120V, 1HP motor control

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Tainted

Tainted

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I am having a notoriously hard to finding a VFD for 120V (input and output) for 1HP motor. The VFD is for a roof exhaust fan. Is there any listed products out there recommended?
 
Tainted said:
I am having a notoriously hard to finding a VFD for 120V (input and output) for 1HP motor. The VFD is for a roof exhaust fan. Is there any listed products out there recommended?
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I don't think I've ever seen a VFD on a single phase motor. Is this a capacitor start motor? What happens when the RPM drops and the starting switch closes? Those capacitors are not rated for continuous use
 
Fans like centrifugal pumps unload as you throttle their flow. A damper might work better. Just be sure the fan's airflow isn't needed for motor cooling
 
Joethemechanic said:
I don't think I've ever seen a VFD on a single phase motor. Is this a capacitor start motor? What happens when the RPM drops and the starting switch closes? Those capacitors are not rated for continuous use
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https://www.grainger.com/product/DAYTON-Centrifugal-Downblast-Roof-4YU95

This is the fan, it's existing. I don't think it's capacitor start but I could be wrong.

LarryFine said:
Why do you feel it's needed?
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Mechanical engineer asked me to put a VFD on the plans for this existing exhaust fan lol
 
Tainted said:
https://www.grainger.com/product/DAYTON-Centrifugal-Downblast-Roof-4YU95

This is the fan, it's existing. I don't think it's capacitor start but I could be wrong.
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I don't think that one comes with a motor. It says to use between a 1/4 and a 1HP motor. No electrical specs listed. Just buy a 3 phase motor for it. Only one more conductor to run

Three phase motors are usually cheaper. Also simpler design and more reliable. No capacitor and no starting switch

BTW a single phase motor in that kind of size without a capacitor would be a very rare bird
 
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Joethemechanic said:
I don't think that one comes with a motor. It says to use between a 1/4 and a 1HP motor. No electrical specs listed. Just buy a 3 phase motor for it. Only one more conductor to run

Three phase motors are usually cheaper. Also simpler design and more reliable. No capacitor and no starting switch

BTW a single phase motor in that kind of size without a capacitor would be a very rare bird
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If I take out the single phase motor and replace it with 3-phase motor, I don't know if it will be compatible with this due to dimension. Dimensions of single phase and 3-phase is different, no?

Is there any drive that that controls a 120V 1hp motor kinda like a VFD? Capacitor start friendly
 
LarryFine said:
Allow me to ask differently: What do you want the motor to do differently than it would if directly powered?
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I'll ask my mechanical engineer, all he said was to specify him a VFD for this fan. I think maybe he wants the fan to automatically run on low during certain times. This fan is on full blast right now 24/7.
 
230525-0026 EDT

Try a Variac with adequate current capacity. Put an ammeter in series with your present fan and then determine full voltage current to the fan. After this lower the voltage to your fan and monitor current. If current runs not more than full voltage, then adjust Variac to adjust fan speed. Fan speed will be quite sensitive the to variations in air load.

You can improve speed control with some sort of speed sensor and voltage adjustment. I believe fan motors are designed with a higher resistance rotor than most other motors. This changes the shape of the motor speed-torque
curve of an induction motor.

.
 
Probably if you call granger and ask for a compatible motor they'll hook you up with the right one. They are usually very helpful
 
Tainted said:
If I take out the single phase motor and replace it with 3-phase motor, I don't know if it will be compatible with this due to dimension. Dimensions of single phase and 3-phase is different, no?
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No. The dimensions of a three phase motor and single phase match as long as they are the same frame size.
Tainted said:
Is there any drive that that controls a 120V 1hp motor kinda like a VFD? Capacitor start friendly
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You can't slow down a cap start motor. You can slow down a Permanent Split Capacitor motor (PSC) but there is no reason to when you can just install a VFD and a three phase motor, or get a multi speed motor like TwoBlocked suggests.
 
ActionDave said:
No. The dimensions of a three phase motor and single phase match as long as they are the same frame size.

You can't slow down a cap start motor. You can slow down a Permanent Split Capacitor motor (PSC) but there is no reason to when you can just install a VFD and a three phase motor, or get a multi speed motor like TwoBlocked suggests.
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I think then I might just call out for a 3-phase motor with VFD. A VFD has an interface to schedule speed of the motor at certain times which is useful. But if I was to get a multi-speed motor do I also have to hook that up to a VFD?
 
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Tainted said:
But if I was to get a multi-speed motor do I also have to hook that up to a VFD?
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No, but most of the two speed motors I see are for applications where the motor is in the airflow. That is how those motors are designed to be cooled. The ventilator you linked to is belt driven and does not have the motor in the airflow
 
Joethemechanic said:
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No, but most of the two speed motors I see are for applications where the motor is in the airflow. That is how those motors are designed to be cooled. The ventilator you linked to is belt driven and does not have the motor in the airflow
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If I get a multispeed motor, how can I program it to run at different speeds at different times automatically? Is it done with a time clock relay?
 
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