Induction motors.

[whiskywill]

I have a Charnwood W730 band saw that starts off slowly but quickly builds up to full speed. Am I right in thinking that the initial slow start is because of the load on the motor?

 

[scotty38]

Is it possibly just a soft start motor?

 

[Argus]

Unlikely to be a loaded up start. Direct drive band saws start with a minimum load anyway - just the bearing friction of the drive, belts and the saw blade. It loads up as soon as you put a chunk of wood through it.
You should be able to check it by seeing if the blade moves freely by hand when stopped (and unplugged).

You don't mention how it performs when 'up to speed', but having eliminated any seizures or tightness in that lot before you introduce wood, I would look first to the Start /Run capacitor, it being relatively inexpensive to replace.
The other simple and basic check that does not involve meters is to Run it for 10 minutes or so then check the external temperature of the motor. As a rule of thumb, it should be hot enough to touch, but not uncomfortable.

The wiring diagram that I have seen on line - http://www.manualslib.com/manual/758536 ... =13#manual - shows a 25 mF / 450V capacitor.
Capacitors are difficult to check without at the very least an old fashioned analogue multimeter, but are not expensive to buy.

Just a few basic things to eliminate...... good luck.

 

[Andy RV]

Unlikely to be a loaded up start. Direct drive band saws start with a minimum load anyway - just the bearing friction of the drive, belts and the saw blade. It loads up as soon as you put a chunk of wood through it.

There is load at start up as the motor has to spin the wheels up to speed!

The behaviour described sounds completely normal. Big bandsaws can take a reasonable time to come up to full speed. A band resaw is a great example of this.

 

[CHJ]

A small 14" bandsaw like the Charnwood W730 should snap up to speed with very little discernable lag.

Assuming that as already mentioned all moves freely by hand when stationary then I would first check that the drive belt is not slipping, although this would normally be accompanied with blade slowing down in use, failing that as previously mentioned the start/run capacitor is favourite.

 

[niagra]

My Myford lathe used to do that, I renewed the knackered mounting bushes (can't remember the exact name) for the motor and it now gets to speed pretty much immediately.

 

[Argus]

I have a Charnwood W730 band saw that starts off slowly but quickly builds up to full speed. Am I right in thinking that the initial slow start is because of the load on the motor?

Whatever it turns out to be, don't forget to let us know when you get it fixed :wink: :wink:

 

[whiskywill]

Is it possibly just a soft start motor?

No mention of that in the manual.

 

[whiskywill]

Unlikely to be a loaded up start. Direct drive band saws start with a minimum load anyway - just the bearing friction of the drive, belts and the saw blade. It loads up as soon as you put a chunk of wood through it.
You should be able to check it by seeing if the blade moves freely by hand when stopped (and unplugged). It can be pulled around by hand but not as easily as my other smaller band saw.
You don't mention how it performs when 'up to speed', but having eliminated any seizures or tightness in that lot before you introduce wood, When up to speed it performs very well with no slowing down when the wood is being cut. I would look first to the Start /Run capacitor, it being relatively inexpensive to replace.
The other simple and basic check that does not involve meters is to Run it for 10 minutes or so then check the external temperature of the motor. As a rule of thumb, it should be hot enough to touch, but not uncomfortable. I will try this.

The wiring diagram that I have seen on line - http://www.manualslib.com/manual/758536 ... =13#manual - shows a 25 mF / 450V capacitor.
Capacitors are difficult to check without at the very least an old fashioned analogue multimeter, but are not expensive to buy.

Just a few basic things to eliminate...... good luck.

 

[whiskywill]

A small 14" bandsaw like the Charnwood W730 should snap up to speed with very little discernable lag..

It is only a small but noticeable lag of about 2 seconds.