QOU220 SQUARE D, QOU220 Datasheet - Page 10

• Manufacturer Part Number: QOU220
• Description: CIRCUIT BREAKER, THERMAL MAG, 2P, 20A
• Manufacturer: SQUARE D
• Series: QOUr
• Type: Thermal/Magneticr

Specifications of QOU220

• Actuator Style: Toggle
• No. Of Poles: 2
• Current Rating: 20A
• Voltage Rating Vdc: 48V
• Voltage Rating Vac: 240V
• Mounting Type: DIN Rail
• Actuator Type: Handle
• Brand/series: QOU Miniture — Low Ampere
• Number Of Poles: 2
• Special Features: Visi-Trip® Trip Indicator
• Voltage Rating: 120/240 V
• Leaded Process Compatible: No
• Rohs Compliant: No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

QOU Miniature Circuit Breakers and Switches
Application Information
Figure 3:
Figure 4:
10
1.0
.9
.8
.7
.6
.5
Current Rating in Amperes
160
150
140
130
120
110
100
0
© 2005 Schneider Electric All Rights Reserved
90
80
70
60
50
40
30
20
10
(14)
-10
100
QO,
QOU
(32)
0
Ambient Temperature ˚C
Ambient Rerating of QOU Circuit
Breaker
Frequency Rerating of QOU
Circuit Breaker at 400 Hz
200
(68)
20
300
(104)
40
(˚F)
(140)
60
125 A
110 A
100 A
60 A
45 A
40 A
30 A
20 A
10 A
90 A
80 A
70 A
50 A
15 A
For example, Figure 3 shows the ambient rerating curves for QOU miniature
circuit breakers. What is the continuous current capacity of a 80 A circuit
breaker applied at 104° F (40° C)? A 90 A circuit breaker at 50° F (10° C)?
By finding 40° C on the horizontal axis and reading up to the 80 A curve, you
find that the circuit breaker will carry 80 A, which is its rated current carrying
capacity. If the circuit breaker will be used on a continuous load (defined as
three hours or more), Section 210-20(a) of the 2005 NEC requires that
loading not exceed 80% of the rating. Here, 80 A x .80 = 64 A.
Locate 50° F (10° C) on the horizontal axis and move straight up to the 90 A
curve. The circuit breaker will carry 110 A. Again, if the circuit is used on a
continuous load, it must be applied at 80% of its rating. In this example the
equation is 110 A x .80 = 88 A.
As explained in Section 210-20(a) of the NEC:
Frequency Rating
The standard-rated frequency for circuit breakers is 60 Hz, but Square D
circuit breakers can be applied on 50 Hz systems without thermal or
magnetic rerating. Other frequencies can affect the thermal, magnetic and
short-circuit tripping characteristics of circuit breakers.
Applying thermal-magnetic circuit breakers at frequencies above 50/60 Hz
requires special consideration of the effects of high frequency on circuit
breaker tripping characteristics. Thermal and magnetic operations must be
treated separately.
Thermal Tripping Performance at High Frequency
At frequencies below 60 Hz, the thermal rerating of thermal-magnetic circuit
breakers is negligible. However, at frequencies above 60 Hz, thermal
rerating is required. High-frequency operation causes abnormal heat rise in
the current-carrying parts because of the skin effect.
One of the most common high-frequency applications is at 400 Hz. Figure 4
indicates the thermal rerating multiplier to be used with each circuit breaker
family when applied on 400 Hz systems.
When applying a 100 A QOU circuit breaker on a 400 Hz system, the circuit
breaker’s current carrying capacity is as follows:
•
•
.
“Where a branch circuit supplies continuous loads or any combination of
continuous and noncontinuous loads, the rating of the overcurrent
device shall not be less than the noncontinuous load plus 125 percent of
the continuous load.
“Exception: Where the assembly, including the overcurrent devices
protecting the branch circuit(s), is listed for operation at 100 percent of
its rating, the ampere rating of the overcurrent device shall be permitted
to be not less than the sum of the continuous load plus the
noncontinuous load.”
Non-continuous Loads (less than three hours): Using Figure 4, the QOU
circuit breaker may be applied at .78 of rating, or 78 A.
Continuous Loads (three hours of more): NEC Article 210-20(a) requires
that standard circuit breaker loading does not exceed 80% of the circuit
breaker’s rating when used for continuous loads. Therefore, the current-
carrying capacity of a 100 A QOU circuit breaker operating under
continuous load at 400 Hz would be 100 A x .78 x .80 = 62 A.
09/2005