leitmotif
Member
CONCEPT is to use off the shelf VFD as low cost method to do proportional control on heaters. I know you can use relays and turn on/off more heaters - which may work fine
BUT this is "step" control not "variable / proportional control"
Basically turn up the speed output of the VFD and get more power to the heaters.
Heaters would have to operate in "threes" and they would have to closely match each other unless recified.
VFD output could be rectified to reduce noise problems. In this case recifiers would have to closely match each other.
Lessee
REASONS WONT WORK
1. Motors are not heaters. VFD controls motors.
2. VFD would not get back (or be able to calculate them) speed signals from motor. Therefore would trip.
3. VFD may not go low enough on voltage to give low range control of heaters. Has to have enough volts to get motor to roll at low frequency (RPM).
4. Rectifiers cannot handle the hi freq carrier signal ??
5. VFD requires other signals or calculations from a motor that a heater setup cannot replicate??
REASONS COULD WORK
1. VFD has variable output both frequency of pulses and magnitude of pulse. Combination of two is power.
2. Heaters don't care about frequency. Besides they would be fed off rectified VFD output.
3. Pulse control is used on heater applications is it not? VFD basically produces a pulse.
4. In limited research have not found anything saying it cannot be done.
Thoughts ??
Dan Bentler
BUT this is "step" control not "variable / proportional control"
Basically turn up the speed output of the VFD and get more power to the heaters.
Heaters would have to operate in "threes" and they would have to closely match each other unless recified.
VFD output could be rectified to reduce noise problems. In this case recifiers would have to closely match each other.
Lessee
REASONS WONT WORK
1. Motors are not heaters. VFD controls motors.
2. VFD would not get back (or be able to calculate them) speed signals from motor. Therefore would trip.
3. VFD may not go low enough on voltage to give low range control of heaters. Has to have enough volts to get motor to roll at low frequency (RPM).
4. Rectifiers cannot handle the hi freq carrier signal ??
5. VFD requires other signals or calculations from a motor that a heater setup cannot replicate??
REASONS COULD WORK
1. VFD has variable output both frequency of pulses and magnitude of pulse. Combination of two is power.
2. Heaters don't care about frequency. Besides they would be fed off rectified VFD output.
3. Pulse control is used on heater applications is it not? VFD basically produces a pulse.
4. In limited research have not found anything saying it cannot be done.
Thoughts ??
Dan Bentler