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Rolls-Royce Show Engine Motor Controller

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Duncan Morrison

New Member
Hello

I am currently building a show engine for the new Rolls-Royce which is going to be powered by a single phase 220v 50Hz motor. I have not purchased a motor yet but it will probably be rated at 2.5kW.
I would like the speed of the motor to be variable and the speed controlled via the existing cars gas pedal. The pedal uses a hall sensor which from what i can gather works the same as a variable resistor but there is no physical electrical connection. The hall sensor has an input of 5v and the output varies between 750mV and 4500mV. The output increses with pedal travel.
Can anyone please help me design a circuit
 

crust

Member
I dont think anyone will do the whole thing for you, perhaps you should attack the parts you know and ask about the others.

I'll offer this, there are many types of AC motors. In many cases, the easiest way to change their speed is to alter the frequency of the applied AC. Its sometimes called variable frequency drive.

As for the hall effect sensor, it seems that your is outputting a voltage which depends on the proximity of a magnet which is probably mechanically coupled to the pedal somehow. To get these working together, you just need some interface circuitry. Perhaps a micro which reads an ADC from your pedal sensor and controls the frequency of a PWM system.
 

Russlk

New Member
The design will be greatly simplified if you use a DC motor. Speed control of AC motors is difficult, unless you use a universal (AC/DC) type which is probably not available in the power rating you need. The system will need a tachometer for feedback, altho there is a method of using the motor itself as the tach. If you have 3 phase power available, that would simplify the AC to DC conversion. I will try to post a block diagram here to show what I have in mind.
 

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panic mode

Well-Known Member
Speed control is very dificult for single phase motors.
If you want to use mains, use three phase and VFD.
Note that many motors do not like running at very low
speeds unless they are designed for it (they get sufficient
cooling) or you ensure forced air circulation which is
much better than what you get with intefrated fan.
For example SEW (Eurodrive) makes very robust VFDs
(Variable Frequency Drive). I like Allen Bradley's 160's
series as well but they are far more sensitive for sudden
load changes and they cost about double of what you get
from SEW.
 

Duncan Morrison

New Member
VFD's

Thank you guys for all your help, i have been looking at the SEW Eurodrive motors and movitrac control units. The problem with these control units is that i wanted to vary the speed of the motor using the cars existing gas pedal which contains a hall sensor. If i buy one of these sew eurodrive vfd's do you think it could be modified so i can use my existing pedal?
 

panic mode

Well-Known Member
That should be no problem. Do you know what is the signal from pedal?
 
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