Repulsion Start Advice

[devonlad108]

Hi guys, i am a newbie here, and would love a bit of advice. I have an old (pre 1950) 3hp motor that needs a new starter. It is a Repulsion Induction motor, and nothing is made like it these days.

I have put an old contactor on it just to see whether it would work, and it starts fine, and doesnt trip the 16A type C breaker. I put an amp clamp on, and the startup current is around 40A, and under no load running, it sits at around 10A

Now, the advice i need is the overload and DOL starter size i would need. I dont know whether an overload rated for its running current would trip out because of the high start draw, or would it allow for a short amount of high current draw? I hope someone knows more about this than me, look forward to hearing from someone!

Jordan

 

[telectrix]

tony's your expert here, but untill he comments, i would say size your overload at 110% of the load current, and your MCB to protect the cable feeding the motor. use a type C . i would think 2.5mm cable with a 16A or 20A MCB.

 

[Knobhead]

Without seeing it this is going to be difficult. Unfortunately you can’t post picture until you’ve made 6 posts (I think). Repulsion start rely on a very high reactance start winding to get it going. Are you sure there isn’t a capacitor connected somewhere?
As for the overloads unless they are magnetic dashpot they should be set at 100%.
I do need as much information as you can give:
Motor makers plate
Starter interior
Anything else that may help

 

[devonlad108]

Right, i dont have the motor here at home, its at a workshop! All i can give you is that it was made by metropolitan vickers. I have uploaded a picture of the dataplate:


The previous starter is now absolutely buggered! It was made with approx 8-10 wound resistors. And as you turn the starter handle around 90 degrees, it would stup up through the resistances, slowly applying more voltage (i guess). Once the handle is at the end of its travel, it is held down with an electromagnet, and it will supply the motor with a full 240v. There is no capacitance that i can see on the motor, but i havnt taken the end cover off yet to look at the commutator.

It will start and run with the full 240v instantly applied with a contactor, but the motor is never under much load, only friction from a few pulleys.

If you need any more info, just ask!

 

[Knobhead]

Interesting, it’s a universal motor of sorts (AC only). Have you had a look at the brushes in it? They will need a good clean out if nothing else and maybe replacing. Now the starter, if it’s beyond hope, you will have to build a new one because it’s the only way you’ll do anything with it. Are the resistances OK? you’ll need them. The starters were faceplate type but without the field control used in a DC starter.

Can you get me a picture of what remains of the starter and the inside of the motor terminal block.

Pitty you're so far away, I'd like to see this.

 

[devonlad108]

I havnt had a look inside the motor at all yet, i will probably go and have a look tommorow. The starter itself is very rusty, and all of the resistances are wound, but covered in rust and shorting all over the place! Last time i saw it used, and subsequently cut the cables to it, blue sparks were covering every bit of metal i could see on the sawbench! the solenoid that holds the handle has burnt out, and is covered in soot, and most of the copper slide contacts have worn and are spinnign and falling out. Its a very nice old piece of kit, but i dont know whether it is worth it, or just plonking a new motor on the side, and getting rid of the old one.

I had a quote for a new 3horse(or Cow)power motor, and with all the switchgear and mounting plate, it came to £560

I will try and get a picture of the starter and motor connections tommorow, see what can be done!

Jordan

 

[Knobhead]

If you seriously want to get this motor running you need to at least renovate the resistors.

BTW this is a Faceplate starter for DC.

 

[Knobhead]

Thinking about this. You could just build a simple triac based starter.

 

[devonlad108]

I may sound slightly thick, but what is a triac based starter?!

 

[devonlad108]

Looking around, im guissing a soft starter is triac based? I had a little look around, and found this PSR16-600-70 - ABB CONTROL - SOFTSTARTER,240VAC,16A | Farnell United Kingdom. Would this suit for my application? If it would the customer would be willing to pay that, im sure. Also, what else would be needed, a DOL starter type setup or just a simple pushbutton on and off?

 

[grantr37]

Interesting, it’s a universal motor of sorts (AC only). Have you had a look at the brushes in it? They will need a good clean out if nothing else and maybe replacing. Now the starter, if it’s beyond hope, you will have to build a new one because it’s the only way you’ll do anything with it. Are the resistances OK? you’ll need them. The starters were faceplate type but without the field control used in a DC starter.

Can you get me a picture of what remains of the starter and the inside of the motor terminal block.

Pitty you're so far away, I'd like to see this.

Seconded, photo(s) of the starter would be good......I have access to various spare parts supply streams.....DHL/Parcelforce comes to mind.....

 

[Knobhead]

They're for three phase. I built a speed controller for a 1KW dc motor years ago. Only cost about £10. If I can find the drawing it can be altered for AC.

 

[devonlad108]

I see, well, if you have a drawing available, i should be capable of building it!

 

[billyfender]

which way is the motor connected? The way the 14A is stamped it looks like A2-A4 &A1-A3 which I would think is for 110v! Is there a shorting ring on the back of the commutator & is this working when motor up to speed

 

[Knobhead]

Bear with me for a day, I spoke to a friend Michelle this afternoon. She's got the IC unit in her lab and lucky for you she doesn't use them anymore.
The starter I built had just the one IC and a 10K pot. It will also need a SPDT switch to change from start to run.

Simples.

But you need to check in the motor bush housing and be sure everything is clean and free.
AND not worn out