20
Digitax HD M75X Quick Start Guide
Issue Number: 2
5.2.9
Solid state short circuit protection
Integral solid state short circuit protection is provided. However, this does not provide branch circuit
protection.
In the event of a ground (earth) fault within the drive, the input protective devices (fuses or circuit
breaker) provide overcurrent protection in the usual way. All AC drives incorporate solid state short
circuit protection. If a ground (earth) fault occurs in the motor circuit, the solid-state protection
operates, the inverter trips and all power switches (IGBTs) are switched off within a very short time,
typically less than 10
μ
s. The total trip time is unlikely to exceed 100
μ
s. In the event of failure of the
solid state short circuit protection, one or more of the inverter power devices then fails either open
or short circuit. If the failure mode is open-circuit, the fault is interrupted. If the failure mode is short-
circuit, the input protection devices (fuses or circuit breaker) clear the fault and open the circuit.
5.2.10
Motor overload protection and thermal memory retention
All drives incorporate internal overload protection for the motor load that does not require the use of
an external or remote overload protection device. The method of adjustment of the overload
protection is provided in section 4.4
Current limits
on page 17. The protection levels are expressed
as a percentage of full load current. In order for the motor protection to work properly, the motor
rated current must be entered into Pr
00.046
or Pr
05.007
. The motor overload protection levels
may be adjusted below 250 % (RFC-S/RFC-A) or 165 % (Open loop) if required. The duration of
the overload is dependent on motor thermal time constant. The drives are provided with user
terminals that can be connected to a motor thermistor to protect the motor from high temperature,
in the event of a motor cooling fan failure.
5.3
Environmental
5.3.1
Enclosure rating
All drives are Open Type.
5.3.2
Mounting
Drives may be mounted
•
Singly
•
Side by side
•
Stacked one above another when fitted with a rear vent kit
The drives are equipped with a rear vent that allows heated air to be exhausted from the rear of the
drive rather than the through the top. This mounting arrangement provides the following benefits:
•
Reduction in enclosure size.
•
Allow vertical stacking of drives.
•
Reduce the need for a secondary enclosure fan.
Refer to the ‘Mechanical Installation’ (Chapter 3) of the
Digitax HD M75X Series Installation and
Technical Guide
.
For compact multi axis installations, the rear venting kit allows drives to be vertically mounted one
above the other, where this is the case, a minimum clearance of 100 mm (3.94 in) should be
maintained between drives. A current derating must be applied to the drive if the rear vent kit is
installed. Derating information is provided in the ‘Technical Data’ (Chapter 6) of the
Digitax HD
M75X Series Installation and Technical Guide
. Failure to do so may result in nuisance tripping.
5.3.3
Operating temperature
The drives are suitable for use up to 40 °C (104 °F) surrounding air temperature. Operation up to
55 °C (131 °F) is permitted with de-rated output. Refer to the ‘Technical Data’ (Chapter 6) of the
Digitax HD M75X Series Installation and Technical Guide
.
