This document describes the Boston Gear BETA II Single-Phase Adjustable-Speed DC Motor Controllers, which are designed for industrial and commercial motor control applications. These controllers are Underwriters Laboratories Listed (File No. E60207) and CUL approved (File No. LR19781).
Function Description
The BETA II controllers are designed to regulate the DC power to nonregenerative, adjustable-speed armature control of shunt-wound and permanent-magnet motors. They provide a means to control the speed, direction, and stopping of DC motors. The controllers offer various operational modes, including Run-Stop-Jog, Forward-Reverse, Pushbuttons and Run-Jog, Unidirectional Armature Contactor, Armature Contactor Reversing, and Line Starting with Motor Speed Potentiometer. They also support external speed and torque reference signals.
Important Technical Specifications
The BETA II controllers are available in several models: RBA2C, RBA2CU, RBA2CM, and RBA2CN.
- Power Source: Single-phase, 50 or 60 Hz.
- 115V, 50 or 60 Hz: Output VDC Armature 0-90V, Field 50/100V. Speed Reference Signal 0-10VDC. Magnetic Control Voltage 24VDC.
- 230V, 50 or 60 Hz: Output VDC Armature 0-180V, Field 100/200V. Speed Reference Signal 0-10VDC. Magnetic Control Voltage 24VDC.
- Horsepower Range: 1/6 - 2 HP (continuous duty).
- Line Fuse Interrupting Capacity: 100,000 Amperes.
- Motor Speed Potentiometer: 5K Ohms, 1/2W.
- Overload Capacity, Armature Circuit: 150% For 1 Minute.
- Service Factor: 1.0.
- Controller Weights:
- RBA2C: 0.9 lbs (0.41 kg)
- RBA2CU: 1.7 lbs (0.77 kg)
- RBA2CM: 1.7 lbs (0.77 kg)
- Operating Conditions:
- Altitude: 1000 Meters (3300 Feet) Maximum.
- Ambient Temperature: 0 - 55°C (32°F - 131°F).
- Line Frequency Variation: ± 2 Hz Of Rated.
- Line Voltage Variation: ±10% Of Rated.
- Relative Humidity: 95% Noncondensing.
- Performance Characteristics:
- Controlled Speed Range: 0 To Motor Base Speed.
- Displacement Power Factor (Rated Speed/Rated Load): 87%.
- Efficiency (Rated Speed/Rated Load):
- Controller Only: 98%.
- Controller With Motor, Typical: 85%.
- Speed Regulation Characteristics:
- Standard Voltage Feedback with IR Compensation: Load Change (±10%) 2%, Line Voltage (±10%) ±1%, Field Heating (Cold/Normal) 5-12%, Temperature (±10°C) ±2%, Speed Rating 50:1.
- Optional Speed (Tach) Feedback: Load Change (±10%) 0.5%, Line Voltage (±10%) ±1%, Field Heating (Cold/Normal) 0.2%, Temperature (±10°C) ±2%, Speed Rating 200:1.
- Note: Unidirectional models only.
- Dynamic Braking: The controller provides dynamic braking to stop the motor. The braking torque varies with horsepower and can be adjusted.
- 1/6 HP: 115V (180 ft-lb), 230V (NA).
- 1/4 HP: 115V (129 ft-lb), 230V (NA).
- 1/3 HP: 115V (103 ft-lb), 230V (NA).
- 1/2 HP: 115V (66 ft-lb), 230V (NA).
- 3/4 HP: 115V (44 ft-lb), 230V (278 ft-lb).
- 1 HP: 115V (34 ft-lb), 230V (190 ft-lb).
- 1-1/2 HP: 115V (12.4 ft-lb), 230V (130 ft-lb).
- 2 HP: 115V (NA), 230V (88 ft-lb).
- Shunt Field Data:
- 115V: Half-Wave 50, Full-Wave 100.
- 230V: Half-Wave 100, Full-Wave 200.
- Motor Shunt Field Lead Connections: F1, F2, F+, F-.
Usage Features
- Installation: The controllers can be surface-mounted vertically. Multiple controllers can be mounted side by side, but allow at least 2 inches (5.08 cm) between controllers for cooling efficiency.
- Wiring: The document provides detailed wiring diagrams for various operational modes, including Run-Stop-Jog, Forward-Reverse, Pushbuttons and Run-Jog, Unidirectional Armature Contactor, Armature Contactor Reversing, and Line Starting with Motor Speed Potentiometer.
- Potentiometer Settings: The controller has several potentiometers for adjustment:
- ACCEL (Acceleration): 2/3 Turn Clockwise for 10 Seconds.
- CUR LMT (Current Limit): Fully Clockwise (100%) for 150% Load.
- DECEL (Deceleration): 2/3 Turn Clockwise for 10 Seconds.
- IR/COMP (IR Compensation): Fully Counterclockwise (0%) for 0% Boost.
- MAX SPD (Maximum Speed): 3/4 Turn Clockwise for 100% Speed.
- MIN SPD (Minimum Speed): Fully Counterclockwise (0%) for 0% Speed.
- Run-Stop-Jog Operation: A RUN-STOP-JOG switch is used to place the switch in RUN position. Otherwise, initiate a Run command. A Run command will accelerate the motor to the setting of the MOTOR SPEED potentiometer or external speed reference signal, as applicable. The rate of acceleration is preset by the ACCEL potentiometer on the controller control board.
