Yaskawa Sigma Servo Drives and Motors, New Zealand

Yaskawa / Sigma servo

A servo amplifier and its motor are a matched pair, and the match is the encoder generation. A Sigma-V amplifier will not run a Sigma-II motor, however close the power ratings look. Send both part numbers or we cannot quote either.

Sigma is the Yaskawa servo range and it is on an enormous amount of imported machinery in New Zealand. Packaging, converting, labelling, filling, robotics and anything with coordinated axes.

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The generations

Establish this first, because it decides what will work with what.

Generation	Amplifier prefix	Motor prefixes
Sigma-II	SGDM, SGDH	SGMAH, SGMPH, SGMGH, SGMSH
Sigma-III	SGDS	SGMAS, SGMPS, SGMGS, SGMSS
Sigma-V	SGDV	SGMJV, SGMAV, SGMGV, SGMSV, SGMPS
Sigma-7	SGD7S, SGD7W	SGM7J, SGM7A, SGM7P, SGM7G

SGD is always the amplifier and SGM is always the motor. The letters after that place it in a generation, and the generations broadly do not mix.

SGD7S is a single axis amplifier and SGD7W is a two axis amplifier. One physical unit running two motors. Worth knowing, because a failed SGD7W takes two axes down and a single axis unit is not a replacement.

Why the pair has to match

The most important thing on this page.

A servo motor carries an encoder, and the amplifier has to speak that encoder's protocol. Yaskawa changed the encoder across generations, so the amplifier and motor are matched by more than voltage and power.

What has to agree	Why
Encoder generation	The amplifier cannot read an encoder it does not know
Voltage class	200 V and 400 V motors and amplifiers are separate
Power rating	An oversized amplifier will not tune properly to a small motor
Cables	Power and encoder cables are generation and connector specific

So a Sigma-V amplifier of the right kW will not run a Sigma-II motor. It is not a tuning problem, it is a protocol mismatch, and there is no adapter.

Two consequences that matter commercially:

Replacing a failed amplifier on an old machine means finding that generation, not a newer equivalent, unless you are replacing the motor and cables too.

And replacing a failed motor means the same in reverse. A newer motor will not talk to the existing amplifier.

Send both part numbers. Off the amplifier and off the motor. We cannot size a servo from one of them.

Reading a motor part number

The motor code carries far more than power, and every field in it can make two motors non-interchangeable.

Field	What it sets
Series	SGMJV, SGMAV, SGMGV and so on. Frame family and inertia class
Capacity code	Rated output. Two characters
Voltage code	200 V or 400 V class
Encoder code	Incremental or absolute, and the resolution
Shaft code	Straight, keyed, tapped, with or without a key
Brake code	With or without a holding brake
Option code	Oil seal, gearbox, connector orientation

The capacity code is not the kilowatts written plainly. Small motors use a letter and digit, and larger ones use two digits representing hundreds of watts. So it reads once you know the scheme and it does not read on sight.

Send the whole string. Guessing at the middle of a Sigma motor number is how a motor arrives that will not fit the machine.

Three fields that catch people

The brake. A motor with a holding brake and one without are different part numbers and different physical lengths. On a vertical axis the brake is what stops the load falling when power is removed, so it is a safety-relevant item and not an upgrade.

The shaft. Straight against keyed decides whether the existing coupling or pulley fits. A keyed shaft in place of a straight one, or the reverse, means new mechanical parts.

The encoder. Incremental against absolute changes how the machine homes, and that is the next section.

Absolute against incremental, and the battery

The most common Sigma service call, and it is usually not a failure.

	Incremental encoder	Absolute encoder
Knows position at power up	No. The axis must home	Yes
Needs a battery	No	Yes, to retain multi-turn count
Battery location		In the amplifier or in the encoder cable

What a flat battery looks like

Symptom	Meaning
Encoder backup alarm at power up	Battery flat or disconnected. Multi-turn data lost
Machine demands homing every start	Position reference gone
Axis at the wrong position after a power cut	Same

That is a consumable, not a failure. A battery and a re-home resolves it, and neither the amplifier nor the motor is faulty.

Two things make it worse than it should be. Clearing the alarm requires a specific reset procedure, and on a machine with mechanical absolute references the axis has to be re-established against them.

So change the batteries on a schedule rather than waiting. They are cheap, the machines are not, and a flat battery on a multi-axis machine means re-homing all of it.

Same pattern as the encoder battery on our Mitsubishi MELSERVO page.

Cables are parts, not accessories

Worth its own section because servo cables fail and get forgotten on orders.

Cable	Notes
Motor power cable	Connector type and length are part of the order code
Encoder cable	Generation specific. Also carries the battery on some arrangements
Brake cable or brake wires	Separate on some motors
Flexing grade	For cable tracks and moving axes

An encoder cable in a cable track is a wear item. Intermittent encoder alarms on one axis of a machine, and only when it moves, is a cable rather than an amplifier.

And standard cable in a flexing application will fail. If a cable has been replaced with ordinary cable it will keep failing, and that is worth checking before replacing electronics.

