Data Bulletin. Applying the Altivar 61 AC Drive in Constant Torque Applications. Introduction

Transcription

1 Data Bulletin 88DB126 Applying the Altivar 61 AC Drive in Constant Torque Applications Retain for future use. Introduction Definitions: Variable Torque and Constant Torque; Normal Duty and Heavy Duty The Altivar 61 AC drive s variable torque capabilities provides an end user with an easy-to-use, robust product that delivers energy savings in a variety of centrifugal pump and fan applications. What is lesser known is this drive s capabilities in normal duty, constant torque applications. This paper provides guidance on the constant torque applications the ATV 61 drive is best suited to, thereby combining suitable performance with a cost-effective solution. The AC drive industry has traditionally identified applications as either variable torque or constant torque. In variable torque applications, motor load changes with the square of the speed and horsepower changes with the cube of the speed. Variable torque applications include centrifugal pumps and fans. Figure 1: Variable Torque 1 % 75 % 5 % Torque 25 % Horsepower 15 Hz 3 Hz 45 Hz 6 Hz Hertz Most other AC drive applications have conventionally been defined as constant torque. In this application, motor load is not a function of speed; as speed changes, load torque remains constant and horsepower changes linearly. Constant torque applications include: augers, some compressors, conveyers, hoists, mixers, and positive displacement pumps. Figure 2: Constant Torque 1 % 75 % Torque 5 % Horsepower 25 % 15 Hz 3 Hz 45 Hz 6 Hz Hertz 212 Schneider Electric All Rights Reserved

2 Applying the Altivar 61 AC Drive in Constant Torque Applications 88DB126 Importance of Torque Requirements AC drive manufacturers normally produce two types of drives: Drives able to provide up to 15% of transient current for constant torque applications Drives able to provide up to 12% of transient current for variable torque applications. Transient current is the percent of the nominal drive current rating that can be supplied for up to one minute. Today, for an increasing number of constant torque applications, an AC drive rated at 15% of transient current is not required for starting and operating the load connected to the motor. In some instances, excessive torque may damage connected equipment. The terms normal duty and heavy duty have been introduced to describe two different groups of constant torque applications: Normal duty typically refers to applications that require less than 12% of transient current and do not run continuously below 5 Hz. Heavy duty typically refers to applications that require up to 15% of transient current and operation below 5 Hz may be needed. Importance of Torque Requirements Hardware Comparison of the Altivar 61 and Altivar 71 Drives Understanding the starting-torque requirements, over-torque requirements, and the operational speed of the application are all important factors in selecting and providing the most cost-effective solution for the end user. There are a significant number of applications where the ATV 61 drive is a more cost-effective solution than the ATV 71 drive or a competitive AC drive. The ATV 61 and 71 drives are widely recognized for robust ratings and performance. Use comparisons in this data bulletin to understand the constant torque applications where the ATV 61 drive can be applied. Lower horsepower ATV 61 and ATV 71 drives are built with a common power platform and are dimensionally equal for any given horsepower rating. The following table provides the transient current and ambient temperature ratings for the lower horsepower range: Table 1: Lower Horsepower Range ATV 61 ATV 71 28/24 Vac 1/2 to 6 HP 4/48 Vac 1 to 1 HP 5/69 Vac 3 to 1 HP 28/24 Vac 1/2 to 6 HP 4/48 Vac 1 to 1 HP Transient Current Rating, 6 sec 12% 12% 12% 15% 15% 15% Ambient Temperature Rating 5 o C 5 o C 5 o C 5 o C 5 o C 5 o C 5/69 Vac 2 to 1 HP In the higher horsepower range, the ATV 61 hardware design, power components, and frame sizes are optimized for normal duty and variable torque applications. The following table provides the transient current and ambient temperature ratings for the higher horsepower range: Table 2: Higher Horsepower Range ATV 61 ATV 71 28/24 Vac 75 to 125 HP 4/48 Vac 125 to 9 HP 5/69 Vac 125 to 8 HP 28/24 Vac 75 to 1 HP 4/48 Vac 125 to 7 HP Transient Current Rating, 6 sec 11% 11% 11% 15% 15% 15% Ambient Temperature Rating 45 o C 45 o C 45 o C 5 o C 5 o C 5 o C 5/69 Vac 125 to 7 HP Schneider Electric All Rights Reserved

3 88DB126 Applying the Altivar 61 AC Drive in Constant Torque Applications 12/212 Functionality Supported by Altivar 71 Drive Firmware Functionality Supported by Altivar 71 Drive Firmware Altivar 61 Drive Performance ATV 61 and ATV 71 drives have different firmware. The ATV 71 drive has functionality for high-end applications that is not found in the ATV 61 drive, including: Hoisting functions Mechanical brake closing functionality Positioning by sensor functionality Torque control Limit switch input functionality Master-slave functionality ENA functionality Sensorless Vector Control, current mode (labeled SVCI in the firmware) Closed Loop Vector Control (labeled FVC in the firmware) If your application requires this functionality, select the ATV 71 drive. The ATV 61 drive ships from the factory configured for the Volts/Hz motorcontrol type, while the ATV 71 drive ships configured for the Sensorless Vector Control voltage mode motor-control type. The ATV 61 drive provides the ability to enable the same Sensorless Vector Control voltage mode (labeled SVCV in the firmware) motor-control algorithm found in the ATV 71 drive. Selecting SVCV motor-control type for the ATV 61 drive improves its starting torque, accelerating torque, and dynamic speed performance. The SVCV motor-control algorithm uses motor modeling, speed reference, real-time current feedback, and input voltage to control the orientation and magnitude (vector) of the motor s magnetic field. This capability enables separate control of magnetizing current and torque-producing current and provides enhanced motor torque characteristics throughout the speed range. While the ATV 71 drive s low-speed motor performance is superior to the ATV 61 drive s, the speed torque curve in Figures 3 and 4 details typical starting torque characteristics of the ATV 61 drive range with SVCV motorcontrol selected and an autotune performed at set-up. The speed torque curve in Figures 5 and 6 details typical motor breakdown torque characteristics using the ATV 61 drive. The charts in this document demonstrate that the ATV 61 range of AC drives can be applied to applications that require up to 13% of nominal motor torque at startup or during operation for up to one minute. Performance data in the figures was generated using a 15 HP ATV61HD11N4 AC drive and a 15 HP motor, rated for 18.8 amps at full load, with a nominal torque rating of 59.3 N m. 212 Schneider Electric All Rights Reserved 3