- Speed Control: Motor speed is directly proportional to the setting of the MOTOR SPEED potentiometer or the magnitude of an external speed reference signal. Maximum speed is preset by the MAX SPD and MIN SPD potentiometers.
- Reverse Operation: To reverse motor rotation on controllers with reversing capabilities, initiate a Stop function and then initiate a reversing command. The motor will then accelerate to the setting of the MOTOR Speed potentiometer or external speed reference signal, as applicable.
- Tachometer Feedback: The controller supports tachometer feedback for improved speed regulation. Jumpers J2 and W4 are used to select the tachometer generator voltage at maximum speed.
- Torque Control: An external 5K ohm Current (Torque) Limit potentiometer can be used as shown in Figure 12 on page 11. Jumper W6 must be removed from the controller control board if an external Current (Torque) Limit potentiometer is desired.
- External Speed Reference: The controller can accept a 0-10 VDC external speed reference signal.
Maintenance Features
- General Maintenance: Keep the controller dry and free of dust, dirt, and debris. No parts require periodic replacement. Periodically turn-off the AC line supply to the controller and check all wire terminations to be sure they are tight. Visually check components for damage due to overheating or breakage. All damaged and/or faulty components must be replaced for satisfactory operation. Maintain the motor according to maintenance instructions supplied by the motor manufacturer.
- Troubleshooting: The manual provides an extensive troubleshooting guide with possible causes and corrective actions for various issues, including:
- AC line open: Be sure rated AC line voltage is applied to the controller.
- Operator controls inoperative or connected incorrectly: Repair accordingly.
- Open circuit between Connectors E1 and E2: A wire jumper or switch must connect E1 to E2.
- Controller not reset: Initiate a Stop command and then a Start command.
- Line Voltage Selection Jumper J1 in wrong position: See Step 4 on page 5 under, "Installing The Controller."
- Controller not enabled: Be sure +24 VDC is applied to Terminal TB2-8.
- Loss of speed reference signal: Check for 0 - 10 VDC speed reference signal.
- Controller not adjusted correctly: Turn the ACCEL and CUR LMT potentiometers fully clockwise (100%).
- Open shunt field winding or wiring to the motor shunt field, causing loss of torque: Check the motor shunt field and associated circuitry for a loose connection or a broken wire. Repair accordingly.
- Motor failure: Repair or replace the motor.
- Control board failure: Replace the control board.
- Wiring faulty or incorrect: Check all external wiring terminating in the controller. Correct accordingly.
- Circuit, component, or wiring grounded: Remove ground fault.
- SCR1 and SCR2 shorted: Replace shorted SCR’s or the control board.
- Bridge Diode D2 or D3 shorted: Replace shorted diode or the control board.
- Varistor RV1 shorted: Replace RV1 or the control board.
- Shunt Field Diode D4 or D5 shorted: Replace shorted diode or the control board.
- Motor shunt field shorted or grounded: Repair or replace the motor.
- Motor overloaded: Check shunt field current. Low shunt field current causes excessive armature current. If field current is adequate, check for a mechanical overload. If the unloaded motor shaft does not rotate freely, check motor bearings. Also check for a shorted motor armature. Motor overload can also be caused by incorrect gear ratio. Correct accordingly.
- Loose or corroded connection. Wiring faulty, incorrect, or grounded: Check all terminals, connections, and wiring between the line, operator controls, controller, and motor.
- Minimum speed not adjusted correctly: Turn the MIN SPD potentiometer counter-clockwise.
- Motor armature grounded: Correct ground fault.
- Maximum speed set too high: Turn the MAX SPD potentiometer counter-clockwise.
- Controller not calibrated correctly: Refer to Steps 3 and 4 on page 5.
- Motor field demagnetized: Replace the motor.
- Low line voltage: Check for rated line voltage, ±10%, on the controller line terminals.
- AC line voltage fluctuating: Observe line voltage with a voltmeter or oscilloscope. If fluctuations occur, correct condition accordingly.
- Oscillating load connected to the motor: Stabilize the load. Turning the IR/COMP potentiometer counterclockwise may minimize oscillations.
- Voltage Selection Jumpers J1 and J2 in wrong position: See Step 4 on page 5 under, "Installing The Controller."
- IR compensation not adjusted correctly: See the IR Compensation adjustment instructions on page 17.
- Maximum speed not adjusted correctly: See the Maximum Speed adjustment instructions on page 18.
- Motor faulty: Check motor brushes. Replace if needed. Repair or replace the motor.
- Tachometer generator or coupling faulty (if used): Repair accordingly.
- Shunt field current too low: Check motor rating and refer to Table 12 on page 28.
- Shunt field connected for incorrect voltage: Check motor rating and refer to Table 12 on page 28.
- Shunt field windings shorted: Measure the shunt field resistance and compare with the motor rating. Repair or replace the motor.
- Ventilation insufficient: Remove dirt, dust, and debris from the motor intake and exhaust screens.
- Excessive motor load at low speed: Reduce the load or increase the speed.
- Line and motor armature current excessive: See Indication 9.
- Motor overheating from friction: Check for misalignment. Realign the motor.
- Shorted motor windings or faulty bearings: Repair or replace the motor.
- Parts List: The manual includes a list of replaceable parts for RBA2C controllers, such as the Control Board, Diodes, Line Fuse, Relay K0, SCR1 & SCR2, Transformer T1, Varistor RV1, DB Resistor, Relays K1-K4, Relays K5 & K6, Reversing Board, and Transformer.
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