64 Unidrive M300/HS30 Quick Start Guide
Issue Number: 7
BRANCH CIRCUIT PROTECTION
The fuses and circuit breakers required for branch circuit protection are specified in the Installation
Instructions.
OPENING OF BRANCH CIRCUIT
Opening of the branch-circuit protective device may be an indication that a fault has been
interrupted. To reduce the risk of fire or electric shock, the equipment should be examined and
replaced if damaged. If burnout of the current element of an overload relay occurs, the complete
overload relay must be replaced.
Integral solid state short circuit protection does not provide branch circuit protection. Branch circuit
protection must be provided in accordance with the National Electrical Code (NEC), The Canadian
Electrical Code, and any additional local codes.
DYNAMIC BRAKING
M100, M101, M200, M201, M300 or M400, frame sizes 1 to 4 have been evaluated for dynamic
braking applications. Other drive models have not been evaluated for dynamic braking.
11.7 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 protection level is adjustable and the method of adjustment is provided in the Control User
Guide. Maximum current overload is dependent on the values entered into the current limit
parameters (motoring current limit, regenerative current limit and symmetrical current limit entered as
percentage) and the motor rated current parameter (entered in amperes).
The duration of the overload is dependent on motor thermal time constant. The maximum
programmable time constant depends on the drive model. The method of adjustment of the overload
protection is provided.
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.
11.8 External Class 2 supply
The external power supply used to power the 24 V control circuit shall be marked: “UL Class 2”. The
power supply voltage shall not exceed 24 Vdc.
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