How to make sure you have got the correct rotor fitted

I recently got an email request from a USA dealer asking how to determine one magnetic rotor from another. Fair point, so below is a detailed explanation.

We are starting to see a number of clients buying 2nd hand Whirlpool and F&P parts on Ebay (we can only assume this is to avoid higher freight cost from us), and depending on what stator/rotor combination this can lead is zero generation Watts.

When clients do get the combination correct they rarely balance the rotor and this can cause shaft fretting damage and early bearing failures.

You would we very unwise to buy a stator on Ebay as these we extensively rework to get the voltage correct. A little knowledge can be very dangerous for the DIY’er. Some of these online parts can deliver 1000V at 1000 rpm.

Type 1 rotor

These are earth magnets (all other rotor types are ferrite). Rarely used, likely to see them on reduced core PLT turbines only.

Can be used on all stators that start with 100, 80,60 and do not have “dc” or “R” in the name.

• Maximum output 0.8W/rpm.
• 42 pole stator core
• 56 magnetic poles
• 56 rare earth blocks (1 pole per block)
• Colour: off-white
• Status: very rare
• Interchangeable with: Type 2, Type 2HP

Type 2 rotor

Very common used on all stators that start with 100, 80,60 and do not have “dc” or “R” in the name.

• Maximum output 0.7W/rpm.
• 42 pole stator core
• 56 magnetic pole
• 14 ferrite blocks (4 poles per block)
• Colour: off-white, translucent, light grey, dark grey or brown.
• Status: common
• Interchangeable with: Type 1, Type 2HP

 Type 2 HP rotor

Very rare, used on all stators that start with 100, 80,60 and do not have “dc” or “R” in the name.

Similar to a type 2 above, but this is the HP version. A type 2 HP is a re-magnetized type 3 rotor, so be careful as they are easy to confuse as you can buy a type 3 on Ebay. Type 2 HP have been specially made for us, balanced and corrosion treated.

• Maximum output 1.0W/rpm.
• 42 poles stator core
• 56 magnetic poles
• 16 ferrite blocks (3.5 poles per block)
• Colour: translucent
• Status: rare – premium
• Interchangeable with: Type 1, Type 2

Type 3 rotor

Very common in the USA. If you buy 2nd hand Whirlpool parts on Ebay remember they are not balanced or corrosion treated so can cause shaft fretting damage and early bearing failures. Use on all stators that have “dc” or “R” in the name.

• Maximum output 0.7W/rpm.
• 36 poles stator core
• 48 magnetic poles
• 16 ferrite blocks (3 poles per block)
• Colour: translucent
• Status: common
• Interchangeable with: Type 4HP

Type 4 HP rotor

Available in the USA. If you buy Whirlpool parts on Ebay remember they are not balanced or rust treated, so can cause shaft fretting damage and early bearing failures..

Use on all stators that have “dc” or “R” in the name.

• Maximum output 1.0W/rpm.
• 36 poles stator core
• 48 magnetic poles
• 48 ferrite blocks (1 pole per block)
• Colour: black
• Status: common – premium
• Interchangeable with: Type 3