3 phase question

machinistnoob

machinistnoob

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Hello all. I'm looking for some clarification on some wiring. I know explaining wiring and electrical can be tricky but here it is. I got a new mill with a 3 phase motor and coolant pump. The previous owner was running a static converter. I will be using a rotary. The enclosure on the back is a square D brand, 3 phase disconnect. The picture shows how the previous owner has it wired. The three legs, seen on the top connection, are from the static converter. Just 3 wires. On the bottom right, you see the connections going out to the motor and pump. Each has 3 legs and a white wire going to a bus bar. Is that for ground/earth?
My rotary has the three legs and a ground/earth on the discharge side. Do I connect the ground/earth to the bus bar? Thanks in advance.
M. Noob
 

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If the orange cord was the input, it is wired poorly. You need 4 wires coming in, three for the 3 phase, plus ground. It looks to me like someone used a standard 120v extension cord (orange) to wire it and omitted ground. While I’m not known for being rigidly compliant with every wiring safety rule, not having a ground is quite dangerous (but functional).

The busbar with white wires would presumably be used for ground but without more info it isn’t clear. Some three phase equipment uses neutral to derive 120v for controls. By code and tradition, white is used for neutral and green for ground. So it is possible the bus bar could be a poorly color coded ground bus, or it could be a neutral bus.

Start by identifying the connection at the other end of those white wires on the bus bar. If it is wired to a case/frame screw, then they are being used as a ground. If it is wired to any active component it is being used as a neutral. I suspect it is an internal ground connection since it is not connected to the external cord, but you need to verify that for safety.
 
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Yep, that's what you need to do! Quick trip to the hardware store for some 4 conductor (like the black jacketed cables) and get a proper ground run!

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Using a green wire for a power wire deserves a trip to the principal's office
or having to stand in the corner with a dunce hat- very bad practice
At the very least, a piece of red tape on the wire should have been used to indicate a hot phase
 
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machinistnoob said:
Hello all. I'm looking for some clarification on some wiring. I know explaining wiring and electrical can be tricky but here it is. I got a new mill with a 3 phase motor and coolant pump. The previous owner was running a static converter. I will be using a rotary. The enclosure on the back is a square D brand, 3 phase disconnect. The picture shows how the previous owner has it wired. The three legs, seen on the top connection, are from the static converter. Just 3 wires. On the bottom right, you see the connections going out to the motor and pump. Each has 3 legs and a white wire going to a bus bar. Is that for ground/earth?
My rotary has the three legs and a ground/earth on the discharge side. Do I connect the ground/earth to the bus bar? Thanks in advance.
M. Noob
Click to expand...
More than likely those white wires coming from the motors are indeed ground. As suggested be certain to verify at the motor end. While you're at the store getting proper four (4) conductor wire, grab some green electrical tape so you can label them as such. Make sure the ground from the motors are tied to the (new) ground coming into the box. Make sure the (new) ground coming into the box is tied to the ground bar at the electrical panel. I would be suspicious of the motor wiring as well being clean and safe. Maybe consider offering your local electrician a six pack to give you a hand.
 
rabler said:
If the orange cord was the input, it is wired poorly. You need 4 wires coming in, three for the 3 phase, plus ground. It looks to me like someone used a standard 120v extension cord (orange) to wire it and omitted ground. While I’m not known for being rigidly compliant with every wiring safety rule, not having a ground is quite dangerous (but functional).

The busbar with white wires would presumably be used for ground but without more info it isn’t clear. Some three phase equipment uses neutral to derive 120v for controls. By code and tradition, white is used for neutral and green for ground. So it is possible the bus bar could be a poorly color coded ground bus, or it could be a neutral bus.

Start by identifying the connection at the other end of those white wires on the bus bar. If it is wired to a case/frame screw, then they are being used as a ground. If it is wired to any active component it is being used as a neutral. I suspect it is an internal ground connection since it is not connected to the external cord, but you need to verify that for safety.
Click to expand...
Copy that. I'll trace out the white to the switches and motors. Should have done that first. I have been into the coolant pump and it has a fourth wire bonded to the box, but it's a yellow wire. I'll check the switches and report back. Thanks!
M. Noob
 
rabler said:
If the orange cord was the input, it is wired poorly. You need 4 wires coming in, three for the 3 phase, plus ground. It looks to me like someone used a standard 120v extension cord (orange) to wire it and omitted ground. While I’m not known for being rigidly compliant with every wiring safety rule, not having a ground is quite dangerous (but functional).

The busbar with white wires would presumably be used for ground but without more info it isn’t clear. Some three phase equipment uses neutral to derive 120v for controls. By code and tradition, white is used for neutral and green for ground. So it is possible the bus bar could be a poorly color coded ground bus, or it could be a neutral bus.

Start by identifying the connection at the other end of those white wires on the bus bar. If it is wired to a case/frame screw, then they are being used as a ground. If it is wired to any active component it is being used as a neutral. I suspect it is an internal ground connection since it is not connected to the external cord, but you need to verify that for safety.
Click to expand...
Also, if the white wires turn out to be ground, do I bond to the bar with the hook up, or just to the box? Thanks again.
 
Replace the 3 wire with input wire with 12/4 SOOW or equivalent cord.
The Red, White, and Black are for the 3 phase load, the Green is solely used for grounding purposes.
Most industrial applications will use a Blue wire for the 3rd load wire instead of a White wire. I have also seen White and Black wires wrapped with Blue tag tape to identify the 3rd phase

Directional control is determined by wire sequence. By swapping any 2 of the 3 load wires, the motor direction will reverse when sufficient power is applied.
 
I would remove the existing wires get the correct 4 color code wiring and rewire it correctly. Get something wrong and it could be serious, it is not only for your own safety but for others. Assuming it is 3 phase power from the RPC and you are driving a 3 Hp motor, you can run 12 or 14 AWG depending on the size of the RPC and if it has a breaker/fusing. There should be no neutral unless you are breaking out 120VAC and then that would need separate breaker/fusing. The power drives and DRO are most likely 120VAC single phase. If there is a transformer, in the control system only the ungenerated legs should be connected to it.

3 phase wire with ground.

If you use SOOW type wire with a white wire that is carrying current, then you should put some electrical tape (I usually use blue or black) at either end to denote that is not a neutral.

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Ulma Doctor said:
Replace the 3 wire with input wire with 12/4 SOOW or equivalent cord.
The Red, White, and Black are for the 3 phase load, the Green is solely used for grounding purposes.
Most industrial applications will use a Blue wire for the 3rd load wire instead of a White wire. I have also seen White and Black wires wrapped with Blue tag tape to identify the 3rd phase

Directional control is determined by wire sequence. By swapping any 2 of the 3 load wires, the motor direction will reverse when sufficient power is applied.
Click to expand...
Yes. That was happening anyway. I have the proper cable. Photo is just to show the current setup. Thank you for your help.
M. Noob
 
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