves your safety when making adjustments or blade changes…..Regards, Rod

Thank you Rod, yes I was going to continue to include a disconnect.

[James Goodman]

That's only correct on a single phase input rated vfd. If it's a 3p input vfd you need to de-rate.

Oh I see! Thank you for that distinction! It is a single phase input, so in that case, it sounds like you are confirming what Marc Fenneuff said.....that I match the hp of the VFD to the hp of the motor, is that correct? I will also confirm with Automation Direct from whom I will be buying the VFD.