Adjustable Voltage Controller

[rollingreenhills]

When I was at school, there was a kid (rest his kind soul) with a disability scooter which had a "tortoise" button on the controls. When you pushed it the speed of the thing would drop, with a big increase in torque.

Say you have 500W motor and run 48V through at 10 amps, would running it at 24V and 20 amps give any advantage in torque. Or dies the controller do this anyway?

If this isn't how the above "tortoise" button worked how do you suppose it did? Two separate motors? Two separate controllers?

Lame question, but my electrical know how is way low.

 

[rollingreenhills]

Bump

 

[Voltron]

Totally a guess, but maybe a delta/wye relay switch?

Edit... Just reread your last sentence, delta and wye are two ways to terminate the windings of a three phase motor, with wye giving lower rpm and more torque. Hooking to a relay that switches between the two essentially gives you two gears.

 

[markz]

Hey Voltron, is that a common setup or would it be quite rare to find?

 

[Voltron]

It would probably be common at a wheel chair shop I would guess.... but in the ebike world not so much. Have you tried searching delta and wye here on ES? It should pull up a few educational threads... It's not something I have a lot of personal experience with.

 

[Gregory]

Anything older than 10 years would certainly have a brushed motor in it.
I guess they'd do the easiest thing and just be switching two SLA batteries from 2S to 2P using a relay.

 

[999zip999]

They have two speed motors I don't know how much more torque.

 

[rollingreenhills]

I have had a look at delta wye, but don't really understand it.

I do understand the series parallel concept, but you would have thought that wit even fairly rubbish SLAs, there would have been plenty of amps in series, so the torque increase would not be so noticeable.

I appreciate your answers. Thanks.

 

[rogervize]

Yes .. delta wye change-over would be my guess as well.
It is certainly a simple way to achieve a 'dual' ratio.
Of course the winding might be under more stress if designed for the higher voltage.

 

[rollingreenhills]

So.

I have heard from reading around that a motor have the most torque, at the lowest revs.

So, if torque increases with a decrease in speed, then this button could have simply been a speed controller?

 

[Voltron]

it could just be a plain old hi low switch... my controller has a three power level plug... but its never on tortoise...lol.