Description

GATS-A03B Automatic Transfer Switch with Priority Phase, Signal Output and Adjustable V/A Protection

The GATS-A03B is a microcontroller-based automatic transfer switch that takes three lines plus neutral on the input side (N, L1, L2, L3 — AC 3×220V, 50/60Hz) and supplies a single-phase load through a 2P output (Lout + N). It comes in 63A, 80A and 100A and brings together priority phase selection, over-voltage and under-voltage protection, over-current protection with adjustable action time, automatic reconnection, and a separate signal switch output that reports the operating state to an external device. Five display windows read the three incoming line voltages (L1-in, L2-in, L3-in) plus the output voltage (L-out) and the output current (I-out), while L1/L2/L3 and Fault LEDs show which line is feeding the load and why the last operation took place. All values are entered from four front keys: over-voltage 230–300V (default 270V), under-voltage 140–220V (default 170V), over-current 1A up to the rated current, and delays from 1s to 600s. The unit mounts on a 35mm DIN rail.

Size Dimension

Working Principle

The three input lines act as candidate sources rather than three phases carried at once. The microcontroller measures L1, L2 and L3 against the stored voltage window and connects one of them to the output, which is why the 63A / 80A / 100A rating belongs to the single-phase path. Normally the load runs on the line set as priority phase (L1 by default, or Auto). If that line goes above the over-voltage setting or below the under-voltage setting, the switch releases it and moves the load to a reserve phase in less than 0.2s, so the load stays energised as long as one line remains inside the window. Trip timing is graded by the measured voltage: below 350V the unit acts within 0.1s, and above 350V within 0.02s — the faster path matters when a broken neutral pushes line voltage onto the load. A 5V hysteresis band stops the switch chattering when the voltage sits right at a threshold. When the priority phase returns and holds through the return delay (1–600s), the unit transfers back on its own, and the signal output follows the change so the event can be logged remotely.

Key Features

Signal switch output — a dedicated terminal pair on the output side, shown in the wiring diagram as a contact separate from the power circuit, for remote indication or monitoring.
Five display windows — three incoming line voltages plus output voltage and output current, so supply quality and load can be checked without a clamp meter.
Priority phase selection — L1, L2, L3 or Auto, chosen in the setup menu.
Graded trip speed — 0.1s under normal conditions, 0.02s once voltage exceeds 350V.
Microcontroller measurement — voltage accuracy better than 1%, maximum operating phase voltage 350V.
Adjustable timing — power-on delay 1–600s (default 5s), protection recovery delay 1–600s (default 30s).
Over-current control — value 1A to the rated current, action time 0.1–10s, plus a continuous over-current retry count of 0–20 (OFF by default).
Setting from four keys — M for menu and reset, ▲/▼ for digits, and a manual ON/OFF key for isolating the load.
Service life — electrical 10⁵ operations, mechanical 10⁶ operations.

Protection Settings and Defaults

Every threshold is adjustable, and units leave the factory on the values below unless a different pre-set is agreed with the order:

Over-voltage (oU) — range 230–300V, default 270V.
Under-voltage (uU) — range 140–220V, default 170V.
Over-current (oC) — range 1A up to 63A, 80A or 100A according to the model; action time (Ctt) 0.1–10s, default 0.5s.
Continuous over-current count (CC) — 0–20, OFF by default; useful for telling a real wiring fault apart from a single starting surge.
Trip delay — 0.1s below 350V, 0.02s above 350V, applied to both the over-voltage and the under-voltage function.
Setting rule — the under-voltage value stays below the nominal voltage and the over-voltage value above it. On the AC 110V version keep under-voltage near 90V and over-voltage near 140V; an under-voltage figure set close to 220V would read a healthy 110V supply as too low and the load would stay off.

Installation

Mount on a 35mm DIN rail inside a distribution board; keep to an altitude of 2000m and an ambient range of -25°C to +50°C.
Wire N, L1, L2 and L3 to the four input terminals on the upper side; take N and Lout from the lower side to the load, following the front-panel markings.
Connect the two signal switch terminals to the monitoring input, and confirm the contact form and rating before wiring them into a PLC, RTU or alarm panel.
Isolate the supply before wiring and tighten the terminal screws firmly, particularly on the 80A and 100A versions.
Power up, check that the three input windows read plausible values, then step through the setup menu to confirm oU, uU, oC, Ctt, CC, LS, Pt and rt.
Record the final settings in the board documentation; the manual ON/OFF key isolates the load during maintenance.

