Norms of acceptance tests. AC motors

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 1 General Rules

Norms of acceptance tests. AC motors

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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1.8.15. AC motors with voltage up to 1 kV are tested according to paragraphs 2, 4b, 5, 6.

AC motors with voltages above 1 kV are tested according to paragraphs 1-6.

1. Determining the possibility of switching on without drying electric motors with voltages above 1 kV.

AC motors are switched on without drying, if the value of insulation resistance and absorption coefficient is not lower than those indicated in Table 1.8.9.

2. Measurement of insulation resistance.

Permissible insulation resistance values for electric motors with voltages above 1 kV must comply with the standards given in Table 1.8.10.

For synchronous electric motors and electric motors with a phase rotor for a voltage of 3 kV and higher or a power of more than 1 MW, the rotor insulation resistance is measured with a megohmmeter for a voltage of 1000 V. The measured resistance value must be at least 0,2 MΩ.

3. Power frequency high voltage test.

Produced on a fully assembled electric motor.

The stator winding is tested for each phase separately relative to the housing with the other two connected to the housing. For motors that do not have outputs for each phase separately, it is allowed to test the entire winding relative to the housing.

The values of test voltages are given in Table 1.8.11. Duration of test voltage application 1 min.

4. DC resistance measurement.

The measurement is made with the machine almost cold.

a) Stator and rotor windings*

The measurement is made for electric motors with a voltage of 3 kV and above. Reduced to the same temperature, the measured resistance values of the various phases of the windings, as well as the excitation windings of synchronous motors, should not differ from each other and from the initial data by more than 2%.

b) Rheostats and ballast resistors

For rheostats and starting resistors installed on electric motors with a voltage of 3 kV and above, the resistance is measured on all branches. For electric motors with voltages below 3 kV, the total resistance of the rheostats and starting resistors is measured and the integrity of the taps is checked.

The resistance values should not differ from the original values by more than 10%.

5. Checking the operation of the electric motor at idle or with an unloaded mechanism.

The duration of the check is at least 1 hour.

6. Checking the operation of the electric motor under load.

It is produced under the load provided by the process equipment at the time of commissioning. In this case, for an electric motor with an adjustable speed, the control limits are determined. The thermal and vibration state of the engine is checked.

* The DC resistance of the rotor winding is measured for synchronous motors and asynchronous motors with a phase rotor.

Table 1.8.9. Permissible values of insulation resistance and absorption coefficient for stator windings of electric motors

Power, rated voltage of the electric motor, type of winding insulation	Criteria for assessing the condition of the stator winding insulation
	Insulation resistance value, MΩ	The value of the absorption coefficient R₆₀/R₁₅
1. Power more than 5 MW, thermosetting and mica compounded insulation	At a temperature of 10-30 ºС, the insulation resistance is not lower than 10 MΩ per 1 kV of the rated line voltage	Not less than 1,3 at a temperature of 10-30 ºС
2. Power 5mW and below, voltage above 1KV, thermoset insulation
3. Motors with mica compound insulation, voltage above 1 kV, power from 1 to 5 MW inclusive, as well as motors of lower power outdoor installation with the same insulation, voltage above 1 kV	Not lower than the values specified in Table 1.8.10.	At least 1,2
4. Motors with mica compound insulation, voltage above 1 kV, power over 1 MW, except for those specified in clause 3	Not lower than the values specified in Table 1.8.10.	-
5. Voltage below 1KV, all kinds of insulation	Not less than 1,0 Mohm at a temperature of 10-30 ºС	-
6. Rotor winding	0,2	-
7. Temperature indicators with connecting wires, bearings	In accordance with the manufacturer's instructions

Table 1.8.10. The lowest allowable values of insulation resistance for electric motors (Table 1.8.9, items 3, 4)

Winding temperature, ºС	Insulation resistance R_60", MOhm, at rated winding voltage, kV
Winding temperature, ºС	3-3,15	6-6,3	10-10,5
10	30	60	100
20	20	40	70
30	15	30	50
40	10	20	35
50	7	15	25
60	5	10	17
75	3	6	10

Table 1.8.11. Power frequency test voltages for AC motor windings

Test item	Electric motor power, kW	Rated motor voltage, kV	Test voltage, kV
1. Stator winding	Less than 1,0	Below 0,1	0,8(2U_Mr.+ 0,5)
	From 1,0 to 1000	Below 0,1	0,8(2U_Mr.+ 1)
	From 1,0 to 1000	above 0,1	0,8(2U_Mr.+1), but not less than 1,2
	From 1000 and more	Up to 3,3 inclusive	0,8(2U_Mr.+ 1)
	From 1000 and more	Over 3,3 to 6,6 inclusive	0,8 2,5U_Mr.
	From 1000 and more	over 6,6	0,8(2U_Mr.+ 3)
2. Rotor winding of synchronous electric motors designed for direct starting, with an excitation winding closed to a resistor or power source.			8 times U_Mr.excitation systems, but not less than 1,2 and not more than 2,8
3. Rotor winding of an electric motor with a phase rotor.	-	-	1,5U_р^*, but not less than 1,0
4. Resistor of the field damping circuit of synchronous motors.	-	-	2,0
5. Rheostats and ballast resistors.	-	-	1,5U_р^*, but not less than 1,0

* Ur voltage on the rings with an open stationary rotor and rated voltage on the stator.

See other articles Section Rules for the installation of electrical installations (PUE).

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