vfd, installations?

[pilot]

hi everyone
just was wondering if a hard wired stop start station was required when installing a vfd,
Iknow that the rule of thumb was to hard wire a stop start p/buttons for plc arrangment but not sure about the variable frequency drives,anybody know what it should be ? or even must be?

thanks alot

[Tony Moscioni]

CSA Standard Z432-94 Reaffirmed in 1999 "Safeguarding of Machinery"

7.6.3 Emergency Stop Devices in Programmable Electronic Systems

Emergency stop devices, as defined in Clause 7.3, shall be hardwired and not affected by, or routed through, the programmable system. The emergency stop devices may be monitored through the programmable system.


Ontario Electrical Safety Code

Rule 28-502 Control Location

A motor controlled manually, either directly or by remote control of a motor starter, shall have the means of operation of the controller so located:

(a) That safe operation of the motor and the machinery driven by it is assured, or the motor and the machinery shall be guarded or enclosed so as to prevent accidents due to contact of persons with live or moving parts; or

(b) Where compliance with Paragraph (a) is not practicable because of the type, size, or location of the motor or machinery and its parts, devices shall be provided at each point where the danger of accidents exists whereby the machine or parts of the machine may be stopped in an emergency.

Rationale for Rule 28-502. Exposed live and moving parts may be unsafe to personnel.

Intent for Rule 28-502. When safe operation of the motor and machinery cannot be assured because of the location of the control equipment, we intend to require that exposed live or moving parts be guarded against personal contact. If this is not possible, we intend that devices be provided at each danger point to allow the motor or machinery to be stopped in an emergency.

Separate E-Stops that are not hard wired and part of the PLC will not always work, because if for some reason the software fails, the equipment depending on the failure mode might keep on operating.

Tony Moscioni
Electrical Inspector
Electrical Safety Authority