Picked up a new series1 Bridgeport, needing some help with wiring

Ltk · Dec 19, 2021

I have searched through some threads and did find some articles about running a 208v machine on 240v with some conflicting responses, but none that matched my specific problem.

The machines motor itself is wired 208v, the power-feed on the long axis of the table is a 208v Reliance motor. The previous owner had connected the leads from the drum switch to the power feed motor in the back of a 110v receptacle, I am not sure how they had wired the main power into this or if this is even a proper way to do it?

Black cable is going to the powerfeed, gray goes to the drum switch on the head. Any help would be greatly appreciated. Do I need to purchase a motor starter or just wire into this mess?

J_R_Thiele · Dec 19, 2021

Let me start with a question. In your post about the phase converter you say it is being fed 220V single phase. Here you are talking about 240 Volts. What do you find when you measure the actual voltage you have?

Motors should work with power with 10% of the nameplate voltage. 208 x 1.10 = 228.8. 208 x .9 = 187.2

If the voltage on your end of the meter is within 188 to 228 you should be OK by that standard.
Hopefully you are on the higher side of that variation, as a given guage of wire will carry more energy at a higher voltage.
Of course, there is no free lunch in this. The insulation needs to be adequate for the higher voltage.

Ltk · Dec 20, 2021

J_R_Thiele said:
Let me start with a question. In your post about the phase converter you say it is being fed 220V single phase. Here you are talking about 240 Volts. What do you find when you measure the actual voltage you have?

Sorry for the confusion, I am actually getting 231 volts from the single phase input. When the RPC is on and measuring on the 3 lugs in the 3-phase sub panel, I am getting 236v from Line 1 to 2, 230v from Line 1 to 3, and 237v from Line 2 to 3. Does this sound okay to run the 208v powerfeed motor pictured here? If so, do I just pigtail all 3 hot leads from the powerfeed motor into the machine input and machine motor connections?

neilho · Dec 20, 2021

Try it, see if it overheats. That's the danger in over voltage. And if it does overheat, buck/boost transformer(s) can bring the voltage down.

J_R_Thiele · Dec 20, 2021

I agree with neilho. Try it and see. The voltage you are getting is lower than I was anticipating.

With regards to wiring it up: I am reluctant to just say to go ahead based on a few pictures- which cannot show the whole system.
Some questions: Why are the wires in the box disconnected? Does the box actually have 120 v outlets? Looks like it does, and someone had red wire handy and used it for everything. That makes me wonder about everything else. I assume the power to the machine came into the box with the 3 power lines, a ground, and a neutral for the outlets to be powered of the 3 phase lines.

Try finding a copy of the factory manual in installation and see what they show.

Ltk · Dec 20, 2021

J_R_Thiele said:
.

I have been running it for a few hours today without the powerfeed or 110v outlets hooked up and everything is fine heat-wise. They have a 4 wire cord coming from the motor's drum switch, and a 3 wire cord coming from the powerfeed motor. They tied all 3 from the powerfeed into each of the 3 hot legs and the 110v outlet looks like it was jumped off of 1 hot leg, with no neutral anywhere that I can see. The 110v outlets aren't a big deal, I have one directly over the machine for use if the need arises.

I guess my concern is just tying the powerfeed motor into the input power along with the main motor power also. I've never pigtailed two motors into a 3 phase circuit, is this standard practice to wiring up a powerfeed motor or do I need a seperate breaker for that one all by itself?

J_R_Thiele · Dec 20, 2021

You are asking the right questions. If the ground was being used as a neutral- you do not want to be following their wiring examples...

You will sleep better if you get a small NEMA 1 box and in it have over load protection for both the motors.

If it is easy to run in a neutral you could do that and decide later if you actually want to wire in the single phase outlets. The 4 conductor + ground costs a little more than 3 conductor + ground, and not nearly as much as replacing 3 conductor in the future if you change your mind.

Ltk · Dec 21, 2021

J_R_Thiele said:
.

I went ahead and wired it up tying all 3 together. That is, input from 3 phase subpanel to Bridgeport main motor drum switch, powerfeed motor wired into that aswell. Correct rotation on everything and works flawlessly, the motors are both getting a little hotter than I believe they should, I haven't checked temps yet but they are not so hot that I cannot hold my hand on it.

Is there a line I should draw when it comes to the heat situation? I've spent an incredible amount of money already but if it were you, would you buy a buck/boost transformer? If so, do you happen to know where to source one and which particular one I need? Thanks!

J_R_Thiele · Dec 21, 2021

If this were mine, I would wire it up and use it, and keep an eye on the temperatures. The hand method works, but I would use one of my $69 Thermoworks IR gun Shop - Products - Infrareds - Page 1 - ThermoWorks That way I can record numbers and track over time if I feel the need.

The motors are rated for continuous duty at --full load-- but that is not how you or I would be using them. They will heat up when on- but that will be for a fairly short time, then they will be off again and start cooling down.

I do not have any relevant experience with buck/boost transformers. If you do go that route, factor the shipping into the cost due to the weight.

Ltk · Dec 21, 2021

Thank you for all of your advice again. I will purchase a nice IR thermometer and keep an eye on the temps. Yea once the new wears off I'd say this will only see 4-5 hours of use a week in short bursts. Any idea what temperature would be concerning? Might be cheaper to rewire the main motor for 230v and buy another powerfeed motor that is made for 230v, I'll study that when/if the time comes.

J_R_Thiele · Dec 21, 2021

Google has its uses.

Electric Motor Insulation Class - What is It?

https://www.thesnellgroup.com/featured-tips/understanding-insulation-class-temperature

The maximum winding temperature of class A insulation is 105 C. They cite rule of thumb that winding temperature is 30 C higher than surface temperature. If your motors surface temperature reaches 75 C you are having problems. That would be 167 F, so you will not be holding your hand on it.

FYI- none of the articles I looked at mentioned anything about insulation class and voltage- only temperature.

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