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MN704
Chapter 1
Introduction
Introduction
Thank you for purchasing the BC141, BC142, BC142-5 or BC142-6 full-wave variable speed DC motor
control. The control, with Surface Mount (SMT) construction, offers the user the ultimate in reliability
and performance at an affordable price. The controls contain a unique patented super-fast Direct-
Fed™ current limit circuit that protects the SCR power bridge against direct shorts1. The reliability of
the control is further enhanced with the use of high-surge, 25 Amp SCRs, and AC line and armature
fusing2,3. The control is designed with exclusive Plug-In Horsepower Resistor® 3, which eliminates
the need for recalibrating IR Comp and Current Limit when the control is used on various horsepower
motors. In addition, the rating of the control can be extended to 1.5 HP for controls with 90 Volt DC
output and 3 HP for controls with 180 Volt DC output, by the use of an Auxiliary Heat Sink4. Catalog
Nos. BC142, BC142-5 and BC142-6 also allow operation of 90 Volt DC motors when used on 208/230
Volt AC line input5.
The versatility of the control is confirmed by its extensive list of standard features, such as: selectable
armature or tach feedback and adjustment trimpots for minimum speed, maximum speed, current
limit, IR compensation, and linear acceleration and deceleration. The control includes Auto-Inhibit®,
which eliminates surging during rapid AC line switching; pulse transformer triggering, which provides
cogless operation at low speed; and superior noise rejection circuitry, which eliminates false starts
and blown SCRs. Enable (normally closed) and Inhibit (normally open) functions provide electronic
switching of control output.
The output voltage of the control is a linear function of the Main Speed Potentiometer setting. In
addition, the control can be used in a voltage following mode by supplying an isolated analog input
signal to Terminals P2 (+) and P1 (-). The control is compact in size (only 4.30 X 3.64 X 1.25) and
easily replaces all competitive speed controls. The control is supplied with a factory installed 25 Amp
AC line fuse, a 5 kΩ Main Speed Potentiometer and QD terminals. All models are UL Listed (USA and
Canada) and CE Approved.
SAFETY NOTICE
A Warning statement indicates a potentially hazardous situation which, if not avoided, could result in
injury or death.
A Caution statement indicates a potentially hazardous situation which, if not avoided, could result in
damage to property.
A Note indicates additional information that is not critical to the installation or operation.
WARNING: This equipment may contain voltages as high as 1000 volts! Electrical shock can cause serious or fatal
injury. Only qualified personnel should attempt the start-up procedure or troubleshoot this equipment.
WARNING: Be sure the system is properly grounded before applying power. Do not apply AC power before you
ensure that all grounding instructions have been followed. Electrical shock can cause serious or fatal
injury.
WARNING: Electrical shock can cause serious or fatal injury. Be sure that all power is disconnected and there is
no voltage present from this equipment or equipment to which it is or will be connected. Electrical
shock can cause serious or fatal injury. Only qualified personnel should attempt the installation and
start-up procedures.
WARNING: Electrical shock can cause serious or fatal injury. Verify there is no voltage phase-to-phase or phase-
to-neutral at the motor leads before connecting motor to this control. Motor may have high voltage
present even when disconnected from this control.
WARNING: Do not use motor overload relays with an automatic reset feature. These are dangerous since the
process may injure someone if a sudden or unexpected automatic restart occurs. If manual reset
relays are not available, disable the automatic restart feature using external control wiring.
WARNING: This unit has an automatic restart feature that will start the motor whenever input power is applied
and a RUN (FWD or REV) command is issued. If an automatic restart of the motor could cause injury to
personnel, the automatic restart feature should be disabled.
WARNING: Using a jumper to eliminate the start/stop function will cause the motor to run at the Main Speed
Potentiometer setting when the AC line is applied.
