That should work.
The only issue is that the motor will have a higher starting current than 3A which might cause one of the supplies to current limit which might destroy it as it will be then connected to 48V backwards. To protect against this, connect a 3A diode in reverse parallel with each power supply and start the motor slowly.
The power supplies should be permanently wired together so it's not possible to only power one of them up.
The only issue is that the motor will have a higher starting current than 3A which might cause one of the supplies to current limit which might destroy it as it will be then connected to 48V backwards. To protect against this, connect a 3A diode in reverse parallel with each power supply and start the motor slowly.
The power supplies should be permanently wired together so it's not possible to only power one of them up.
Oh no, I've just figured out what you intended to do. I didn't notice the AC symbol on the motor controller you linked to but looking it again and your diagram make me notice it.
No that won't work, the speed controller needs to be on the output of the power supplies (not the input) and designed for DC voltage, not AC.
The power supplies will try to keep their output voltage near 24V, regardless of the input voltage so varying the input voltage will not work. The power supplies are not simple passive transformers but active switch mode power supplies which will be designed to take any voltage between 90V and 250VAC and convert it to a steady 24VDC. In practice what is likely to happen is the TRIAC (electronic switch) inside the speed controller will be destroyed by the capacitive load; the speed controller will be designed for motors which are inductive but the power supplies will be capacitive as they will have huge filtering capacitors on the input.
You need a 90VDC speed controller unit but make sure it's specified to at least 100VDC maximum: connect the speed controller between the motors and the 96VDC power supply you've just made from three 24VDC power supplies.
No that won't work, the speed controller needs to be on the output of the power supplies (not the input) and designed for DC voltage, not AC.
The power supplies will try to keep their output voltage near 24V, regardless of the input voltage so varying the input voltage will not work. The power supplies are not simple passive transformers but active switch mode power supplies which will be designed to take any voltage between 90V and 250VAC and convert it to a steady 24VDC. In practice what is likely to happen is the TRIAC (electronic switch) inside the speed controller will be destroyed by the capacitive load; the speed controller will be designed for motors which are inductive but the power supplies will be capacitive as they will have huge filtering capacitors on the input.
You need a 90VDC speed controller unit but make sure it's specified to at least 100VDC maximum: connect the speed controller between the motors and the 96VDC power supply you've just made from three 24VDC power supplies.
http://www.simplecircuitdiagram.com/2009/05/04/motor-speed-control-using-pwm/
Could this circuit be used to control 100v DC by upgrading the MOSFET to say the IRF540N?
D.
Could this circuit be used to control 100v DC by upgrading the MOSFET to say the IRF540N?
D.
Yes, I've built a similar circuit to that before and it works well.
In your case you have a problem: the maximum rating of the NE555 is 16V, so will need to be powered by a separate regulator. Tap 24VDC from the first PSU and connect it to the 555 via an LM78L12 or LM7812 with the appropriate decoupling capacitors: see LM7812 datasheet.
The circuit contains an error: the operating voltage range of the LM555 is 4.5V to 16V, not 3V to 18V and the supply voltage needs to be over 10V to turn the MOSFET fully on.
For some reason they've decided to connect the MOSFET to pin 7 (discharge) and use a pull-up resistor, rather than to pin 3 (output) which would drive the MOSFET more efficiently. Remove R2 (leave pin 7 unconnected) and connect the MOSFET's gate (pin 1 on Q1) to pin 3 on the 555 via a 100R resistor.
In your case you have a problem: the maximum rating of the NE555 is 16V, so will need to be powered by a separate regulator. Tap 24VDC from the first PSU and connect it to the 555 via an LM78L12 or LM7812 with the appropriate decoupling capacitors: see LM7812 datasheet.
The circuit contains an error: the operating voltage range of the LM555 is 4.5V to 16V, not 3V to 18V and the supply voltage needs to be over 10V to turn the MOSFET fully on.
For some reason they've decided to connect the MOSFET to pin 7 (discharge) and use a pull-up resistor, rather than to pin 3 (output) which would drive the MOSFET more efficiently. Remove R2 (leave pin 7 unconnected) and connect the MOSFET's gate (pin 1 on Q1) to pin 3 on the 555 via a 100R resistor.
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