C&G 2391

[meerkat]

I am in the process of building a test rig for the 2391,

can anyone remember if the DOL circuit socket outlet was a 5 pin (3 phase+N+CPC)

or 4 pin (3 phase+CPC) cheers (MEERKAT)

 

[Sidewinder]

meerkat,

No I can't but, IIRC it is a DOL starter to power a motor?

Doubtful you'll need an N for a "normal" squirrel cage 3ph motor.

 

[meerkat]

thanks sidewinder,

the reason I ask is that the rig at my college is fitted with a 5 pin socket,

trying to understand why?

I appreciate that a normal 3 phase motor does not have a Neutral connection,

thanks for your help

(MEERKAT)

 

[Sidewinder]

OK, 5 pin TPNE could be used to power a motor with a separate cooling fan which was 1ph (bad design!) or a 1ph brake (again bad design!)

There could be reasons for a 5pin but IMHO not connected to a 3pole DOL starter I can think of at the moment.

Sorry can't be more help, bad day.

 

[meerkat]

cheers sidewinder,

I think they had a spare 5 pin lying around or somebody ordered the wrong part,

just wanted to make sure I hadnt missed a trick somewhere,

thanks again (MEERKAT)

 

[Sidewinder]

Canoe, that's wrong though bud if it is there it should be connected!

Take this as a real install, a 5pin you would connect a TPNE load to which if the N is not connected could cause issues.

 

[meerkat]

cheers canoe,

just what I was thinking,

I know from experience that colleges sometimes use 1.5mm cable instead of 2.5mm cable because of a lack of resources,

so using a 5 pin with the neutral not connected fits the bill, but isnt technically correct and may send out the wrong message to certain students, cheers (MEERKAT)

 

[Brian 157]

It could be TP&N or TP. The C&G spec for the rigs shows a neutral going to the isolator but not to the socket, it also shows a 230v coil but many centres use a 400v coil. If the External Verifier from the Guilds has inspected & approved the rig then it's ok either way.

For Zs testing purposes it's better to have TP&N (for three lead testers) but you are allowed to calculate the Zs on this circuit.

 

[meerkat]

thanks brian, surely the dol starter requires a neutral at one side of the coil supply end, I thought this connection could be used aswell as a line connection and the cpc connection on the load side to measure Zs,

Zs can also be calculated using formula Zs = Ze+(R1+R2)

I would go for the calculated method, limiting the amount of live testing, and to obtain R1+R2 I would take the reading at the load side of the socket, holding the contactor in with a screwdriver, having linked out the Line and CPC in the DB.

(MEERKAT)

 

[Andy™]

thanks brian, surely the dol starter requires a neutral at one side of the coil supply end

you can get 400v coils. connect between 2 phases

 

[meerkat]

Hi Andy, thanks for the info, only ever connected a 230V coil, could you show me how this would be done using a simple diagram, not had much experience with 400V coils, cheers (MEERKAT)

 

[Sidewinder]

Meerkat,

400 V coils are common in simple balanced 3ph machines use 1 ph as live use the other as N simples!

 

[meerkat]

thanks Sidewinder, well I never new that, shows you how little I know.

I can honestly say, I have learnt so much from you guy's on this forum, far more than I ever did at college, keep up the good work, and thanks once again !!!!!

(MEERKAT)

 

[Andy™]

Hi Andy, thanks for the info, only ever connected a 230V coil, could you show me how this would be done using a simple diagram, not had much experience with 400V coils, cheers (MEERKAT)

swap the neutral to a another phase.....

you can also get coils in 110v, 24v, 12v and others

 

[philbas]

I can honestly say, I have learnt so much from you guy's on this forum, far more than I ever did at college, keep up the good work, and thanks once again !!!!!(MEERKAT)

I will second this, If I had relied on the information given by my course provider I would never have passed my exams, but following the threads on here gave me a real insight into how things work in the reall world.

My tip to anyone still learning (which is all of us )

Keep your copy of the regs handy (whatever colour it is at the moment) and when something comes up here open the book look at the regs quoted in the thread and form your own opinions on how they should be interpreted.

 

[meerkat]

thanks Andy, Philbas, for sharing the knowledge, appreciate it

(MEERKAT)

 

[la poste]

Hi all.

Could anyone tell me if the three phase motor starter on the rig is vulnerable to an IR test at 500V?

I'm really not sure about this one.

I know how to IR test the complete rig but I don't know if putting 500V across L1-E , L2-E, L3-E will damage this starter.

I plan to test from the board first and then IR test from the three phase socket to the starter, you know do the three phase motor circuit in two halves.

Can anyone help me with this?

Thanks.

 

[Brian 157]

Hi all.Could anyone tell me if the three phase motor starter on the rig is vulnerable to an IR test at 500V?

I'm really not sure about this one.

I know how to IR test the complete rig but I don't know if putting 500V across L1-E , L2-E, L3-E will damage this starter.

I plan to test from the board first and then IR test from the three phase socket to the starter, you know do the three phase motor circuit in two halves.

Can anyone help me with this?

Thanks.

Not vulnerable to test but will produce a dead short between the two lines.

Testing in two halves is acceptable.

 

[la poste]

Not vulnerable to test but will produce a dead short between the two lines.Testing in two halves is acceptable.

Why would it produce a dead short between two lines?

The motor is not connected, it is just a three phase socket at the end of the circuit.

The DOL is switched off.

I don't understand where a dead short could come from.

Could you explain?

Thanks.

 

[Brian 157]

The short is between the two phases (lines) the coil circuit is connected to. If you do your IR testing with the contactor pushed in (so you're IR testing the whole circuit) this will produce a short through the coil when you test between those two phases.