Applications

Apartment blocks and multi-unit residential boards fed from a three-phase riser, shops and small offices, telecom and monitoring cabinets, pumping and irrigation control, lighting circuits, and unattended single-phase installations where the transfer or fault event needs to be reported back to a control room rather than read on the front panel.

Technical Parameters

Technical Data

Item	Data
Supply terminals	N, L1, L2, L3
Rated supply voltage	AC 3×220V (N-L1/L2/L3)
Output	Single-phase, 2P (Lout + N), plus signal switch terminals
Rated frequency	50/60 Hz
Umax setting range	230–300V
Umin setting range	140–220V
Auto-reclosing delay (Ton)	1–600s
Return delay to priority phase	1–600s
Switch delay to reserve phases	<0.2s
Voltage hysteresis	5V
Over-voltage trip delay	0.1s when the measured voltage is below 350V; 0.02s when it exceeds 350V
Under-voltage trip delay
Voltage accuracy	<1%
Max. operating phase voltage	350V
Rated operating current	63A / 80A / 100A
Max. operating current	63A / 80A / 100A
Display	5 windows: L1-in, L2-in, L3-in voltage; L-out voltage; I-out current
Indication	L1 / L2 / L3 output LEDs and Fault LED
Keys	M (menu selection / reset), ▲ (digit +), ▼ (digit −), manual ON/OFF
Pollution degree	3
Electrical life	10⁵ operations
Mechanical life	10⁶ operations
Altitude	≤2000m
Ambient temperature	-25°C to +50°C
Permissible relative humidity	≤50% at 40°C, without condensation
Storage temperature	-25°C to +55°C
Mounting	35mm DIN rail
Dimensions (W×H×D)	90 × 95 × 66 mm per dimensional drawing; 63A body 96mm and 80A/100A body 104mm per the specification sheet

Setup Menu, Setting Ranges and Factory Defaults

Code	Function	Setting Range	Factory Default
Pt	Power-on delay time	1–600s	5s
rt	Protection recovery delay	1–600s	30s
oU	Over-voltage protection value	230–300V	270V
uU	Under-voltage protection value	140–220V	170V
LS	Priority phase	L1 / L2 / L3 / Ato (auto)	L1
oC	Over-current protection value	1A–63A / 80A / 100A according to model	Rated current of the model
Ctt	Over-current protection action time	0.1–10s	0.5s
CC	Continuous over-current protection frequency	0–20	OFF

Model Range and Voltage Versions

Model	Material Code	Rated Current	Over-Voltage Range (220V / 110V)	Under-Voltage Range (220V / 110V)	Defaults (220V / 110V)	Packing
GATS-A03B 2P 63A AC220V	004040000226	63A	230–300V / 110–300V	140–220V / 80–220V	OV 270V / 140V UV 170V / 90V	30 pcs
GATS-A03B 2P 80A AC220V	004040000227	80A				30 pcs
GATS-A03B 2P 100A AC220V	004040000228	100A				30 pcs

The ranges above are the spans the electronics accept and are shared by the 220V and 110V versions; on a 110V network the settings must be kept around the 110V nominal level.

Comparison with GATS-A02

Item	GATS-A02	GATS-A03B
Display windows	4 (L1, L2, L3 voltage + output current)	5 (L1, L2, L3 voltage + output voltage + output current)
Signal switch output	—	Included
Input / output arrangement	N, L1, L2, L3 in; Lout + N out; AC 3×220V, 50/60Hz
Protection and setup menu	Identical: Pt, rt, oU, uU, LS, oC, Ctt, CC
Current ratings	63A / 80A / 100A

FAQs

1. What is the GATS-A03B automatic transfer switch?

It is a microcontroller-based, DIN-rail automatic transfer switch with priority phase and signal output. Three lines and a neutral come in (N, L1, L2, L3 — AC 3×220V, 50/60Hz), and the load is fed through a 2P output (Lout + N) from whichever line sits inside the set voltage window. Ratings are 63A, 80A and 100A, and five display windows show the three input voltages plus the output voltage and output current.

