Torque or horsepower needed for 3 phase gearmotor, brake, VFD

In summary, using a brushless DC motor with an electronic speed controller, a dynamic or regenerative braking system, and a suitable VFD converter, you can achieve your goal of lifting 500 lbs with a motor, gearbox, and VFD combined weight of 40 lbs or less.
  • #1
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I’ve built a light weight frame for a hoist which only needs to lift around 500 lbs. The cable spool needs to hold 250’ of 3/16 cable that can lift a submersible pump from that depth. The hoist will also be used to develop the well and without going into great detail about this, I’ll just say I need the spool to be variable speed with a holding brake with the RPMS from 0-100. I could do all this with hydraulics which I know more about but I would like to explore the idea of a 3 phase gear motor with a constant brake, reduction to 20:1 gear box and a variable frequency drive. I need help in knowing what minimal horsepower motor I’m looking for and what type of brake would be sufficient to hold the load. Also, I need an adequate VFD converter from 1 phase 115 v to 3 phase 208-230 with some kind speed control by a foot pedal if possible to keep my hands free. Some VFD’s can’t be used above 3,000’ altitude and I’ll be using this at 7,200’ ( a Nema 4 enclosure maybe appropriate because I’ll be using it outside). And to top all this off, I need the motor, gearbox and VFD combined to weigh 40 lbs. or less. Now if there is a simpler way to do this, like a brushless motor with speed control or something, let me know. It needs to be 115 volt system with constant torque with the ability to hold the cable.
 
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  • #2
Thanks for your help.The best way to achieve what you are looking for would be to use a brushless DC motor with an electronic speed controller. This will allow you to adjust the speed of the motor from 0-100 RPM and provide constant torque throughout the full range. A brushless DC motor is much more efficient than a 3 phase AC motor, so you can use a much smaller motor to get the same performance. For example, a 2 pole brushless DC motor with a rated speed of 3000 RPM could provide enough torque to lift 500 lbs at 7200 ft altitude. For the braking system, you could use a dynamic braking circuit or a regenerative braking system, both of which can provide enough torque to hold the load. Finally, for the VFD converter, you would need a single phase 115 VAC input with a three phase 208-230 VAC output, such as the Siemens G120 series. This should provide you with the speed control and power needed to run the motor.
 

1. What is torque and horsepower in relation to a 3 phase gearmotor?

Torque is the measure of rotational force that a motor can exert. It is typically measured in foot-pounds (lb-ft) or Newton-meters (Nm). Horsepower is the unit of power used to measure the rate at which work is done. In the context of a gearmotor, torque is the force required to rotate the gears and horsepower is the power needed to drive the motor.

2. How do I determine the torque and horsepower needed for a specific application?

The torque and horsepower needed for a 3 phase gearmotor depend on several factors, including the load that needs to be moved, the gear ratio, and the desired speed. It is important to consult the manufacturer's specifications and use torque and horsepower calculators to accurately determine the requirements for your specific application.

3. What is the role of a brake in a 3 phase gearmotor?

A brake is a mechanical device used to stop or hold the motion of a gearmotor. In some applications, it is necessary to have precise control over the movement of a load, and a brake can provide that control by stopping the gearmotor from rotating when needed.

4. What is a VFD and how does it affect torque and horsepower?

A VFD (Variable Frequency Drive) is an electronic device that controls the speed and torque of an electric motor by varying the frequency and voltage of the power supplied to it. By adjusting the frequency and voltage, a VFD can increase or decrease the torque and horsepower output of a gearmotor, allowing for more precise control and energy efficiency.

5. Can I use the same torque and horsepower specifications for a 3 phase gearmotor with or without a brake and VFD?

The torque and horsepower requirements for a 3 phase gearmotor may change depending on the presence of a brake and VFD. It is important to consult the manufacturer's specifications and consider the additional torque and horsepower needed to power the brake and VFD when determining the requirements for your specific application.

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