BA4401 Variable Frequency Drive AFFINITY 37.0kW 3-ф/380

BA4401 — Control Techniques Affinity rated 37 kW, three-phase 380–480 V supply, 74 A rated current, frame BA4, IP20. A drive for large building/industrial ventilation and pumping systems.

Typical applications:

• Main fan of a large site or smoke extraction
• High-capacity pump station
• Refrigeration compressor, chiller

Note: three-phase 380 V supply. Two PID loops, sleep/wake, unit cascade, fire mode. V/f and RFC sensorless control. Modbus RTU, BACnet, Metasys N2 built in; extended protocols via a Solutions module. On the larger frames the braking module and resistor are usually external — confirm the configuration and a compatible resistor against the part number. Modern in-stock replacement: Veichi AC310.

Control Techniques Affinity — a dedicated HVAC, pump and fan frequency inverter

Affinity (factory name Building Automation HVAC/R drive, Nidec Control Techniques) is not a general-purpose industrial inverter but a drive built specifically for building automation: fans, pumps, compressors, air-handling units, chillers and cooling towers. In our catalogue the line spans 3 to 90 kW, three-phase 380–480 V supply, IP20 housing for cabinet mounting. Part numbers follow the frame sizes: BA1 (3–5.5 kW), BA2 (7.5–15 kW), BA3 (18.5–30 kW), BA4 (37–55 kW), BA5 (75–90 kW). It is an asynchronous-motor drive — not a servo.

How Affinity differs from an ordinary inverter

Per the manual (Affinity Advanced User Guide, Nidec CT) the drive runs in two modes: open-loop V/f (linear, square, dynamic — typical for fans and centrifugal pumps) and RFC, sensorless vector control. There is no closed-loop encoder mode in the standard build, so it is not the right class for precision positioning. For HVAC duty, though, Affinity offers what a plain inverter does not:

• Two independent PID loops (Menu 14) — for example, one holds line pressure while the other holds temperature. This is the series' key feature for an automation engineer.
• Sleep/wake modes — the drive sleeps at low demand and wakes itself, saving pump life and energy.
• Pump/fan cascade control and functions for multi-unit stations.
• Fire mode — forced smoke-extraction operation in an emergency, a typical requirement for smoke-control drives.

Connecting to the building management system

Affinity was designed for buildings: Modbus RTU is built in, and through the Building Automation Network it speaks BACnet and Metasys N2. That is the main reason it ends up in building management systems. Additional protocols (PROFIBUS, CANopen, EtherCAT, Ethernet, LonWorks) are added via plug-in Solutions modules in two expansion slots — they must be ordered separately for the specific network, so confirm the protocol set against the part number.

EMC and braking — what to confirm before ordering

The manufacturer states a built-in mains EMC filter and a built-in brake control function (Menu 12) as part of the standard drive. That is a plus, but confirm the exact configuration — whether the filter and brake chopper are fitted on your specific frame size, and which external braking resistor is needed — against the actual part number. Fans and centrifugal pumps rarely need intensive braking anyway (inertia is dissipated by coasting), whereas drives with fast cyclic stops should budget a braking resistor separately.

When Affinity is a good fit, and when it is not

Affinity today is largely a legacy line, requested mostly as a replacement on building-automation sites where it was fitted from the original project. If the brand is not a requirement and you need a modern in-stock drive for a pump or fan, compare it with our Veichi AC310 and AC10 inverters: built-in PID, sleep mode, shorter delivery for HVAC duty.