2. What are its core functions?

Priority phase — L1, L2, L3 or Auto; return to priority delayed 1–600s.
Automatic transfer — changeover to a reserve phase in <0.2s, without operator action.
Signal switch output — a separate terminal pair reports the operating state to an external device.
Voltage protection — over-voltage and under-voltage, trip in 0.1s below 350V and 0.02s above 350V.
Over-current protection — value 1A to the rated current, action time 0.1–10s, retry count 0–20.
Auto reconnect — protection recovery delay 1–600s, default 30s, so no manual reset is needed.
Metering and indication — five readings on the display plus L1 / L2 / L3 / Fault LEDs.

3. Which parameters decide the correct selection?

Load current — choose 63A, 80A or 100A above the calculated single-phase load current.
Supply arrangement — three lines plus neutral must be available; rated supply is AC 3×220V (N-L1/L2/L3).
Voltage version — AC 220V or AC 110V, each with its own default trip values.
Remote signalling — pick the A03B where a status output is needed; the A02 suits panels read on site.
Setting window — over-voltage 230–300V, under-voltage 140–220V on the 220V version.
Board space and environment — 35mm DIN rail, roughly 90 × 95 × 66mm, ambient -25°C to +50°C.

4. Which models and options are available?

GATS-A03B 2P 63A AC220V — material code 004040000226, 220V or 110V version.
GATS-A03B 2P 80A AC220V — material code 004040000227, 220V or 110V version.
GATS-A03B 2P 100A AC220V — material code 004040000228, 220V or 110V version.
Packing — 30 pcs per carton for each rating.
Pre-setting — custom default trip values can be programmed before shipment on request.

5. What standards does it follow and which markets does it suit?

The switch carries the CE marking and is designed to pollution degree 3, altitude ≤2000m, with an electrical life of 10⁵ and a mechanical life of 10⁶ operations. It suits 3×220V/380V networks feeding single-phase 220V loads, while an AC 110V version covers 110V systems — which together cover Asia, Africa, the Middle East, Latin America and Europe. Ask our sales team for the current certificates and test reports so the documents match your project specification or customs file.

6. What should be noted for installation and maintenance?

Isolate first — switch off the upstream supply before wiring or servicing.
Follow the terminal marks — N, L1, L2, L3 to the input side; N and Lout to the load; signal switch terminals to the monitoring circuit.
Check the signal contact rating — confirm the contact form and permitted load before connecting a PLC, RTU or alarm panel.
Tighten properly — loose terminals cause heating, most noticeably at 80A and 100A.
Confirm the settings — step through oU, uU, oC, Ctt, CC, LS, Pt and rt at commissioning and record the values.
Respect the environment limits — -25°C to +50°C in service, humidity ≤50% at 40°C without condensation.
Routine checks — compare the input readings against the output reading, and review the over-current count; repeated events usually point to the load or the wiring rather than the switch.

Why is it called 2P when there are three line inputs?

Input side — N, L1, L2, L3; the three lines are candidate sources, measured together but never loaded together.
Output side — one selected line plus neutral, i.e. Lout + N = 2P feeding a single-phase load.
Current rating — 63A / 80A / 100A applies to that single-phase output path, not to three separate phases.

What does the “0.1s / 0.02s above 350V” trip delay mean?

It is a delay, not a setting — 350V is not adjustable; it is the level at which the unit switches to fast operation.
Below 350V — the switch acts within 0.1s once a voltage fault is confirmed.
Above 350V — the switch acts within 0.02s, limiting the energy that reaches the load during a severe rise such as a broken neutral.
Applies to both — the same graded timing governs over-voltage and under-voltage, so the two rows in the data table carry identical figures.

The 110V version lists an under-voltage range up to 220V — is that correct?

Yes, with one line of explanation. The 110V and 220V versions run on the same measuring platform, so the menu accepts one wide span for both. It is a setting range, not a recommended value.

On a 110V network — keep the under-voltage setting near the 90V default and the over-voltage setting near 140V.
If set wrongly — an under-voltage value above the nominal voltage makes every reading look too low, and the load stays disconnected.

GATS-A03B 2P ATS with Signal Feedback