Technical notes · Changzhou Rasta Electromotor Co., Ltd

N-01Migration policy

86 Chinese articles sorted into four buckets

The 86 Chinese articles are what gets sorted. Topics such as EV traction, servo motors, smoke extraction, domestic fans and service networks have no matching product evidence and are not migrated; passages quoting 10–30% or 20–50% savings without a verifiable report are rewritten. Legacy URLs are 301-redirected rather than deleted.

3

Rewritten

Topics with an evidence chain to the product that help selection

12

To merge

The same topic written many times over, to be consolidated

41

Not migrated

EV traction, servo, smoke extraction, domestic fans, service networks — no matching product evidence

30

Not yet sorted

The remainder not yet read through article by article, stated rather than left for the reader to subtract

Legacy URLs are 301-redirected rather than deleted — deletion discards existing indexing and inbound links. "Not migrated" is not a verdict of worthlessness; each can be reassessed once the matching product material exists.

The 7 English articles are handled separately

The 7 English articles are not migrated by translation. One, /was-ist-ein-ec-motor/, has a German slug and reads as a German-to-English translation of unknown origin, with a likely copyright problem — English articles are all rewritten from scratch after a duplication check, with their old URLs 301-redirected.

2026-09-19B

TEAO or TEFC: where the cooling air comes from

The EC100 comes in two versions differing in one respect: what cools the motor. The answer decides overall length, weight, and whether the machine can run slowly for long periods.

TEAO stands for Totally Enclosed Air-Over: no fan of its own, cooled by the airflow of the driven equipment. TEFC stands for Totally Enclosed Fan-Cooled: it carries its own fan and shroud.

For a direct-driven axial fan the TEAO is the natural choice — the fan already moves air, and a second self-cooling fan is redundant weight and length. But the choice carries a condition: the fan must not sit at very low speed for long. Cooling airflow falls with speed while motor losses do not fall in the same proportion.

So power and the enclosure label are not enough: confirm minimum continuous speed, load-side airflow, whether the TEFC fan is shaft-mounted or independently driven, and the associated thermal data. The available material does not establish either version’s continuous low-speed capability.

One caution: on the legacy site the two EC100 detail tables largely duplicate each other, weights included. Whether the two structures really weigh the same is being checked with the factory; until that is confirmed, do not base mounting design on the tabulated figure.

2026-09-19B

Why negative-pressure duty is hard: two curves moving apart

The poultry-house negative-pressure fan was chosen as the ultimate proving duty — not because the airflow is large, but because as pressure rises, power and cooling move in opposite directions.

In this 58-inch sample table, airflow falls and the tabulated power rises as static pressure increases, while the airflow-to-power ratio also falls. That describes this sample at these test points and does not establish the peak-efficiency point of every axial fan.

For the motor two things happen at once: it must deliver more power while the airflow available to cool it is shrinking. If the motor is a TEAO relying on fan airflow, the divergence of those two curves is a real temperature rise.

That is why durability validation happens in a sealed chamber and not by running the machine free in the workshop. The chamber holds negative pressure at a set value so the motor runs continuously in the least favourable combination, exposing the limits of the insulation system and the structure.

A question worth asking during selection: at what static pressure were the stated figures measured. The motor load on the same fan at 0 Pa and at 100 Pa are not remotely the same thing.

2026-09-19C

Air gap, vibration and bearing life are one subject

A uniform air gap is usually discussed as an efficiency topic. On continuously running ventilation equipment it is more of a service-life topic.

An uneven air gap produces unbalanced magnetic pull: the rotor is drawn continuously toward the side where the gap is smaller. The force does not disappear with load — it exists whenever the machine is energised, and it lands on the bearings.

Residual rotor unbalance does something different: it produces a rotating exciting force growing with the square of speed. The two act on the same bearings, one steady, one cyclic.

So the balance grade and air-gap uniformity are not two independent process metrics; they point at the same outcome. It is also why machining follows potting — any distortion introduced during potting is corrected by the later machining operation, rather than hoping the potting itself is precise enough.

A buyer can usefully ask: to which standard is the rotor balanced, to what grade, and how is air-gap uniformity controlled and recorded. Those two questions reveal more about a motor maker than the efficiency figure does.