3ph delta star switch, delta tripping fuse

[D Skelton]

Another tip,when installing a machine which you are unfamiliar with,make sure phase sequence is correct at the machines incoming terminals then get someone who knows how to operate it to start it up,that way there's no chance of being blamed for any damage caused by operator error.Yes we know how to connect machines up but operating them can be expensive if we don't know how to do it correctly.

Straight out of the University of Life that one! And their course; C&G 2397 - Certificate in the employment of passing the buck techniques.

 

[Knobhead]

You'd have thought the bump tests non loaded would be second nature to an electrician?! I had this drilled into me over and over again when I was an apprentice! "Bump in star, check rotation!", "bump in delta, check rotation again!".

The trouble is, it's quicker to take shortcuts.

 

[D Skelton]

The trouble is, it's quicker to take shortcuts.

What? Like "wire it up, hope for the best and scarper before someone else turns it on!". Lol!

 

[Deleted member 72666]

I still think this is a 'home made ' jobbie! I also fear that it doesn't have the basic safety features we take for granted found in control cct's. such as 'overload' and 'no volt' protection, electrical and mechanical interlocks, etc the list goes on!
I once worked on a single phase planer that was built in Slovenia, It's control panel consisted of an on/off switch, forward/ reverse switch and thermal o/l unit and nothing else!

 

[Lucien Nunes]

OP: You should be able to switch to delta as soon as the motor is nearly up to speed. A circular saw starts unloaded so the starting duty isn't very demanding, apart from the inertia of the blade. If you have to wait longer before switching, without the motor speed increasing, then there is a fault. Check the current in each of the three lines when running in delta to confirm that all three phases are functioning correctly - they should all be very similar. An oversized motor can sometimes carry on running with a supply phase out, although it will eventually overheat, especially if you don't have proper overload protection.

However, more than anything else, I would say that in these enlightened times running a circular saw without no-volt release is unacceptably dangerous. Never mind the fine details of electrical safety, the possible consequences of a sawbench starting up without warning are serious!

 

[D Skelton]

running a circular saw without no-volt release is unacceptably dangerous. Never mind the fine details of electrical safety, the possible consequences of a sawbench starting up without warning are serious!

Forgive me if I'm being a bit blind but I can't see anywhere where the OP has indicated that there isn't a no-volt release. It's running via a standard YD starter.

 

[Deleted member 72666]

As I understand it he's using a multi-pole swich to do the changeover, thus not using contactors.

 

[D Skelton]

As I understand it he's using a multi-pole swich to do the changeover, thus not using contactors.

I must have missed that post. Oops.

 

[T0RN4D0]

The whole unit was home made. Regulations are not a problem because there basically are none when it comes to what you're using at home. And yes, there is no no-volt release and no motor protection. I think it might be worth adding it.


I didn't check the current on all phases, would be easy enough to do. Did check the voltage on all three phases (only had a DMM with me) on the motor clamps and that was fine, but i guess that doesn't matter if there's a problem with one of the windings.

Is it possible that the breaker is so close to the limit when starting it needs a few seconds to "cool off" before its able to go through another over-amp jolt when switching to delta?

 

[Deleted member 72666]

Deleted.

 

[D Skelton]

Jeez, this saw sounds like a death trap! No no-volt protection, no OL protection, manual changeover without interlock, not rotation tested before running!

Run away!

 

[T0RN4D0]

Circular saws are death traps if you don't use them carefully. And no amount of protection (especially OL) can help you there.

 

[Deleted member 72666]

The whole unit was home made. Regulations are not a problem because there basically are none when it comes to what you're using at home. And yes, there is no no-volt release and no motor protection. I think it might be worth adding it.


I didn't check the current on all phases, would be easy enough to do. Did check the voltage on all three phases (only had a DMM with me) on the motor clamps and that was fine, but i guess that doesn't matter if there's a problem with one of the windings.

Is it possible that the breaker is so close to the limit when starting it needs a few seconds to "cool off" before its able to go through another over-amp jolt when switching to delta?

I suspected as much (see post #24). But my advise to you would be: do the right thing, either scrap this monstrosity altogether or spend a little time and money and make this right with ALL the safety features in place.
As for the motor check and compare between windings for resistance and windings to earth for leakage.