Tell us the run length and whether the cable flexes.

MECHATROLINK, and the two versions

Yaskawa's motion network, and the point most likely to catch a substitution.

	MECHATROLINK-II	MECHATROLINK-III
Physical layer	Different	Ethernet based
Interchangeable	No
Amplifier interface	Built in or by option, by model	Built in or by option, by model

An amplifier for one will not join a network of the other. So on a networked machine the interface is part of the specification, not a detail.

And an analogue or pulse train amplifier is a different variant again from a networked one. The same generation and power rating comes in several command interfaces, and they are not alternatives.

Tell us how the amplifier is commanded. Network, analogue speed or torque reference, or pulse train.

Where the tuning lives

Item	On a replacement amplifier
Parameters and tuning	Factory defaults
Motor identification	Read from the encoder on most generations
Absolute position	Lost. Re-home the axis
Network address	Set on the amplifier

So a replacement amplifier needs the parameter set, and on a coordinated machine it needs the tuning that matches the mechanics. A default amplifier on a high inertia axis will run and will not run well.

Back the parameters up with the Yaskawa engineering tool while the machine works. On a multi-axis machine that is the difference between a swap and a retune, and retuning a converting or filling machine is not a small job.

Note the network or node address before the old amplifier comes off. A correct amplifier at the wrong address is invisible to the controller.

Before ordering a replacement

Symptom	Check first
Encoder backup alarm, axis wants homing	The absolute encoder battery. A consumable
Intermittent encoder alarm on a moving axis	The encoder cable in the track
Axis drops when power is removed	The holding brake, and whether the motor has one
New amplifier will not run the motor	Generation match. Encoder protocol, not power
Amplifier invisible to the controller	Node address, and MECHATROLINK version
Axis runs but hunts or overshoots	Tuning, not hardware
Overload on one axis only	Mechanics. Bearings, belt tension or a jam
Motor will not couple to the machine	Shaft code. Straight against keyed

What to send us

Both part numbers. The full SGD amplifier code and the full SGM motor code.

A photo of both nameplates if the labels are marginal.

How the amplifier is commanded. MECHATROLINK-II, MECHATROLINK-III, analogue or pulse train.

Whether the encoder is absolute or incremental.

Whether the motor has a brake, and whether the axis is vertical.

Whether you need cables, their length, and whether they flex.

Whether you have a parameter backup.

What we can supply

Amplifiers. SGDM, SGDH, SGDS, SGDV, SGD7S and SGD7W across the voltage classes and power ratings.

Motors. The SGMAH, SGMPH, SGMGH, SGMSH, SGMAS, SGMGS, SGMJV, SGMAV, SGMGV, SGMSV and SGM7 families, with and without brakes.

Matched sets. Where a machine needs amplifier, motor and cables together, we quote them as a set so the generations agree.

Cables and batteries. Power, encoder and brake cables in standard and flexing grades, plus encoder backup batteries.

Option cards. Network and interface options for the amplifiers.

The older generations are discontinued, so much of this is surplus and tested used. That is frequently the only way to keep a machine on its existing amplifier and motor pairing.

A sensible Sigma spares holding

Item	Why
Encoder backup batteries	The most common call-out and the cheapest part
A parameter backup of every axis	Free, and it avoids a retune
One encoder cable per flexing axis	A wear item that stops the machine
A matched amplifier and motor for the most critical axis	Generation supply thins out and does not improve

The batteries and the parameter backups are the two to do this month. Between them they cover the majority of Sigma downtime and neither costs anything meaningful.

We buy Sigma servo

Sigma holds real value, and a matched amplifier, motor and cable set is worth considerably more than the same parts split up, because the next plant needs the generations to agree.

So if you are stripping a machine, keep each amplifier with its own motor and cables, and label the pairs. Motors with brakes are worth more than motors without, so note which is which. See Sell To Us.

Common questions

Can you get a part that is not listed on your site?
Usually. The site shows what we hold, not what we can source.

Can I use a newer amplifier with my existing motor?
Generally no. The encoder protocol changed between generations and there is no adapter.

My machine wants homing every morning.
The absolute encoder battery. That is a consumable, not a failure.

Why do you need the motor number to quote an amplifier?
Because the pair has to match on encoder generation, voltage and power. One number is not enough.

Does the motor come with cables?
No. Power and encoder cables are separate parts, and the grade matters if they flex.

Is a motor with a brake the same part?
No. Different part number and different length. On a vertical axis the brake matters.

Do you supply used equipment?
Yes. On the older generations it is usually the only option, and units are tested before they ship.

What is the lead time?
Ex stock items ship the next working day within New Zealand. We give you a firm lead time with the quote.

Do you quote in NZD?
Yes, in NZD including GST for New Zealand customers.

Send us both part numbers

The amplifier and the motor. On a servo the pair is the product, and we cannot quote half of it. Quotes in NZD including GST.

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Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Yaskawa. Yaskawa, Sigma and MECHATROLINK are trademarks of Yaskawa Electric Corporation. All trademarks, brand names and model numbers are the property of their respective owners and are used here for identification purposes only.