Fused Wadkin

[robsredhunter]

Hi, I've recently bought a 10" single phase wadkin saw that I can't start more than twice without blowing the fuse. the previous owner had 'cured' the problem by substituting a short length of steel bar of the same diameter. This is a bodge too far even for me, I'm no electrician so if anyone has any ideas on what's causing the problem I'd appreciate the feedback. I notice that inside the start box there are 3 adjustment knobs and the words Full Load Amps, there's a small window with an indicator bar that seems to be set at 16 amps, could this be relevant?

 

[Digit]

My word but that's an old starter!
You need a 16 or 20 amp supply my friend.

Roy.

 

[fobco]

hi,i had the same problem,it turned out the belts was to tight,it was drawing to much power to get it going,it kept blowing the fuse,slackened off the belts a little,know more trouble

 

[DaveL]

Hi robsredhunter,

Welcome to the forum.

It sounds like you have a 3Hp motor on that Wadkin, that's what I fitted to mine when I converted it to single phase. The type of starter will determine if it will start on a 13 amp fuse, mine wont, even with no belts on. The start current on my motor is ~3 time the full load current, so I have a 16 amp supply for it.

The adjustments you have found is the overload protection, which if you do have a 3Hp motor sound like its set a bit high. See if you can find a plate on the motor, it should give details of the power of it and the full load current. It may not be easy to read with the blade fully raised, lowering the blade will let you see the top of the motor.

 

[Digit]

If slackening the belts solved the problem that would suggest that the belts were so tight that the motor pulley bearing was under a considerable side load, or alternatively the belts are currently slipping on start up.

Roy.

 

[Tusses]

mine is 1.5Hp and has blown the fuse once so far in the month Ive had it. I was running it off of a couple of cheap extension leads.

start up current is the highest and if your supply cable is a bit under rated (or running of a thin extension lead )then the voltage will drop and the motor will take longer to spin up and so blow the fuse.

that is my theory anyway.

Its been fine of my 16a lead.

 

[Digit]

As I pointed out on another thread the load to be spun is what causes the motor to draw too high a current for too long. If there is a source of extra friction, such as loaded bearings, this all adds to the time taken to come up to speed.
A 13amp fuse will not blow at 13 amps, the rated working level for cartridge fuses is (was) 150 % of the fuse rating. So a 13 amp fuse should only blow if the current exceeds 20 amps for the rated period of time for that fuse.

Roy.

 

[misterfish]

When I got my Wadkin single phase saw it used a standard 13 amp fused plug that the previous owner had modified to replace the cartridge fuse with what looked like very thick fuse wire. I wasn't happy with this!

When I set up my workshop I wired the saw into a dedicated 16 amp MCB controlled circuit. I had problems with this regularly tripping on startup as the initial surge took too much current. I replaced the type 'B' circuit breaker with a type 'C' (apparently for machinery that causes an initial current surge) and I haven't had a problem since.

Misterfish

 

[herdsman]

When I set up my workshop I wired the saw into a dedicated 16 amp MCB controlled circuit. I had problems with this regularly tripping on startup as the initial surge took too much current. I replaced the type 'B' circuit breaker with a type 'C' (apparently for machinery that causes an initial current surge) and I haven't had a problem since.

Misterfish

The class B mcb is for resistive loads (heating elements) which have a lower surge when turned on than inductive loads (motors, fluorescent lights). If the motor is rated at 16 amps single phase then it should be connected to a 16 amp single phase supply. The size of cable needs to be calculated to take into account any voltage drop because this will in turn cause the drawn current to increase. This can cause undersized cables to get warm and possibly overheat and catch fire. The DIY fuse replacement as mentionend in an earlier post is therefore potentially lethal.

 

[robsredhunter]

Hi people, thanks for all the feedback, I think we may be onto something with the overloaded startup. I didn't think about the belt tension when I rehung the (heavy) motor. I've slackend things off which has improved matters, though it's not a total fix. I thought I might open up the motor to see the condition of the commutator and brushes and bearings, that is if penetrating oil ever works is magic on the stuck fan. The motor is 2 horse power and is stamped FL (presumably Fully Loaded) 11 amps, does that need a 16 amp supply? I would prefer not as this would involve a lot of aggro. Thanks

 

[Digit]

I would not expect a motor of that size to have a com. Just take the belt off, start then stop the motor and listen to see if it is noisy and how long it takes to slow down.
If it is quiet and takes time to slow I think you can discount motor problems.
11 amp doen't really tell us anything 'cos as I pointed out earlier the motor will be slower running up 'cos of the inertia of the drive train and blade.
If the motor passes the above test ok check the rest of the drive train is free, if it is you need a heftier supply.
If you are running on a ring main a dedicated line would be needed, if you are running on a supply that serves only the saw it may only require a 16 amp plug and socket.

Roy.