Tension control is a specialized area that can be quite challenging to implement effectively. Choosing the right motor type is the first critical step towards achieving success. Contrary to popular belief, you don’t always need to opt for a servo motor for this purpose.
Consider the following application illustration where two motors work together to maintain tension and feed material simultaneously. The smaller brushless motor in the middle is responsible for winding, while the larger torque motor provides a precise level of tension.
Applications such as film winding, stamping/pressing, and screw tightening often require the motor to regulate or limit its torque:
- **Film Winding/Unwinding:** Requires the motor to adjust its torque dynamically based on the roll diameter to ensure consistent tension.
- **Stamping/Pressing:** Requires the motor to limit its torque to avoid damaging delicate items, such as breaking eggs during label stamping.
- **Screw Tightening:** Requires the motor to limit its torque to prevent exceeding the maximum allowable tightening torque for the screw.
While servo motors are commonly chosen for tension control applications due to their versatility, there’s a cost-effective alternative worth considering if you don’t need all the extra features.
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**Torque Motors**
Torque motors resemble standard induction motors but differ significantly in their design and functionality. They’re engineered to control torque and can endure continuous stalling or even back-driving without overheating, making them essential for tension control tasks.
A torque motor achieves full torque at zero speed and is seldom used at full speed. Unlike an induction motor, it employs a balanced winding and a high-slip rotor rather than a low-slip rotor. This high-slip rotor design allows the motor to function as a brake when back-driven. Despite their small size, which tops out at 20W, torque motors come with various gear ratios to amplify torque. Single-phase 110/115VAC and 220/230VAC options are also available.
For instance, given a certain load, applying voltage V4 to the motor will cause it to limit its output torque at the point where the "V4" line intersects the "Load" line, resulting in a running speed of "N4."
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Unlike a servo motor tension control system, a torque motor does not require motor feedback or additional sensors to manage its torque. All you need is a device capable of varying the input voltage to the motor, such as the **TMP-1 power controller**.
The TMP-1 power controller uses the triac phase control method to adjust the voltage supplied to the torque motor. Alternatively, any device that can output a stable voltage to the motor, like a PLC with an analog output card, can be used.
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**Key Benefits of Torque Motors**
- **Simple Configuration:** Unlike servo systems, torque motors do not require complex setups involving feedback loops or sensors. Simply controlling the voltage input suffices.
- **Avoids Slack:** Tension is crucial to preventing slack in materials being wound or unwound. Torque motors excel in this regard by maintaining consistent tension regardless of changes in diameter.
- **Fine Adjustment for Proper Tension:** A torque motor can serve as an unwinding brake, generating braking force when rotated in the opposite direction to the winding motor. This feature ensures appropriate tension during winding processes without requiring frequent brake maintenance.
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Applications for torque motors extend beyond just winding operations. They can also be utilized in pushing/rejecting mechanisms and screw tightening tasks.
Check out this video demonstration showcasing the functionality of a torque motor:
In the video, you’ll notice that one motor maintains constant tension while the other exhibits noticeable slack. This comparison highlights the efficiency of torque motors in tension management.
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If you're looking for a more advanced solution than what torque motors offer, consider options like AC motors, brushless motors, AlphaStep motors, or servo motors. Each comes with varying levels of torque control accuracy and total costs:
| Feature | AC Motors & Torque Motors | Brushless Motors (BXII Series) | AlphaStep (AR/AZ Series) | Servo Motors (NX Series) |
|------------------------|---------------------------|--------------------------------|--------------------------|--------------------------|
| **Torque Control Accuracy** | ±10% | ±10% | AR: ±10%, AZ: ±20% | ±5% |
| **Total Cost** | Low | Moderate | Moderate | High |
For example, the NX Series boasts excellent repeatability, achieving ±0.23% precision (as per reference values).
Ultimately, selecting the right motor for tension control hinges on your specific requirements regarding torque accuracy and budget considerations.
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If you'd like to delve deeper into sizing a torque motor or exploring these alternatives further, feel free to reach out!
Water Chiller
Water chiller, either water cooled, or air cooled, is to provide chilling water through a refrigerant phase change. Essential components are compressor, condenser, expansion valve, evaporator, and relevant parts. Water chillers are typically used in industrial and commercial applications such as air conditioning, refrigeration, and process cooling. They are also used in residential applications such as air conditioning system. Water chillers are available in a variety of sizes and configurations to meet the needs of different applications.
For water cooling type water chillers, they can be installed in mechanical rooms or basements for space saving purpose. Air cooling type, on the other hand, is mostly considered to be suitable for outdoor conditions in order to attain better ventilation.
In particular, screw-type low-temperature chillers are used in production processes that require low-temperature treatment such as freezing, refrigeration, and industrial cooling. The product models are complete, which can meet the use places with different cooling capacity and temperature requirements.
The unit is mostly used in industrial and commercial cooling systems for food processing, pharmaceuticals, refrigeration and various special low temperature requirements.
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