160 SSC Variable Speed Drives Selection Guide
Variable Speed Drives (VSDs), also referred to as Adjustable Speed Drives (ASDs), are electronic devices primarily used to control the motor speed and torque. They accomplish this by adjusting the characteristics of the motor’s power supply, thereby matching the motor’s torque and speed to the machine/process requirements.
A Variable Speed Drive functions by converting the fixed frequency, electrical supply input into a variable frequency output. This variation in frequency enables the VSD to control the operation of the connected motor – a higher frequency output for a faster motor speed and a lower frequency output for a slower motor speed. The output can also be adjusted to make the motor generate more or less output torque as required by the process. Hence, the combination of an electric motor and a VSD can be used to turn large loads at relatively slow speeds, or lighter loads at high speeds, consequently maximizing machine/process efficiency.
Most variable speed drive systems consist of three main elements: (i) Drive Controller, (ii) AC Motor, and (iii) Operator Interface. The operator interface provides a means for users to start and stop the AC motor and adjust the motor speed accordingly.
160 SSC Variable Speed Drives Overview
The 160 Smart Speed Controllers (SSC), Bulletin 160 “Series C”, are compact variable speed drives from Rockwell Automation, manufactured under the Allen-Bradley brand name. These speed drives are microprocessor controlled and can be programmed for diverse applications. They are mainly used to control three-phase AC induction motors.
Also, the Bulletin 160 “Series C” variable speed drives are enhanced with Sensorless Vector performance. Sensorless Vector Control (SVC) offers numerous benefits including, outstanding acceleration performance, improved torque performance, improved speed regulation using Slip Compensation, as well as tight control of both motor speed and current draw even with a varying load. In addition, this control method can be implemented as Flux Vector Control.
The innovative “Series C” design, a comprehensive range of power ratings (from 0.37kW (0.5 HP) to 4kW (5 HP)), improved hardware design, and increased functionality place the Bulletin 160 SSC drives on top-of-the-range for microdrives applications. Essentially, the Allen‑Bradley 160 SSC variable speed drives are well-suited for applications controlled by analog input signals. Examples of such applications are:
- Control of Fans & Pumps used in HVAC, Refrigeration, Clean Room (PI), Paint Booths, Vent Hoods, Injection, Slurry, Exhaust, and Metering applications,
- Controlling Machine Tools used in Milling Machines, Lathes, Drill Pressers, Saws, Woodworking, and Grinders.
Additionally, the Allen‑Bradley 160 SSC drives can also be an excellent solution in applications requiring several specific preset speeds, such applications include:
- Manufacturing and Material Handling – Feeders, Mixers, Conveyors, Palletizers, Winders, Trolleys, and Monorails.
- Commercial Applications – Automatic Car Washes, Laundry Machines, Dock Levelers, and Automatic Doors.
As well as in many other applications that use digital control inputs.
Features of the Bulletin 160 "Series C"
Before looking at the factors to consider when selecting a specific 160 SSC variable speed drive for a given application, let’s first discuss the general features of the Bulletin 160 “Series C”. It’s important to take into consideration some of these features when selecting a Bulletin 160 SSC drive from other Allen‑Bradley microdrives. The features include:
A) Hardware Drive Features
- Feed through Wiring: The Allen‑Bradley 160 SSC drives include 6-Pole feed-through power terminals which simplify power and ground wiring practices, making these drives an ideal solution for constant speed retrofits.
- Hinged Terminal Guards: These allow easy access to load/line power terminals because the terminal screws are easily removable for ring lug connections.
- Program Keypad Module: This module provides local control, and it also enables access to all display and program parameters. It can be a factory-installed option or be purchased separately and field installed.
- DIN Rail Latch or Attachable Panel: The latch permits quick, low-cost mounting of the Bulletin 160 SSC drives on standard 35mm DIN rail. However, this feature is unavailable with 1.5 kW or 4.0 kW single-phase drive units.
- Normally Open (N.O.)/Normally Closed (N.C.) Contact: It connects to the drive’s indicators/controls for monitoring specific load/drive conditions, allowing a programmable output.
- Programmable Terminal Block: It provides the flexibility of meeting the control requirements of various applications, without the need for an additional external control logic.
- Dynamic Brake Module: This is an optional drive feature, which allows users to connect dynamic brake resistors. It’s not available on 0.55kW (0.75 HP) and 0.37kW (0.5 HP) Bulletin 160 SSC speed drive ratings.
- Capacitor Module: This drive module is optional, and it enables users to connect a Bulletin 160 SSC speed drive to an external capacitor, for enhanced inherent braking performance and extended ride-through capability during a power loss.
