EnergAir metacentre VSD-R

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Overview

Important Technical Specifications
Usage Features
Maintenance Features

The VSD-R 4-20mA Box is a specialized air compressor supervisory and control unit designed to integrate with Variable Frequency Inverter Drive (VFD) panels that feature a 4-20mA speed control input. It also functions in cooperation with a management system unit. This device allows a fixed-speed, load/unload air compressor to be converted into a variable speed unit with advanced management system supervisory and control functionality, providing total synergy with energy control and VSD compressor-aware functions of the management system unit. Each air compressor requiring VSD-R integration must be equipped with an individual VSD-R Box and VSD panel.

Important Technical Specifications

VSD-R 'mA' Box:

Dimensions: 291mm x 241mm x 152mm
Weight: 6.5kg (14lb)
Mounting: Wall, 4 x screw fixings
Enclosure: IP54, NEMA 12
Supply: 230Vac +/- 10% or 115Vac +/- 10%
Power: 50VA
Temperature: 0°C to 46°C (32°F to 115°F)
Humidity: 95% RH non-condensing

VSD/VFD Unit Basic Requirements:

Speed Reference Input: Must be equipped with a 4-20mA speed reference input.
- 20mA = maximum loaded motor speed.
- 4mA = minimum loaded motor speed.
Remote Start/Stop: Must have an input for remote volt-free switching contact.
- Open Circuit = Stop
- Closed Circuit = Start/Run
Drive Fault Output: Must have a volt-free switching contact output that is normally closed and opens in the event of a drive fault. The contact should close within 2 seconds at power-up and remain closed when the drive is stopped, unless a fault occurs.

Compressor Basic Requirements:

Load/Unload Regulation: Must be equipped with a load/unload regulation system, or a facility for remote load/unload control with a volt-free switching contact input.
Pressure Control Range: Accommodates 1bar to 600bar with an appropriate sensor.
Main Drive Motor: Must be suitable for variable speed 'inverter drive' operation (generally induction motors from 1990 onwards, restricted to 50% turndown capability).
Motor Contactor: Must be fitted with a contactor or start/delta contactor set capable of isolating the motor from the power supply in emergency stop situations.
Controller/Controlling System: Must have full main motor and regulation control functionality, as well as all required air compressor unit safety functions and features installed and operational.

Usage Features

General Operation: The VSD-R Box controls the speed of an air compressor's main motor in response to pressure variations (demand). It can function as a standalone VSD air compressor unit or in conjunction with a management system. The VSD-R Box performs all pressure regulation functions and controls the compressor using load/unload commands, integrating with the compressor's pressure switch or remote load/unload input.

The main drive motor operates only when the compressor's controller requests it to run, ensuring all compressor controller proprietary and safety features remain intact. The VSD-R Box controls the compressor's main motor contactor(s), operating them in response to a run request from the compressor's controller. Power is applied to the VSD panel (5) and then to the main motor (6) only after the contactor(s) have energized correctly (4). The contactor(s) are used for safety isolation, energizing prior to power application and de-energizing after power removal, prolonging contactor service life.

Any star/delta timing or motor run-on time implemented in the compressor controller can remain. The VSD-R Box monitors the compressor's response to load requests, generating a fault if an incorrect response is detected. When loaded, the VSD-R Box varies the motor speed based on pressure demand. When unloaded but still running (run-on time), the motor runs at a predefined 'off load' speed. The main motor stops in a controlled manner when the compressor controller no longer requests it to run. In an emergency stop or trip, the VSD-R Box immediately removes power from the main motor and de-energizes the contactor(s).

User Interface and Display: The VSD-R features an LCD display showing the detected 'Delivery' pressure (primary display) and selected user menu items. Status symbols indicate system management unit activity, compressor running/loading status, service maintenance, and fault conditions. Indicators include a green LED for run status (off for not running, flashing for offload, on for loaded) and a red LED for fault status (off for no fault, flashing for fault).

Menu Navigation: The menu system allows access to various settings and information. Users can navigate through pages (P00, P01, P02, etc.) and items using UP/DOWN buttons. An access code is required for protected settings. The display can be locked on a selected menu item.

User Display Menu Items:

C> (VSD-R Box status): Shows network address and status block number.
SP (Percent motor speed (%)): Indicates detected motor speed relative to maximum.
Tm (Motor temperature): Displays motor temperature.
T2 (2nd temperature (optional)): Displays an optional second temperature.

Operating Pressure Set Points (P01):

Pu (Unload pressure set point): Sets the unload pressure.
PL (Load pressure set point): Sets the load (VSD target) pressure.
P> (Pressure Units): Selects display units (bar, psi, or kPa).
T> (Temperature Units): Selects display units (°C or °F).

Error Log (P02): Stores the last 15 faults in chronological order, with '01' being the most recent.

Maintenance Features

Fault Codes: The VSD-R Box provides fault codes for various shutdown and alarm conditions:

0010E Emergency Stop (option): Indicates an emergency stop.
0040E Frequency Inverter Drive, VSD, Fault: Requires examination of the drive unit display and manual.
0080E Contactor feedback fault (CF): Indicates a contactor feedback issue.
0115E 4-20mA Delivery P. Sensor Fault: Sensor fault.
0125E Motor temperature sensor fault: Motor temperature sensor fault.
0135E 2nd Temperature sensor fault: Second temperature sensor fault.
0821E Short circuit condition detected: Check all VSD-R inputs and outputs.
0836E PLL unlocked error: PLL unlocked error.
2050A Auxiliary Alarm input: Auxiliary alarm.

Fault Reset: A fault code display can be reset by pressing the VSD-R Box RESET button once the fault condition is resolved.

Compressor Not Responding: If the compressor does not respond to a 'Remote Load' signal within 60 seconds, the VSD-R Box assumes the compressor is 'not available'. The 'remote load' signal is pulsed every 10 seconds until a response is detected, and the condition automatically resets. Users should check if the compressor has been started.

Compressor Faults: The VSD-R Box does not detect individual compressor faults; these should be viewed on the compressor controller. The VSD-R Box will detect any compressor shutdown or run inhibit as a 'not ready' signal, displaying a continuous 'Alarm' symbol and inhibiting VSD motor operation. The management system (if connected) will show the compressor as 'not available'.

Power Disruption Recovery: The VSD-R Box is always active and will automatically recover and become active when power is re-established after a disruption. It is recommended that the compressor controller has a 'power failure automatic restart' facility.

Pressure Regulation Control: If communications with the management system are disrupted, pressure regulation control defaults to 'local' (according to VSD-R Box upper and lower pressure settings). It automatically re-activates 'Remote regulation control' when communications are re-established.