In the late 1960's, active in R&D @ Philips Power Electronics, I developed a working prototype for a speed variable wound rotor induction motor, where:
- the classical variable resistances (rheostats) were replaced by a chopper with variable duty cycle (the thyristor was just there, my job was to find applications for it...)
- the chopper was built into a cylindrical shape and was made solidary of the rotor
- the speed setting was transmitted magnetically from the stator to the rotor
- the slip energy was dissipated, which was deemed acceptable for a fractional horse power motor (less than 1 HP) : the market segment objective
- I found a way to collect and dissipate the slip energy. An air transformer was buit with a single winding secondary, shorted and finned. This aluminum secondary had a lateral 'U' shaped crossection. The chopper coil, the primary of the air transformer, was slid in this U shaped cavity, the shorted cooled secondary. Both were potted into one solid component.
Philips wrote 4 patent applications to cover this.
A good team was assembled with SUBEM, a Belgian induction motor producer (the second in revenue). The project was stopped by Philips for political reasons. I left the company, disappointed, and went on.
I very much would appreciate your comments !
Did you come across a scheme like this ?
Very cordially,
- the classical variable resistances (rheostats) were replaced by a chopper with variable duty cycle (the thyristor was just there, my job was to find applications for it...)
- the chopper was built into a cylindrical shape and was made solidary of the rotor
- the speed setting was transmitted magnetically from the stator to the rotor
- the slip energy was dissipated, which was deemed acceptable for a fractional horse power motor (less than 1 HP) : the market segment objective
- I found a way to collect and dissipate the slip energy. An air transformer was buit with a single winding secondary, shorted and finned. This aluminum secondary had a lateral 'U' shaped crossection. The chopper coil, the primary of the air transformer, was slid in this U shaped cavity, the shorted cooled secondary. Both were potted into one solid component.
Philips wrote 4 patent applications to cover this.
A good team was assembled with SUBEM, a Belgian induction motor producer (the second in revenue). The project was stopped by Philips for political reasons. I left the company, disappointed, and went on.
I very much would appreciate your comments !
Did you come across a scheme like this ?
Very cordially,