- DC Bus Test Points: They provide quick access for digital multimeter or motor drive analyzer test probes when DC Bus Voltage is being measured.
- 24V DC Interface: This module enables users to command a Bulletin 160 SSC drive with 24V DC logic (sinking inputs). It is an optional module.
- Cooling Fan: It prevents overheating by providing airflow across the drive’s heatsink fins. It’s not necessary on 0.55kW (0.75 HP) and 0.37kW (0.5 HP) Bulletin 160 SSC drive ratings.
B) Available Control Models
The Bulletin 160 SSC variable speed drives are available with two control models, namely:
- Analog Signal Follower: This control model accepts a speed reference input from a remote potentiometer, 0-10V DC source, +/- 10V DC source, or 4-20 mA source. The Bulletin 160 SSC drives can thus be configured to accept different speed reference input signals and use various methods of Stop/Start/Direction control.
- Preset Speed Control model: This is a 2 Wire Run Forward/Run Reverse control method. In Bulletin 160 SSC drives, the Preset Speed control model is capable of eight (8) independent preset speeds and two (2) speed-dependent acceleration/deceleration ramp times. While the speed reference for this model is selected with three digital control inputs.
C) Supported Communication Modules
Control and monitoring of Bulletin 160 SSC drive parameters can be done via the following optional communication modules:
- DeviceNet Module (Catalog No. 160-DN2)
- RS-232 Serial Module (Catalog No. 160-RS1)
- Profibus Module (Catalog No. 160-PD1)
- Interbus Module (Catalog No. 160-IB1)
D) Operator Interface Options
There are four different Bulletin 160 SSC operator interface devices. Each Bulletin 160 SSC variable speed drive is available with one of the four. The four operator interface options are:
- Ready/Fault Indicator Panel (Catalog No. 160-B1): This control panel indicates whether the Bulletin 160 SSC drive is “READY” for control operation or if a “FAULTY” drive condition is present. It’s provided as a standard control module when there’s no other factory-installed operator interface option. It is an ideal low-cost control solution for applications that don’t require parameter monitoring and where parameter adjustments are not necessary.
- Program Keypad (Catalog No. 160-P1): This interface enables the operator to monitor and/or modify the drive parameters of a Bulletin 160 SSC drive. It also provides a local keypad control with Start, Reverse, and Stop functions. It can be factory installed or purchased separately. The module also reports the drive status, input status, and specific fault codes; this information is useful when performing drive diagnostics and troubleshooting.
- Remote Keypad (Catalog No. 160-P2): This is a remotely mounted operator interface used in place of separate, panel-attached drive control inputs to minimize required control wiring and reduce installation time. It is designed to meet NEMA Type 4(IP65) environmental specifications.
- CopyCat Keypad (Catalog No. 160-P3): This is a hand-held programming operator interface that provides the ability to program and monitor individual Bulletin 160 SSC drive parameters. Also, using this interface all Bulletin 160 SSC drive parameters can be downloaded and uploaded, saving installation time while ensuring an accurate, repeatable drive setup.
Note: Both Remote Keypad and CopyCat Keypad modules require a Remote Programming Adapter (Catalog No. 160-RPA) and an appropriate cable. The 160-RPA adapter provides a simple interface for the two operator interface modules.
E) Compliance Certifications
Available Bulletin 160 SSC variable speed drives are compliant with the following standards:
- cUL: UL 508C (Canada and U.S.)
- CE EMC: EN61800-3 (Europe)
- CE Low Voltage: EN60204-1 (Europe)
- C-Tick: AS/NZS2064.1 (Australia)
Selection Guidelines
Variable Speed Drives produce harmonics that can negatively affect the performance of the AC motor being controlled and the efficiency of the supply voltage. It is therefore necessary to select a VSD that will best match your application requirements. Outlined below are some of the key factors you should consider to make sure that you specify the right Bulletin 160 SSC variable speed drive for your specific application.
1. Required Horsepower
While it is important to determine the size of your variable speed drive concerning the electric motor it’s intended to control, working out the horsepower of the load being driven is also vital when choosing the proper Bulletin 160 SSC VSD for your application. From there, you can then consider other factors to help further narrow down your options.
2. Voltage Class
Depending on the voltage range of your application, you can select a Low-voltage class or a High-voltage class variable speed drive. Bulletin 160 SSC adjustable speed drives are designed for low-voltage motor control applications, ranging from 200…460V. These drives are available in three classes of input voltage, with each voltage class having different power and current (amp) ratings.
