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18 D6.3.4/0715-0716/E

4.5 Motor protection

Each compressor has a motor protector. An external overload protection is not necessary.

4.5.1 Over-current thermal protection switch for single-phase motors – System A

WARNING

Compressor under voltage! Electrical shock! When the motor stops due

to the over-current thermal protection switch, the compressor is still under

voltage!

This bimetal switch is installed in the terminal box. It is heated by the motor current and by the

motor bundle of laminations, and combines the function of an over-current tripping device and

thermal protection switch. When the switch responds, it interrupts the voltage supply to the motor

directly, not the control line. When the motor winding cools off, it switches on again

automatically.

4.5.2 Thermistor protection – System W

All 3-phase motors with a “W” in the motor code have a thermistor protection device. The

temperature-dependent resistance of the thermistor (also PTC-resistance) is used to sense the

winding temperature. A chain of three thermistors (on 2 and 3 cylinder compressors) or two

chains of three thermistors each (on 4, 6 and 8 cylinder compressors) connected in series are

embedded in the motor windings in such a manner that the temperature of the thermistors can

follow with little inertia.

An electronic release module is required which switches a control relay, depending on the

thermistor resistance. The release module INT69-2 for one thermistor chain or two chains with a

5-minute time delay, INT69TM-2 for two chains, is installed in the terminal box to which the

thermistors are connected.

Caution: The maximum test voltage for thermistors is 3V.

The total resistance of the thermistor chains on a cold compressor should be ≤ 1800Ω.

Internal wiring: The current compressors use a new generation of thermistor protection

(INT69-2 & INT69TM-2) that has the same main features as the previous one (INT69 &

INT69TM).

INT69-2 (K, L, D2, D3, 2D, 3D) INT69TM-2 (D4, D6, D8, 8D)

Legend

L ...... Voltage connection 3+4 ........ Cable bushings of thermistor connections

N ...... Neutral connection in terminal box (K, L, 2S not marked)

1+2 ... Thermistor chain connection S1-S4 .... Cable bushings of thermistor connections

12 ..... Alarm connection in terminal box (4, 6 & 8 cyl.)

14 ..... Control circuit T1+T2 ... Thermistor chain (about 90Ω to 750Ω per

11 ..... Control voltage connection chain at +20°C)

A1 .... Release module NAT....... Nominal response temperature

Figure 15

Protection class IP20.

Emerson Copeland 2D Series User Manual

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