RS7 Series Instruction Manual - Benshaw

GENERAL
Benshaw RS7 Series Solid State Reduced Voltage Starters are used for three-phase squirrel cage,
wound rotor, and synchronous induction motors, The RS7 Starter has an adjustable starting iorque
followed by an adjustable voltage ramp with stopping brake torque and brake time adjustments. The
starting torque and voltage ramp adjustments enable smooth motor acceleration to full speed, providing a
soft start, and allowing for full starting torque if and when required. The stopping brake torque and brake
time adjustments enable smooth motor deceleration to zero speed providing controlled stopping times. This
adjustment procedure reduces hazards associated with coasting machinery, overhauling loads, etc.
In cases where load and motor conditions cause instability near the end of the acceleration ramp, an
accel kicks circuit can be adjusted to provide a quick step-up to full motor voltage. The point at which the
step-up occurs can be adjusted from 50% to 100% of the accel ramp.
The RS7 Starter contains seven SCRs--six in a full-wave power circuit, and one as a gated free
wheeling diode. The power circuit is designed to provide maximum torque per ampere to eliminate the
potentially damaging DC voltage produced by a three SCR/three diode starter.
Benshaw RS7 Starters are constructed to permit rapid repair and replacement if required; ensuring
minimum downtime in the unlikely event a failure should occur.
DC INJECTION BRAKING SPECIFiCATION
•Starter Type: AC voltage controlled acceleration
DC voltage controlled braking
“Adjustments: Starting torque: 0% to 100% rated motor torque
Ramp time to full motor voltage: 0.5 seconds to 60 seconds
Accel kick: 50% to 100% of rated motor voltage
Jog at set speed: 0% to 100% rated input voltage
Variable Torque: 0% to 100% rated motor torque.
Brake torque: 0% to 50% rated motor torque
Brake time: L5 seconds to 30 seconds
“Control: Start/stop: Two or three wire--either internal 24VDC (dry contact) or external
12OVAC control power
Jog at Set Speed Control: Momentary jog pushbutton with one (1) set N/C, N/C,
form C contacts either internal 24VDC or external 12OVAC control power
Auxiliary Contact Available: Up to four (4) sets, N/C, N/C, form C jog contacts. (but
no more than a total of 4 sets for form contacts)
PRE-STARTIJP INSPECTION
Ciean out a metalic particles and foreign matter.
2. Check all connections for tightness. Use recommended procedure for aluminum conductors.
3. On high resistance ohmmeter scale, check Li to Ti, T2, T3. Repeat for L2, L3 Check all terminals to
ground. All readings should be several megohms or more.