Emerson Unidrive SP Error Code PS

Emerson PLC & VFD Major System

Model: Unidrive SP | Code: PS

Applicable Systems
Unidrive SP Commander SK EV2000 Mentor MP

Symptoms

The drive trips and displays PS (Internal Power Supply Fault). The internal 10V or 24V power supply circuit is abnormal. This can affect the drive's control electronics, analog I/O, or safety circuit power.

Possible Causes

  • Internal 10V reference supply for analog inputs is overloaded or shorted
  • Internal 24V supply for digital I/O is overloaded or shorted
  • Power supply board component failure (regulator, capacitor, resistor)
  • External device drawing excessive current from the drive's internal supply

Troubleshooting Steps

  1. Step 1: Measure the internal 10V supply at the analog input terminals
    Voltage should read 10V +/-0.5V; if low or zero, the supply is overloaded or faulty
  2. Step 2: Disconnect all external devices connected to the drive's 10V and 24V outputs
    If PS clears, an external device was overloading the supply; identify and fix the faulty device
  3. Step 3: Check the 24V supply at the digital output terminals
    Voltage should read 24V +/-1V; if low, disconnect loads one by one to find the culprit
  4. Step 4: If PS persists with all external devices disconnected, the internal power supply board is faulty
    The power board or driver board needs repair; check for damaged components (burnt resistors, bulging capacitors)

How to Reset

To reset: 1) Disconnect the external load causing the overload. 2) Press RESET. 3) If PS persists, the drive needs repair. Caution: Do not draw more current from the internal supplies than specified in the manual, as this can damage the power supply board.

Frequently Asked Questions

  • Q: What is the 10V reference supply used for?

    The 10V reference is used to power analog input devices like potentiometers (speed reference) and to provide a reference voltage for analog inputs. If this supply is overloaded (e.g., by a shorted potentiometer wire), the analog inputs will not function correctly.

  • Q: How much current can I draw from the internal 24V supply?

    The Unidrive SP's internal 24V supply typically provides up to 200mA. Exceeding this will trip PS. For larger loads, use an external 24V power supply. Check the manual for the exact specification for your drive model.

Related Emerson Fault Codes

Source: Emerson Control Techniques Unidrive SP Advanced User Guide, 2023

Category: PLC & VFD