Yaskawa SGD7S Servo: Choosing a Compatible Amplifier

The Sigma-7 series — amplifier SGD7S, motor SGM7 — is the servo platform behind a large share of Asian machine tools, electronics assembly, packaging and robot cells. It is a fast, high-resolution platform, and that is exactly why a failure is painful: the axis stops mid-cycle and the machine cannot simply be restarted on a generic drive. This guide covers the checks that decide whether a compatible amplifier will drop into your cabinet and run the axis.

First: read the alarm before you order

Sigma-7 amplifiers display an alarm code in the format A.xxx. These are the codes that come up most often in breakdown calls — confirm against the manual for your amplifier version before acting:

Only the alarm codes that return immediately after a reset — typically CPF00/CPF01 and repeated A.020 — reliably mean "buy hardware". Everything else deserves fifteen minutes with a meter and a backup file first.

Read the model number before you order

An "SGD7S" is a family, not a part number. The full reference carries two pieces of information that decide whether a spare will work:

• The capacity code — sets the rated current. Two amplifiers with the same physical frame can carry very different current ratings, so match the code, not the shape.
• The suffix after the capacity — identifies the command interface and options: analog/pulse reference, EtherCAT, or MECHATROLINK, plus brake and safety options. These variants are not interchangeable: the controller speaks one of them.

Copy the whole reference off the amplifier's nameplate and the motor's nameplate. The motor side matters just as much — see check 4 below.

The seven checks before ordering a compatible amplifier

1. Capacity and rated current. Match or exceed the failed unit's rating, and confirm whether the application runs the amplifier in continuous or peak-heavy duty.
2. Supply class. 200 V and 400 V series are not interchangeable. Read the nameplate, not the cabinet door sticker.
3. Command interface. Analog/pulse, EtherCAT or MECHATROLINK — this is the single most common reason a "compatible" amplifier sits dead on the bench with the right power and the wrong network.
4. Motor pairing. Record the motor model (for example SGM7J, SGM7A or SGM7G) and its encoder type. Drive and motor are specified as a pair, and the encoder resolution has to match what the amplifier expects.
5. Absolute encoder and battery. Sigma-7 motors use a high-resolution absolute encoder. If the battery is flat or was disconnected, you will re-home the axis after the swap — plan for it.
6. Brake and safety options. A holding-brake motor needs the brake output wired and the parameter set correctly; the STO safety function has to be wired the way your machine expects.
7. Frame, mounting and regeneration. Compare depth against the cabinet, terminal layout against the existing cables, and reuse the regenerative resistor only if it measures within specification.

The absolute encoder is the part buyers forget

On an absolute system the amplifier and motor share a position reference held by a battery in the encoder cable or the amplifier. Two practical rules:

• Change the battery before you change the amplifier if it is due — a flat battery during a swap turns a 30-minute job into a re-homing and re-referencing exercise.
• Back up the parameter set first. If the old amplifier still powers up, that file is worth more than the hardware. SigmaWin+ and the controller's own backup function both work; use whichever your integrator standardised on.

Where compatible units fit

A generic compatible servo kit is built to the mounting pattern, terminal layout, encoder interface and key ratings of the series it replaces, so it mounts in the same place and accepts the same motor and encoder cables. For MRO buyers the practical gain is lead time and cost on a platform the original manufacturer has moved past — and a spare you can standardise across several machines.

Our standing recommendation for a first order: buy one, bench-test it on the actual axis, then buy the batch. Send us photos of the amplifier and motor nameplates plus your controller model, and we will confirm capacity, interface and encoder type before you pay.

Installation checklist

• Photograph and label every connector: motor power, encoder, control I/O, network, brake.
• Back up parameters and, on absolute systems, record the multi-turn data before disconnecting.
• Fit a fresh encoder battery and write the date on it.
• Keep the motor phase order U/V/W correct — a swapped pair runs the axis backwards or trips on overload.
• After the swap, run the tuning or auto-tune routine the controller expects, then verify the axis in both directions at low speed before production.
• Re-torque the power terminals after the first heat cycle and confirm the fan runs.

Built for hot and humid panels

Servo electronics fail from humidity and salt air long before they fail from hours. Compatible units carry conformal coating and anti-salt-fog treatment on the boards, for coastal plants and washdown areas. The amplifier is fed from a 200/400 V class supply; the panel's 50 or 60 Hz network does not change the servo specification, and the control electronics are isolated from mains frequency.

Stock, warranty and shipping

Units marked In Stock dispatch within 2–4 business days after payment. Every unit is inspected before shipment and covered by a 12-month warranty against manufacturing defects, with worldwide shipping.

Looking for the part itself? See the Compatible Yaskawa SGD7S / SGM7 Servo Kit — inspected before shipment, tropicalized for humid climates, 12-month warranty.

Related products

Disclaimer: this article refers to brand names and model numbers for compatibility reference only. The parts we supply are generic aftermarket compatible parts, NOT original OEM products. All trademarks are the property of their respective owners. Always confirm the exact model, revision and ratings against your nameplate before ordering.