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pengyou   1 kW

1 kW
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Location: Beijing


Post by pengyou » Sep 12 2018 7:00am

I am going nuts searching for an answer to my question..I'm sure the answer is right before my eyes. what does 35H and 40H mean when describing electric motors?

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fechter   100 GW

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Re: 35H??

Post by fechter » Sep 12 2018 8:19am

That is the rating of the magnets. 40H are stronger than 35H. A stronger magnet is not always better as it increases the eddy current losses in the stator. Stronger magnets are better if you want maximum torque at the expense of speed.

See: https://en.wikipedia.org/wiki/Neodymium_magnet
"One test is worth a thousand opinions"

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spinningmagnets   100 GW

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Re: 35H??

Post by spinningmagnets » Sep 12 2018 8:55am

It was my understanding that when a direct drive hubmotor is shown on its side, the "H" is for the "Height" of the lamination stack. If you visualize the hubmotor in its vertical normal orientation when it is mounted on the bicycle, we might call it the "width" of the lamination stack. It designates 35mm wide. When the copper phase wire is wrapped around the stator tooth, it becomes an electromagnet that can be turned on and off. The width of that electromagnet determines how much power it has.

The permanent magnets in the rotor (motor rim) are typically exactly the same width as the stator. However there have been several times when a motor was found to be a millimeter or two wider than the magnets.

The 35H hubmotors are the most popular direct drive style, because they will fit on a normal bicycle frame with the common drop-out width of 135mm, and they will also still easily fit a 6-speed freewheel / derailleur system (and sometimes a 7-speed).

The narrower 28H direct drive hubmotors are usually only found in the cheapest ebay kits. They have thick laminations and thin phase wires, and they can only only survive modest power levels, unless you do something to release the excess heat that builds up. The quality is typically average at best. If you are limited to 2,000W or less, then you might be better served by any one of the several large geared hubmotors. They provide good torque from a smaller and lighter motor, as long as you don't overheat them.

The 35H motors are appropriate from around 48V X 50A = 2500W, up to around 5,000W peaks (as long as you keep an eye on the temps). If you add ferro-fluid, that helps it shed heat, and you can apply even more power.

If the 35H motors are overheating in your particular application, then you might need a bigger motor. The most popular next size up is the 45H MXUS 5K turbo. As the name implies, it is rated for 5,000W

The QS and Cromotor are both 50H (if I recall correctly), but that also means they are heavier and more expensive. If you are looking at 35H hubmotors, I highly recommend getting two well-made torque arms. If you do not, you will likely regret it it later.

markz   100 GW

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Re: 35H??

Post by markz » Sep 12 2018 3:14pm

The most popular next size up is the 45H MXUS 5K turbo.
Most popular I would say is the 3000W MXUS XF40-45H, but it is always nicer to get more power with the 55H 5kw motor too ;)

5000W MXUS - https://mxus.en.alibaba.com/product/607 ... 3412dWNpEV
^^^Be aware that the 5kw mxus motor requires a non standard rear dropout width, I believe its like 155-160mm where standard bicycles are 135mm.

3000W - https://www.alibaba.com/product-detail/ ... 3412RqhrU3
^^^ Will fit in the standard 135mm rear dropout, but will require less gears/speeds. I am running a single geared freewheel, but have run 5 speed freewheel, no problem. However for the last while I have been running with no chain for no reason, foolish in a way because if I run outta juice, no dice.


Another example: Crystalyte H3540

The Leafbike / Leafmotor 1500W can pump out a ton of power too. Looks like it is 35H.
Link - http://www.leafbike.com/products/diy-bi ... t-989.html

Be aware that some numbers like the Phoenix motors are stating the amps and voltage.
Example: 72V 40A bottom orange.
hs.jpg (109.26 KiB) Viewed 344 times

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