4 Applying the Altivar 61 AC Drive in Constant Torque Applications 88DB126 Altivar 61 Drive Performance Figure 3 shows the ATV 61 drive successfully accelerating a loaded motor from to 6 Hz with the acceleration time set at 3 seconds. To demonstrate the capability of the drive, current limit was set at maximum and the motor was loaded to 138% of nominal motor torque. In this example, the drive produced a starting torque of 19% of nominal motor torque briefly while accelerating the load of 138% of the nominal torque to 6 Hz. Figure 3: Speed Torque Curve: to 6 Hz, Fully-loaded Motor 19% 138% 1% Motor Speed 6 Hz Hz Motor Speed Time (sec) 3.6 Figure 4 shows the ATV 61 drive successfully accelerating a fully loaded motor from to 5 Hz with the acceleration time set at 3 seconds. To demonstrate the capability of the drive, current limit was set at maximum and the motor was loaded to 141% of nominal motor torque. In this example, the drive produced a starting torque of 17% of nominal motor torque briefly while accelerating the load 141% of the nominal torque to 5 Hz. Figure 4: Speed Torque Curve: to 5 Hz, Fully-loaded Motor 17% 141% 1% Motor Speed 5 Hz Hz Motor Speed Time (sec) Schneider Electric All Rights Reserved

5 88DB126 Applying the Altivar 61 AC Drive in Constant Torque Applications 12/212 Altivar 61 Drive Performance Figure 5 shows the Altivar 61 drive operating at 6 Hz, with an increasing load applied to determine motor breakdown torque. To demonstrate the capability of the drive, current limit was set at maximum. In this example, the drive produced a breakdown torque of 158% of the nominal motor torque before the motor stalled. Figure 5: Speed Torque Curve: Break Down Torque at 6 Hz 158% 1% Motor Speed (r/min) Figure 6 shows the Altivar 61 drive operating at 5 Hz, with an increasing load applied to determine motor breakdown torque. To demonstrate the capability of the drive, current limit was set at maximum. In this example, the drive produced a breakdown torque of 2% of the nominal motor torque before the motor stalled. Figure 6: Speed Torque Curve: Break Down Torque at 5 Hz 2% 1% Motor Speed (r/min) Schneider Electric All Rights Reserved 5

6 Applying the Altivar 61 AC Drive in Constant Torque Applications 88DB126 Recommended Applications for Altivar 61 Drives Recommended Applications for Altivar 61 Drives Other Considerations Summary In addition to industrial centrifugal pump and fan applications, the ATV 61 drive can be applied in many normal duty constant torque applications that do not require starting motor torque or transient motor torque above 13% and do not require continuous low speed operation below 5 Hz. More OEMs are constructing machines that do not require a drive that can produce heavy-duty over torque. The following are excellent candidate applications to investigate where the ATV 61 drive is the most cost-effective solution: Compressors Conveyers Extruders Machine tools Mixers Positive displacement pumps Rotary blowers Selecting the SVCV motor control type, entering the motor nameplate data, and performing an autotune when starting up the drive is required to obtain the best motor performance. Starting torque requirements depend on several factors determined by the application, including: Allowable starting time Minimum operating speed Rotating inertia Material viscosity Inertia that needs to be overcome to start the load moving Pressure in a system that needs to be overcome to start Working closely with the equipment user or OEM can ensure a robust, costeffective installation. The horsepower information presented in this document relates to the ATV 61 drive and ATV 71 drive product ranges. Do not apply the information in this document to ATV 61 drive products packaged in E-Flex, M-Flex, Powergard, and Motor Control Center (MCC) enclosures. The ratings of these ATV 61 drive products have already been optimized. The ATV 61 drive is an excellent choice for many industrial centrifugal pump and fan applications, providing end users with an easy-to-use, customizable, robust product that delivers energy savings. In addition, following the guidelines detailed in this document allows the ATV 61 drive to be a costeffective solution in applications that are referred to as normal duty, constant torque applications. Select the drive based on the incoming voltage and the motor full-load current rating on the name plate of the motor. Understanding the motor speed range, starting torque requirements, and expected transient motor torque performance are the key points to follow in selecting the proper Altivar drive for the application Schneider Electric All Rights Reserved

7 88DB126 Applying the Altivar 61 AC Drive in Constant Torque Applications 12/212 Summary 212 Schneider Electric All Rights Reserved 7

8 Applying the Altivar 61 AC Drive in Constant Torque Applications 88DB126 Data Bulletin Schneider Electric USA, Inc. 81 Knightdale Boulevard Knightdale, NC Electrical equipment should be installed, operated, serviced, and maintained only by qualified personnel. No responsibility is assumed by Schneider Electric for any consequences arising out of the use of this material. Square D and Schneider Electric are trademarks or registered trademarks of Schneider Electric. Other trademarks used herein are the property of their respective owners Schneider Electric All Rights Reserved