PSC Motor Speed Control

The 770-PSC Control offers a way to add existing single phase PSC or shaded pole motor fans to a building automation system. The 770-PSC control measures the motor's RPM, using an easy to attach sensor, and can adjust the motor's speed to match a chosen set point. The control can be operated locally using the 32 character LCD display and pushbuttons, or it can be operated over a Modbus RTU connection.

There are two modes of motor speed control available. In manual mode (open loop), the control provides a fixed power level to the motor indicated by a Speed Index ranging from 0 to 100%. The actual motor rpm will vary with changes in loading. In automatic mode (closed loop), the control uses a PI feedback algorithm to drive the sensed motor rpm to match an rpm set point (300 rpm minimum).

The 770-PSC is normally used to set and maintain the speed of PSC or shaded-pole motors between a selectable minimum speed and full speed. It uses a triac for power line switching to reduce motor speed. An external transformer (24 VAC) must be supplied to power the control.

The motor used with the 770-PSC Control must accept a phase proportioning input and be able to operate at minimum rpm for extended periods of time without overheating.
  • Remote and local control of the speed of single phase PSC or shaded pole motors of up to 10 amps; 115, 208/230, or 277 VAC.
Stacks Image 2151
  • Control the speed of a PSC or shaded pole motor locally or remotely
  • Modbus RTU communication with building automation systems
  • Closed-loop control mode will maintain motor speed independent of loading
  • Remote sensing of motor rpm using included easy to attach sensor
  • Motor voltages of 115 to 277 VAC
  • Motor currents up to 10A
  • Open-loop control mode will set the percent of maximum control signal (speed index)
  • Large 32 character LCD screen for readout of values and setting parameters using a menu system
  • LCD display of motor rpm
  • All parameters can be set or read remotely and all input and output values can be read remotely
  • Modbus baud rate, slave ID, and parity can be set using the menu system
Data Sheets