Hi all, first post here, I hope power electronics is the right place in the forum to post this, mainly due to the voltages involved.
I ask for help and guidance here with this design as I am a bit rusty with electronics and haven't built devices in this voltage area before. I didn't want to plough straight in and cause damage to the motor or anything/anyone else, hoping this post is the start of my research, and will point me in the right direction. I realise this is a big ask, and I'm not expecting anyone to have the time to sit down and fully design me a motor controller, but I need a steer in a good direction from someone with the right experience, who knows what pitfalls to look out for.
These motors are inside aircraft cockpit indicators and display units, so are only small, they drive light gear trains to move cards and pointers in the indicators. This is part of a flight simulator personal project using real equipment form the 1960's. I am not going to be modifying the equipment by changing the motors for modern equivalents, as the notion of historic preservation is at the heart of this project.
Note: These are not modern quadrature phase stepper motors, I don't think a square wave pattern would be suitable as used in stepper motors.
The motors in question are quadrature phase motors; they have two windings, one [reference] "REF" (115V RMS) and one "CONTROL" (60V RMS), both 400Hz.
I have a 28Vdc to 115Vac 400Hz rotary inverter, so can provide a clean sine wave to the REF coil with no problem.
I now have the issue of providing a controlled signal to the CONTROL coil to operate the motors correctly.
CONTROL coil signal specification:
CONTROL coil driver output stage:
I imagine the output stage to be achieved by a push/pull setup between +84V DC and -84V DC power supply rails (60V AC RMS * 1.4 for peak value), possibly PNP/NPN complimentary pair, IGBT or MOSFET, or other device, advice on which would be most suitable, and simplest to design would be appreciated.
These motors are only small, <1" diameter by about 2" long, and drive light loads, so I can't imagine a high current draw - but I will not know a typical current until I get prototyping, however, I'd aim at a capability of around 1A to 2A initially to ensure startup torque, or direction reverse torque doesn't damage the driver output stage devices.
Driver REF voltage sensing:
The driver will need to sense the 115V AC REF voltage in order to correctly offset the CONTROL signal 90 degrees out of phase. I can use a transformer to reduce the voltage to safer levels, but am open to other ideas here too involving other means of isolation, but it should not cause a delay / phase shift.
Interface:
The driver circuit must be able to be operated by an Arduino board / Arduino compatible ATMEL IC. The 400Hz frequency of this driver is outside of the native PWM speed capabilites of the typical Arduino board, so I am envisaging a separate dedicated driver interfaced by I2C or 0 to 5V, or other compatible signal.
If I2C is used, between Arduino and driver, as multiple drivers will be in use, addressable drivers are needed for sharing one bus.
I am interested to know if there is an easy off-the-shelf idea that would work for parts of this application such as the push/pull output stage to save time and going round in circles, but any design advice on the above points is sought please to achieve this in the most painless way.
Many thanks, Scott.
I ask for help and guidance here with this design as I am a bit rusty with electronics and haven't built devices in this voltage area before. I didn't want to plough straight in and cause damage to the motor or anything/anyone else, hoping this post is the start of my research, and will point me in the right direction. I realise this is a big ask, and I'm not expecting anyone to have the time to sit down and fully design me a motor controller, but I need a steer in a good direction from someone with the right experience, who knows what pitfalls to look out for.
These motors are inside aircraft cockpit indicators and display units, so are only small, they drive light gear trains to move cards and pointers in the indicators. This is part of a flight simulator personal project using real equipment form the 1960's. I am not going to be modifying the equipment by changing the motors for modern equivalents, as the notion of historic preservation is at the heart of this project.
Note: These are not modern quadrature phase stepper motors, I don't think a square wave pattern would be suitable as used in stepper motors.
The motors in question are quadrature phase motors; they have two windings, one [reference] "REF" (115V RMS) and one "CONTROL" (60V RMS), both 400Hz.
I have a 28Vdc to 115Vac 400Hz rotary inverter, so can provide a clean sine wave to the REF coil with no problem.
I now have the issue of providing a controlled signal to the CONTROL coil to operate the motors correctly.
CONTROL coil signal specification:
- 60V RMS, 400Hz sine wave (or fast PWM approximation of a sine wave, some tens of kHz I imagine).
- 90 degree Lead or Lag w.r.t. REF signal. Lead / Lag will control the direction of shaft rotation.
- Variable amplitude, could be achieved using above fast PWM concept. Amplitude controls the motor speed, CONTROL signal at 0V = shaft static; 60V RMS = maximum shaft speed.
CONTROL coil driver output stage:
I imagine the output stage to be achieved by a push/pull setup between +84V DC and -84V DC power supply rails (60V AC RMS * 1.4 for peak value), possibly PNP/NPN complimentary pair, IGBT or MOSFET, or other device, advice on which would be most suitable, and simplest to design would be appreciated.
These motors are only small, <1" diameter by about 2" long, and drive light loads, so I can't imagine a high current draw - but I will not know a typical current until I get prototyping, however, I'd aim at a capability of around 1A to 2A initially to ensure startup torque, or direction reverse torque doesn't damage the driver output stage devices.
Driver REF voltage sensing:
The driver will need to sense the 115V AC REF voltage in order to correctly offset the CONTROL signal 90 degrees out of phase. I can use a transformer to reduce the voltage to safer levels, but am open to other ideas here too involving other means of isolation, but it should not cause a delay / phase shift.
Interface:
The driver circuit must be able to be operated by an Arduino board / Arduino compatible ATMEL IC. The 400Hz frequency of this driver is outside of the native PWM speed capabilites of the typical Arduino board, so I am envisaging a separate dedicated driver interfaced by I2C or 0 to 5V, or other compatible signal.
If I2C is used, between Arduino and driver, as multiple drivers will be in use, addressable drivers are needed for sharing one bus.
I am interested to know if there is an easy off-the-shelf idea that would work for parts of this application such as the push/pull output stage to save time and going round in circles, but any design advice on the above points is sought please to achieve this in the most painless way.
Many thanks, Scott.