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Motor Enclosure Selector

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About This MicroSim

A motor enclosure decides how the motor gets rid of its heat and how well its windings are protected from the air around it. FanPedia (page 73) lists five enclosures used by Twin City Fan: open drip proof (ODP), totally enclosed fan cooled (TEFC), totally enclosed air over (TEAO), totally enclosed non-ventilated (TENV) and explosion proof (EXPL).

This MicroSim shows ten illustrative fan jobs in a fixed order. For each job you recommend one enclosure. Your first choice on each job is the scored one:

  • a choice in the job's accepted set reads "✓ Correct:" followed by the reason;
  • any other choice reads "✗ Not this one. Reread the job and the card for the enclosure you chose, then try again." and that enclosure is crossed out;
  • you keep choosing until you reach an accepted enclosure; later tries never change the score. The reason and the accepted answer appear only once you reach a correct choice.

Job 1 accepts two answers: ODP is acceptable in a clean, dry room, and TEFC also works. Picking TEFC there adds "ODP would also have been acceptable here."

Five reference cards, one per enclosure, can be opened at any time. Each shows a side-view sketch of the motor with its cooling path (room air through the windings, an external fan blowing over the frame, the fan's own airstream, or heat leaving through the frame) and the IP ratings and duties FanPedia maps to it. Reading a card is exploration and is never scored.

The running count reads "First-try correct: n of 10". After job 10 a summary lists each job, your first choice and the accepted answer, and states whether mastery (8 of 10 on the first try) was reached.

# Job (short) Accepted
1 Clean, dry indoor supply fan ODP, TEFC
2 Rooftop exhaust, rain and dust TEFC
3 Vaneaxial, motor in the housing airstream TEAO
4 Belt drive, motor in the air stream TEAO
5 Textile plant, lint, larger frame accepted TENV
6 Solvent paint spray room, classified for gases EXPL
7 Grain handling, classified for combustible dust EXPL
8 Paper mill, IEEE 841 specified TEFC
9 IP55, general purpose, non-hazardous TEFC
10 IP22, clean indoor ODP

How to Use

  1. Read the job. Open any reference card with the Card list (or press C to step through them).
  2. Press an enclosure button under Recommend (or keys 1–5). Read the feedback.
  3. If the choice was wrong, choose again; crossed-out enclosures are already ruled out.
  4. Once you reach an accepted enclosure, press Next job (or Enter). After job 10, read the summary and press Start over to try again.

Keyboard: 1 ODP, 2 TEFC, 3 TEAO, 4 TENV, 5 EXPL; C steps through the reference cards; Enter goes to the next job once the job is solved. Tab reaches every button and the card list; Enter or Space presses a focused button.

Data label: "Illustrative jobs · Source: FanPedia p. 73", shown at the bottom left of the drawing.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

<iframe src="https://moroshek.github.io/FanTASTIC-textbook/sims/ch14-motor-enclosure-selector/main.html"
        height="547px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Learning Objective

The learner will recommend a motor enclosure (ODP, TEFC, TEAO, TENV or EXPL) for each of ten described fan jobs, with at least 8 of 10 first-attempt choices falling in the accepted set (Bloom: Evaluate, verb: recommend).

Audience

Adult professional development: new application engineers, sales staff, representatives and facilities staff.

Duration

10–15 minutes

Prerequisites

  • Motor enclosure; ODP, TEFC, TEAO, TENV and explosion proof motors
  • Intended duty (GD, SD, IEEE 841, IEEE 45, DFG) and IP ratings
  • Hazardous locations, from Chapter 14

Activities

  1. Recommend (8 min): For each job, ask the chapter's two questions first: is the area classified as hazardous, and what is in the air around the motor? Then commit a choice.
  2. Compare (3 min): Open the cards for TEFC and EXPL side by side in turn. Both have an external fan; what makes EXPL different, and why is it not the answer for job 9?
  3. Review (4 min): Use the summary to find the jobs you missed and say which fact on the card would have decided each.

Common Misconceptions Addressed

  • ODP is fine anywhere indoors, even in dirty or wet air: jobs 1, 2 and 10 separate clean, dry air from wet and dirty air.
  • An explosion-proof motor is needed whenever the air is dirty: job 2 is dirty but not classified, so it is TEFC.
  • A TEAO motor cools itself the way a TEFC motor does: the TEAO card shows no fan of its own, only the fan's airstream (jobs 3 and 4).
  • IP55 always means explosion proof: job 9 maps IP55 to TEFC in a non-hazardous area.
  • TENV is simply a better TEFC with no downside: job 5 states the cost, a hotter motor in a larger frame.

Assessment

  • First-try score shown as "First-try correct: n of 10"; mastery is 8 of 10 on the first attempt.
  • Follow-up: a European specification asks for ATEX motors. What does the chapter say about substituting a standard EXPL motor?

References

  1. Twin City Fan & Blower. FanPedia: The Fan & Blower Encyclopedia, p. 73 (Motor Specifications: Enclosure and Intended Duty). PDF
  2. Twin City Fan & Blower. FanPedia online - the online edition of the same reference.
  3. NEMA. ANSI/NEMA MG 1, Motors and Generators - enclosure and duty definitions for industrial motors. NEMA
  4. NFPA. NFPA 70, National Electrical Code, Article 500 - classes, divisions and groups for hazardous locations. NFPA