Note: If the electrical supply to the adjustable speed drive is single-phase power, ensure that you select an Allen‑Bradley 160 SSC drive with single-phase ratings, and similarly if it’s three-phase power.
3. Type of Load
Variable speed drives are commonly used with two types of loads: Constant Torque (CT) and Variable Torque (VT). There are distinct drive ratings for each load type. Therefore, you should determine whether your Bulletin 160 SSC drive application requires a variable torque or constant torque because the drive’s operating parameters are systematized accordingly.
For example, when the machine being driven is a centrifugal fan or pump, then a variable torque Bulletin 160 SSC drive will be a better option because it offers appreciable energy savings required in such applications. For conveyors and general-purpose machine control, use constant torque Bulletin 160 SSC drives. If you’re not sure whether to use CT or VT ratings, it’s recommended that you select a constant torque drive.
4. Full Load Amperage
Full Load Amperage (FLA) is defined as the maximum amount of current that an electric motor can draw when providing the rated output – it’s simply the rated current of the connected motor for a particular horsepower (rated load and voltage conditions). FLA is one of the most critical factors you should consider when choosing a variable speed drive, to ensure that the drive you select can handle the current strains of the AC motor being controlled.
To appropriately use this metric for Bulletin 160 SSC drive selection, check the full load current rating of the motor to be controlled, then find a Bulletin 160 SSC variable speed drive whose amp ratings can handle that much current. It’s recommended that you select a variable speed drive with a higher Full Load Amperage rating than that of the connected motor despite the initial cost because, in the long run, it will eventually pay off in terms of performance and reliability.
5. Overload Capacity
Make sure that you select a Bulletin 160 SSC drive that can grip any overload conditions which may occur during motor startup or due to erratic extra loading. Many VSD applications experience transitional overload conditions due to the power requirements of starting heavy-duty motors or as a result of excessive loading, and in such cases, you may be required to upsize your Bulletin 160 SSC drive.
Most variable speed drives are designed to activate overload protection at 150% overload condition for only 60 seconds. However, if your application requires an overload capacity higher than 150% or for more than 60 seconds, then you should oversize the Bulletin 160 SSC drive you’re considering.
6. Duty Cycle
Selecting the correct Bulletin 160 SSC drive for your application also depends on whether the load being driven is varying, steady, includes pulsating torques, or if it follows a repetitive load variation cycle. Duty cycle, also known as duty factor, can be defined as a constant repetitive pattern of the connected load over a specific duration of time; it’s expressed as the ratio of the time the load is ON (on-time) to the time the load is OFF (cycle period). This metric should particularly be taken into consideration if the application would require the VSD to idle or operate at a reduced load than rated for more than 25% of the time.
Bulletin 160 SSC variable speed drives feature a Programmable Duty Cycle to meet a great variety of braking applications. Also, with these drives, you can include a Dynamic Brake optional module, which allows external dynamic braking for motor control applications having a duty cycle of less than 5%. For applications whose duty cycle exceeds 5%, you should properly size the resistor package of your Bulletin 160 SSC drive to prevent overheating.
7. Environmental Specifications
Environmental conditions such as relative humidity, ambient temperature, storage temperature, altitude, supply of cooling air, acceptable levels of vibration and mechanical shock, as well as the presence of moisture, dust, gas, and other contaminants, should all be taken into consideration when selecting a Bulletin 160 SSC variable speed drive, its protective features, and enclosures.
Bulletin 160 SSC variable speed drives are available with different environmental ratings, including:
- IP20 Rated Drives: These Bulletin 160 SSC drives are characterized by an Open Style design with an attachable DIN rail, attachable control panel, feed-through power wiring, and compact package size.
- IP20 Rated Drives: These are Chassis Mounted Bulletin 160 SSC drives with an externally attached heatsink design. This design lowers the overall power dissipation of the variable speed drive by about 75% in comparison with the Open Style design. Also, the heatsink assembly is fitted with a gasket to meet IP66 (NEMA Type 4X or 4/12) environmental ratings and should be installed in a protective enclosure of similar ratings.
- IP66 Configured Drives: These can also be NEMA Type 4X and 4/12 Configured Bulletin 160 SSC drives. They include various IP66 (NEMA Type 4X and 4/12) rated components such as selector switches, pilot lights, fused disconnects, and DeviceNet communication modules.
8. Speed Range and Acceleration Time
The maximum and minimum motor speeds for your application will determine the base speed of the Allen‑Bradley 160 SSC drive you should select.
You should also consider the required acceleration time for your application. This is because acceleration time is inversely proportional to the available torque and directly proportional to the total inertia.