That is nichrome wire and can dissipate huge amounts of in rush current, whilst glowing red and will then cool down once things stabilise.
A bit like the wire in toasters.
A resistor will be unlikely to cope, unless a wirewound fitted to a heatsink.
A bit like the wire in toasters.
A resistor will be unlikely to cope, unless a wirewound fitted to a heatsink.
That style relies on a good heat sink with efficient thermal conduction between the resistor body and the sink.
This would be unlikely with a cast iron enclosure, so considerable derating of the resistor would be necessary.
Use more than one, spread apart on the casting.
This would be unlikely with a cast iron enclosure, so considerable derating of the resistor would be necessary.
Use more than one, spread apart on the casting.
I guess I should probably abandon the whole idea of two speeds and just wire the AC cable directly to the motor to run full speed all the time. I may try to source original speed coil but that may be an impossible task. Other than that, I can try the resistor and test it by measuring temperatures it creates.
It appears the original speed coil former was made of asbestos. It was in common use back then, even through the 1960s.
Hey, try with non-polar capacitor in series with mains wire, begin from let's say 4,7uf and increase or decrease capacity upon results. Capacitor will dissipate allmost no heat ( if they heats up, fails ) . There are motor start capacitors of variuos capacity available , and voltage rating must be at least 2-3 times more your ac voltage rating. I would choose 450V AC rating. Also you may try with film capacitors, several in parallel, same voltage rating. I'm suggesing this as i i've had something similar, 220V fan, and there were several capacitors installed inside base pad, and two rocket switches as speed selector .
Those are caps that create an extra phase by phase shifting, to allow the motor to run from a single phase AC mains.
These are not meant to regulate or modify the speed.
They are called 'motor run capacitors'.
Jan
These are not meant to regulate or modify the speed.
They are called 'motor run capacitors'.
Jan
When using a fan to keep cool, it seems counterproductive to use resistors that generate lots of heat..
Well small single-phase induction motors are very inefficient anyway, generating a lot of heat compared to a permanent magnet motor say. Large induction motors are 3-phase and get more efficient, but that means large (measured in horsepower).
The design of induction motors is complicated especially if some form of speed limiting is involved, the geometry of the buried windings in the rotor and rotor-stator air-gap width have a lot of influence on motor characteristics, and you presumably haven't got a detailed datasheet!
For instance you can make a motor that can handle continuous stall, but most will simply cook themselves if you do that. Fans are usually designed under the assumption that they can't stall as air is a fluid. Older fans might not be safe if the bearings sieze and they do stall - they could potentially catch fire. Modern fans will be designed with inherent safety or a thermal cutout to meet regulations. Assuming a reputable brand.
The design of induction motors is complicated especially if some form of speed limiting is involved, the geometry of the buried windings in the rotor and rotor-stator air-gap width have a lot of influence on motor characteristics, and you presumably haven't got a detailed datasheet!
For instance you can make a motor that can handle continuous stall, but most will simply cook themselves if you do that. Fans are usually designed under the assumption that they can't stall as air is a fluid. Older fans might not be safe if the bearings sieze and they do stall - they could potentially catch fire. Modern fans will be designed with inherent safety or a thermal cutout to meet regulations. Assuming a reputable brand.
You may find full speed too fast for regular use. Especially if your mains voltage is higher than when the fan was made.
Then your back to reducing voltage (but without the switch).
I'd experiment with buck transformer assuming you have some low voltage transformers in your parts stash.
If it works then you can look to tidying it up into a proper solution.
Transformer could be in a box on the floor near the plug (out of the way).
Alternatively, you could deepen the base of the fan by profiling a stack of ply. Wouldn't take much for a small transformer. Then you incorporate a switch for speeds.
Then your back to reducing voltage (but without the switch).
I'd experiment with buck transformer assuming you have some low voltage transformers in your parts stash.
If it works then you can look to tidying it up into a proper solution.
Transformer could be in a box on the floor near the plug (out of the way).
Alternatively, you could deepen the base of the fan by profiling a stack of ply. Wouldn't take much for a small transformer. Then you incorporate a switch for speeds.
The base is not super small. Here is a photo of it plus another one with a deck of cards. The deck almost fits height-wise. I just have no idea what transformer to use and what specs should I look for. All I know that the original speed coil had two resistances (10 Ohm for medium and 15 Ohm for slow speed). And you are probably right, the mains voltage was probably 110-115V vs today's 120V. Would anybody be kind enough to link a suitable transformer from Amazon, Mouser or another US retailer? One slower speed is fine for me.
Rod Elliott has a guide on buck transformers:
https://sound-au.com/
https://sound-au.com/articles/buck-xfmr.htm
See Fig 4.
You can put multiple secondary windings in series.
Try a 2 x 20V secondary. This would give available running voltages of 120/105/90 assuming 120V in.
You would want to switch off the mains when not in use else the transformer would be continuously energised.
For safety, use a 3-core cable and ensure your fan base is earthed.
I say this because vintage gear may have originally used a 2-core cable and not have a safety earth.
Vintage look braided cable is available made to modern insulation standards.
https://sound-au.com/
https://sound-au.com/articles/buck-xfmr.htm
See Fig 4.
You can put multiple secondary windings in series.
Try a 2 x 20V secondary. This would give available running voltages of 120/105/90 assuming 120V in.
You would want to switch off the mains when not in use else the transformer would be continuously energised.
For safety, use a 3-core cable and ensure your fan base is earthed.
I say this because vintage gear may have originally used a 2-core cable and not have a safety earth.
Vintage look braided cable is available made to modern insulation standards.
Note, only the secondary carries the full current of the motor.
So, even if drawing the full 1.3Amps stated in post 1, with 2 x 20V windings in series you would have 40 x 1.3 = 52VA.
Ideally you want a transformer to try so you can see if you want to go higher or lower with the voltages.
So, even if drawing the full 1.3Amps stated in post 1, with 2 x 20V windings in series you would have 40 x 1.3 = 52VA.
Ideally you want a transformer to try so you can see if you want to go higher or lower with the voltages.